Vegetable gardening in the days of COVID-19, and beyond

An extended period of home isolation might be necessary in the near future to minimize the rapid spread and devastating consequences of the new coronavirus pandemic.

Last week, I recommended vegetable gardening as a way to cope with the stress of social distancing and as a source of healthy food and safe outdoor activity. That topic deserves more attention, given the growing concerns about COVID-19.

In this time of uncertainty, growing fresh annual vegetables and melons at home might be anything from a productive form of outdoor activity to a much-needed source of nutrition for your family and for others in need. Growing food at home is very satisfying, and it also helps reduce trips to the grocery store.

Whether you have a large backyard or just a sunny balcony, it’s possible to grow even a small number of food-producing plants. The basic requirements are good soil, water, a source of nutrition (worm castings, compost, or commercial vegetable fertilizers), and direct sun exposure of at least 6 to 8 hours each day.

Japanese eggplants interplanted with marigolds for pest control and a splash of color. (Photo by Kathy Ikeda)

If you’ve never grown vegetables at home before, or would like to become better at it, here are some excellent resources:

  • San Joaquin Master Gardeners’ “Home Vegetable Gardening” website: This page has links to a locally appropriate and easy-to-read vegetable planting guide, a University of California publication entitled “Vegetable Gardening Basics,” information on growing vegetables in containers, and much more.
  • The University of California’s Integrated Pest Management (UC IPM) webpage for vegetables and melons: This site is organized by type of plant—beans, carrots, corn, peppers, squash, tomatoes, and so on. Each page provides not only pest control tips for each plant, but also a whole range of valuable cultural care information: planting, watering, fertilizing, harvesting and storage, and much more.
  • What’s Growing On, the blog by San Joaquin Master Gardeners (SJMGs): Most of our past articles are accessible on this website, as a public service provided by SJMGs and The Record, and many are about vegetable gardening and related topics.

Seeds are one way to start growing vegetables now, in preparation for summer or fall harvests. Some food plants—such as beans, carrots, corn, melons, squash—are ideal for April planting from seed, and they should be planted in the ground where they are to grow. This is called “direct seeding,” and it’s the easiest planting method. 

Other vegetable seeds can be started indoors or in a greenhouse. This method is usually used with tomatoes, peppers, and eggplants, which can be started indoors from seed as early as January and February (when temperatures are too cold outside for proper seed germination and growth). It’s a bit late in the season to start these seeds now, but you can give it a try. 

Leftover plastic containers from earlier plant purchases—especially six-packs and 4-inch pots—work well for starting vegetable seeds. Improvised seed-starting trays can also be made out of rigid plastic produce containers, the ones pre-punched with ventilation holes; their lids help retain some humidity, which helps keep soil moist. Before starting seeds in old or pre-used containers, sterilize them by submerging them in a mild bleach solution (one part bleach to nine parts water), rinse them with lukewarm water, and allow them to dry before filling them with a seed-starting mix. Then, plant seeds according to the instruction on the packets. 

After your vegetable seeds sprout and grow to an adequate size (a minimum of two sets of mature leaves), they can be transplanted into the garden after a “hardening off” period. This means gradually exposing them to ever-increasing increments of direct sun exposure over a period of about two weeks.  

You can help support our local economy by buying seeds or seedlings from area nurseries and garden centers. Call in advance to verify their hours of business—since they might be modified or even closed due to virus-related concerns—and to check their availability of vegetable seeds or seedlings. Or, order seeds online and have them delivered to your home.

Vegetable plants—especially root vegetables like carrots, beets, and potatoes—prefer loose, deep soil that’s rich in organic matter. If you have heavy clay or sandy soil, amend it with compost to help assure your vegetable plants’ health and vigor.

Once your plants start growing in earnest, make sure they get adequate water. Vegetables prefer consistently moist soil, and tomatoes and peppers are particularly susceptible to damage from inconsistent watering. Also, most vegetable plants don’t like water on their leaves (it encourages fungal growth), so avoid overhead sprinklers and use a ground-level hose or drip irrigation. 

Another growing tip: avoid using pesticides. Home vegetable gardening is the easiest way to obtain fresh produce free of chemical contamination, and most common pests can be eliminated with non-toxic methods. Chewing damage from caterpillars, such as cabbage loopers and tomato hornworms, can be minimized by inspecting plants and picking off any invaders by hand. Aphids, which like to congregate on and suck juices from the leaves of many vegetables, can simply be sprayed off with a strong stream of water. Earwigs can be caught at night in rolled-up newspaper, then disposed of in the morning.

Once your plants start bearing their much-awaited edibles, it’s time to enjoy! Even non-traditional parts of some vegetable plants can be eaten. Beets, Brussels sprouts, and pea greens are a few favorite examples in our family. The leaves of these plants aren’t usually seen in grocery stores, but they’re perfectly edible. Once washed, they can be julienned and added to a salad, or chopped and lightly sautéed with olive oil and some seasonings for a delicious side dish. But be cautious. The leaves of some vegetables contain toxic compounds and should not be eaten, so be sure to check a reputable source before eating atypical parts of a plant.

A basket full of unique and decorative “Michael Pollan” tomatoes, named after the well-known author (Photo by Kathy Ikeda)

If you end up having a larger harvest than you can use, you can preserve many kinds of vegetables by canning them. An important note: home canning must be done in a way that eliminates the possibility of botulism, a serious and often fatal illness. It’s caused by a species of bacteria (Clostridium botulinum) that produces an extremely potent toxin; contamination can be prevented by proper sterilization and heating processes.  If you have canning-related questions, you can find information here:

Finally, this is a perfect time to share the bounty of your garden. Give some vegetables or fruits to your house-bound, elderly neighbors. Donate your excess produce to local food banks, senior centers, and homeless shelters. Maybe even support a local, independent restaurant, by helping reduce their costs for purchasing fresh vegetables. (Call any organization or business first—before dropping off fresh foods—to see if your produce will meet their needs, and to avoid potential waste or other problems.) Use your personal vegetable gardening project to strengthen our community, both now and for the long term.

Wishing you good health and happy growing!

For gardening-related questions, call the UC Master Gardener office at 209-953-6112, or visit our website

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The value of gardens and gardening in trying times

This is truly an unprecedented period in the history of our country and our world. The sudden development and rapid spread of the COVID-19 coronavirus is upending lives around the planet, and our normal lives and customary routines have been put on hold for the foreseeable future.

This column is supposed to be garden-related, but before I delve into that topic, it’s important to acknowledge my fellow human beings’ stress and grief. To anyone struggling with isolation, loss of job or income, disrupted school schedules, or other difficult circumstances, I wish you strength and the hope that your needs will be soon be met. To those who are ill with the novel coronavirus, I wish you a quick and complete recovery. To all the medical professionals who are providing virus testing and caring for infected patients, and to others whose important and ongoing work puts them in harm’s way, I send wishes for your good health and a message of profound gratitude. And to anyone who has lost a loved one as a result of this pandemic, my deepest and most heartfelt sympathies.

Whatever your circumstances are in this moment, my hope is that gardens and gardening can help in some way.

Elephant sculptures amid beautiful blooms at the Clovis Botanical Garden, February 2020. Their raised trunks are symbols of good fortune, a timely wish for all. (Photo by Kathy Ikeda)

Gardens and natural environments are very therapeutic. Simply being outdoors amidst fresh air, sunshine, and greenery can reduce stress, alleviate depression, lower blood pressure, and increase our bodies’ production of vitamin D. Caring for plants is a wonderful source of physical activity, and it also stimulates the mind. Self-care is particularly important now, and gardening is one cheap and easy way to fulfill part of that need.

Rather than thinking of “yard work” as a necessary drudgery, try focusing on its health-giving benefits. Any stay-at-home time spent pruning, weeding, or planting is helping keep you fit and strong. And, if your time and energy level allows, why not try a fun and rewarding mini-project? If you have some favorite perennial plants, try propagating them by taking stem cuttings, treating them with rooting hormone, and planting them in moist, sterilized potting mix. If you have an unused/underutilized area or an unwanted patch of grass, start planning now to replace it in fall with California natives; this will help support local pollinators and restore a bit of natural habitat. Or, plant a tree or shrub to honor a loved one.

Vegetable gardening is yet another rewarding and productive pursuit during this time of recommended “cocooning.” You might recall that residents of the U.S. and other countries were encouraged to plant their own Victory Gardens during World Wars I and II and other periods of national crisis and solidarity. Now—as then—vegetable gardens can provide healthy physical activity, a morale boost, and an inexpensive source of nourishment in the days and weeks to come. March and April are ideal months to plant seeds of summer crops such as beans, carrots, corn, eggplant, melons, peppers, squash, and tomatoes. For those with school-age children, this is an opportunity to teach them where their plant-based food comes from and how to grow it. Consider sharing share seeds and harvests with your loved ones and neighbors while developing a healthy, long-term habit of growing your own food. You can find locally appropriate vegetable gardening resources at

While spending time inside your home, houseplants can be a source of joy. Their greenery beautifies rooms, and in some circumstances they help purify and oxygenate indoor air. Ornamental plants are truly a form of horticultural therapy; they’ve been proven to aid in recovery from sickness, and having plants nearby helps improve human memory, concentration, and productivity. This is an excellent time to learn more about caring for each of your indoor plants; to repot them with fresh planting mix; to give them a spring feeding with worm castings, compost, or fertilizer; or to gently bathe them and clean their leaves of accumulated dust.

Outdoor exercise is another great coping strategy, and it’s still allowed under current statewide COVID-19 guidelines. If you live near a public park or garden, plan a short visit for some physical activity and relaxation. However, do so cautiously, and remember to keep a safe distance from others so that you don’t expose yourself or them to unnecessary risk. Stay close to home, and be sure to check ahead of time about open hours and restrictions. Two small and close-at-hand public gardens are the native plant garden at the Oak Grove Nature Center and the Learning Landscape outside the San Joaquin Master Gardener office.

I hope that you can use gardens and gardening to help maintain your health in the coming days and weeks, within the limitations of prudent social distancing. Please be sure to follow any current and developing state and federal COVID-19 recommendations and orders, to ensure the safety of your family, friends, and the community at large. We’re all in this together.

As an additional public service, please refer to these reputable sources of information regarding COVID-19:

For gardening-related questions, call the UC Master Gardener office at 209-953-6112, or visit our website:

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Growing Dahlias is hard work but very rewarding.

I have grown dahlias for a lot of years and I am still learning how to be successful at propagating this plant from tubers. Dahlias come in various nuances of colors, sizes, and forms and they bloom starting in June continuing to November. Last year I had about 150 Dahlias. They are a bit perplexing and difficult at times, but the rewards are so great that the effort to deal with these cantankerous tubers is worth it.
One good thing about living in California, you don’t have to dig your dahlia tubers to keep them from freezing like my mother used to do where I grew up in New Jersey. My mother only had a few dahlias and perhaps digging a few and storing them in the cellar each year was enough of a workout.
I am hard-pressed to dig all the dahlias that I grow. Last year I dug all of them, but this year I dug only half. It is a chore to wash off the black adobe clay from the tubers, label and store them in wood shavings until this spring when they will be divided to replant or give away. Dahlias tubers left in the ground over the winter are well established and know when to start growing and they bloom sooner than newly planted tubers. If you like early blooms, and who doesn’t leave some in the ground. The downside of not digging them is that some may rot if the winter is particularly wet which is not the case this winter. Hence I am hoping that the four rows I didn’t dig will be blooming early.
Tubers should be planted 2-3 feet apart with 4 feet between rows to allow access. They will need to be staked and tied as they grow, so best to plant the stake at the same time that the tuber is planted so the tuber is not impaled by the stake if done later. Tomato cages can also be used to confine the plants. I like to mix compost into the planting hole which enhances growth without chemical fertilizers. Just planted tubers should not be watered heavily but once plants are growing about 1 inch of water per week is good. I use a drip system with 2 GPH emitters and water for an hour every other day or about 6 gallons per plant per week.
Unfortunately, there are always pests lurking to ruin your dahlia garden. When the first shoots appear they are food for snails, slugs, and earwigs. These pests can be thwarted by using snail and slug bait. If you have pets the best bait contains iron phosphate which unlike metaldehyde baits will not harm your pets. You can also deplete the population by hunting them by flashlight at night. Earwigs can be thwarted by placing some diatomaceous earth in a ring around the young shoots or they can be trapped using tuna fish cans or cat food cans with ¼ inch of oil preferably fish oil in the bottom with the cans buried at ground level. It is also a good idea to deny them hiding places beneath boards or mulch if possible.
Later in the season, the pests are thrips and spider mites. When you want to enjoy the blooms these critters want to enjoy the dahlia leaves. I found that spraying the foliage with water helps control their abundance as mites don’t like moist conditions and they along with thrips can get washed off. Insecticidal soaps and Neem oil solutions can also be used. It is good to stay on top of this or the plants will suffer and blooms will be less too. It is also good to keep a sticky trap in the garden to monitor for thrips abundance and keep on top of it. For more information on pest control see:
Keep flowers deadheaded or preferably your vases full. To encourage larger blooms it is good to disbud the two side buds and leave the main bud. It also a good idea to head cut the new plant at 12 inches to encourage early-branching which will result in more blooms later. It is also good to thin older well-established dahlias if there are many weak shoots they should be removed to enhance energy going to the main stems.
More info and videos on dividing and storing Dahlias is at Swan Island Dahlias at: Happy dahlia gardening.

If you have a gardening related question you can contact the UC Master Gardeners at 209-953-6112. More information can be found on our website:

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Zinnias are great to grow for summer blooms.

Zinnias are the work horses of the cutting flower garden. They are easy to grow and have a short time from planting to bloom time. They attract bees, butterflies and hummingbirds so are a great addition to a pollinator-attracting garden. I have done some flower show judging at fairs and the first time that I judged zinnias at the Big Fair in Fresno I was amazed at the variety of zinnias as I had only known a few cultivars of Zinnia elegans. There are other species but insufficient room here to describe them all.

Zinnias require rich, well-drained soil in full sun. Zinnias do best when kept evenly moist, and you can feed them with compost or a balanced fertilizer every few weeks for best flower production. For extended bloom, deadhead plants throughout the season or just keep all your vases full. Remove unsightly leaves to prevent the spread of disease and to keep plants looking healthy.

They evolved in the warm climate of Mexico so they are heat and drought tolerant but not frost tolerant and should not be set out before frost time is past. They are best planted after night temperatures reach above 50 degrees F. You can get a head start on the blooming season by starting the seeds indoors or in a greenhouse 4-6 weeks before planting in the garden. Seeds should be planted about 3 inches apart. A sunny windowsill will work and germination takes about 6 days.

Seeds can also be sown directly in the garden; 1⁄2 inch deep with 2- to 3-inch spacing in rows 12 inches apart in well-worked, fertile garden soil in full sun. Gently firm the soil and then keep it evenly moist while awaiting germination. When seedlings become large enough to handle, thin them to 10 to 12 inches apart. In the garden, it is good to provide for air circulation to minimize infection with powdery mildew. Zinnias come in a wide range of colors (except blue) from lime green, red, yellow, pink, orange to white. You can usually purchase a mix of colors or a one-color selection. They also come in a multitude of forms and sizes as described below. Hence they can fit a lot of garden spots from containers to front and back borders.

Petite: ‘Thumbelina’ zinnias generally don’t grow more than 4-6 inches and come in all the colors of the rainbow in a compact, versatile plant that is good in border fronts or containers. ‘Pepito’ and ‘Button Box’ seeds produce dwarf plants that are 10 inches tall. ‘Profusion’ zinnia series is a hybrid of (Zinnia angustifolia x Z. elegans) and it is a low growing choice especially for containers or mass planting. The two-inch flowers are single or semi-double and daisy-formed which cover 12 to 15-inch mounding plants. This All-America Selections award-winning series has cultivars that come in shades of orange, cherry, white, and apricot, all of which partner well with other colorful plants. Profusion zinnias are highly disease resistant and require little maintenance because they are self-cleaning; dropping their blossoms after they fade.

Small: ‘Lilliput’ are 18-24 inches with blooms that are small, round bauble-like that add interest and texture to your garden, or flower arrangements.  ‘Pulcino’ produces 18-24 inch, bushy plants that are early and prolific flowering with double and semi-double blooms. It is also known as ‘Cut and Come Again’ zinnia. 

Medium: ‘Scabiosa’ has finely textured blooms on plant 30 inches tall. ‘State Fair’ has 5-6 inch, double-flowered blooms and a bounty of colors on 30-inch robust plants that are great for cutting and enjoying in the vase.  ‘Peppermint Stick’ zinnias grow to 30 inches and are uniquely striped like a holiday peppermint. ‘Oklahoma’ series are 30-40 inches and can be obtained in several individual colors from white, pink, salmon, scarlet and gold. The flowers are 1.5 to 2.5 inches in diameter.

Large:California Giants’ are 48 inches with flowers 5 inches across; a very productive, large plant for the cutting garden. ‘Benary’s Giant’ zinnia is an award-winning variety producing large 4-5 inch diameter fully double flowers on sturdy 40-48 inch branching stems. ‘Dahlia Flowered’ zinnia grows to 40 inches and has fully doubled flowers 4-5 inches in diameter with tightly packed petals that bend downward slightly at the ends. They were developed in 1919; so definitely an heirloom. ‘Gift’ is an heirloom zinnia that is a Russian contribution with all red color and 36 inches tall with 3-4 inch flowers—a favorite of mine. Happy zinnia gardening!

If you have a gardening related question you can contact the UC Master Gardeners at 209-953-6112. More information can be found on our website:    

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It’s time to plan for spring garden events

Spring is a busy time for garden-related happenings in San Joaquin and neighboring counties. There’s something happening nearly every weekend between now and summer, and with so many events to choose from, there are plentiful opportunities for fun and enriching outings. Consider taking advantage of these upcoming events to expand your knowledge, buy new water-wise plants, view beautiful and inspirational gardens, and more:


Classes by UCCE Master Gardeners of San Joaquin County

When:      Various dates

Where:     Various locations


Your local Master Gardeners have a wonderful series of free classes planned for spring this year. Dates and locations vary to encourage attendance throughout the county. See the Calendar of Events on the right side of our website’s home page, and click on “Show More” for additional details. Upcoming classes include “All About Tomatoes” (February 25), “Creating Your Summer Vegetable Garden” (March 9), “Planning Your Summer Vegetable Garden” (March 16), and “Summer Vegetable Garden Above the Ground” (March 24). Space is limited; call 209-953-6100 to reserve a space.


2020 Smart Gardening Conference

When:       Saturday, March 14 from 8:15 a.m. to 4:10 p.m.

Where:     Robert J. Cabral Agricultural Center

                  2101 E. Earhart Ave., Stockton


This conference by the UCCE Master Gardeners of San Joaquin County features a choice of 20 garden-related presentations, to be held in two morning and two afternoon sessions. This year’s featured speaker is “Plant Lady” Marlene Simon, horticulturalist and garden columnist for the Sacramento Bee. A few presentations will be given by the local Master Food Preservers. More details to come in next week’s article!


Fair Oaks Horticulture Center Open Garden Days

When:       Saturday, March 14 from 9:00 a.m. to noon

                  Wednesday, April 15 from 9:00 a.m. to noon

                  Saturday, May 9 from 9 a.m. to noon

Where:     11549 Fair Oaks Boulevard, Fair Oaks


This center is the demonstration garden for the UCCE Master Gardeners of Sacramento County, and it boasts a water-efficient landscape, a composting area, an irrigation display, and an expansive edible garden. Each monthly event features several different, free mini-demonstrations by knowledgeable presenters. These are rain-or-shine, outdoor events.


UC Davis Arboretum Plant Sales

When:       Saturday, March 14 from 9:00 a.m. to 11:00 a.m. (members only)

                  Saturday, March 14 from 11:00 a.m. to 1:00 p.m. (public sale)

                  Saturday, April 4 from 9:00 a.m. to 1:00 p.m. (public sale)

                  Sunday, April 26 from 9:00 a.m. to 1:00 p.m. (public sale)

                  Saturday, May 9 from 9:00 a.m. to 1:00 p.m. (public clearance sale)

Where:     UC Davis Arboretum Teaching Nursery

                  Garrod Drive (across from the Veterinary School), UCD campus, Davis 


The semi-annual sales at this one-acre nursery feature a huge variety of offerings, including reliable California natives and plants on the Arboretum All-Stars list — those species specifically recommended for planting in the Central Valley. Arrive early for the best selection; these sales attract many visitors. View the plant sale inventory at Arboretum members (including anyone who joins during the sale) receive a discount on purchases. While you’re in the area, take time to look at the beautiful, water-wise landscaping at the nursery, visit the adjacent Mary Wattis Brown Garden of California Native Plants, or wander the Arboretum pathways along Putah Creek. 


CNPS Spring Native Plant Sale

When:       Saturday, April 4 from 9:00 a.m. to 2:00 p.m.

Where:     Elderberry Farms Native Plant Nursery

                  2140 Chase Drive, Rancho Cordova


This semi-annual sale by the Sacramento Valley Chapter of the California Native Plant Society (CNPS) features a wide variety of California native perennials, shrubs, and trees. CNPS’s spring sale is held at Soil Born Farms on the American River Parkway, which features attractive native plants gardens and wildlife-friendly hedgerows (an example of conservation-based agriculture). Admission is free; proceeds from this event support CNPS’s educational and conservation work.


Gardens Gone Native

When:       Saturday, April 25 from 9:30 a.m. to 4:00 p.m.

Where:     Gardens throughout Sacramento and Yolo Counties


This free, inspiring, self-guided tour by Sacramento CNPS features different residential landscapes planted at least 50% with Northern California native plants. (Many gardens also include compatible water-wise plants from Mediterranean regions.) Online registration is required. A list of garden locations will be provided to registered participants closer to the tour date; every participant selects their own route and which gardens to visit. Learn how to support native pollinators and wildlife, reduce water and pesticide use, and encourage beneficial insects while meeting enthusiastic tour hosts.


San Joaquin Master Gardener Open Garden Day and Plant Sale

When:       Saturday, April 18 from 9:00 a.m. to noon

Where:     Robert J. Cabral Agricultural Center

                  2101 E. Earhart Ave., Stockton

This event showcases the UCCE Learning Landscape, a demonstration garden created and maintained by the UCCE Master Gardeners of San Joaquin County. Explore the different sections of the garden (Mediterranean, California native, pollinator, edible, and more) and get gardening-related advice from our many on-site volunteers. Offerings at the plant sale will include vegetable seedlings, culinary herbs, a variety of perennial plants, some California native plants, and a nice selection of easy-care succulents. A plant list will be posted online closer to the date of the event.

A colorful scene from a past regional garden tour, with a whimsical sculpture and many beautiful California native plants. (Photo courtesy of Kathy Ikeda)


Bringing Back the Natives Garden Tour

When:       Sunday, May 3 from 10:00 a.m. to 5:00 p.m.

Where:     Various locations in Alameda and Contra Costa Counties


This is another self-guided garden tour. Pre-registration is required, a $10 fee is charged for the garden guide, and a donation of $15 per person is suggested to help cover event costs. Garden access will only be granted with the tickets included in the paid garden guide.

This year’s tour showcases 35 private gardens and several East Bay California native nurseries. Garden sites for this tour are divided into two categories: “Bayside Cities” and “Inland Cities.” Be sure to visit gardens in the latter category if you’re looking for inspiration, since the weather pattern in inland Bay Area cities most closely matches the hot-summer climate in our area. Visit the website to register, view the tour flyer, and access photos and other helpful information. 

For gardening-related questions, call the UC Master Gardener office at 209-953-6112, or visit our website:

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Reveling in warmth, hoping for cold

I enjoy mild winter weather as much as the next person. It’s so refreshing to emerge from the house on an unseasonably warm and dry day and bask in the sun’s rays while catching up on garden chores. 

People tend to think of cold weather as inconvenient at best and damaging at worst. Frigid days and nights lead to chilly hands and feet, higher heating bills, and other nuisances. In our gardens, predictions of overnight frost or deep freezes mean that we need to protect our cold-sensitive citrus trees, tender perennial plants, and outdoor pipes from damage.

Cold days might be unwelcome, but the horticulturalist in me yearns for more of them. Why, you might ask?

Cold temperatures are an essential element of the Northern California climate, and they’re actually beneficial to our native plants, many favorite perennials, and orchards. The natural yearly progression from warm weather to cold and back again triggers biochemical responses in plants that regulate their growth cycles. Cold weather is one signal that plants heed to begin their winter rest period, called “dormancy.” Like people, plants need their sleep.

The dormant period begins in the fall when the day length shortens and temperatures decrease. These changes prompt deciduous plants to drop their leaves and produce growth-inhibiting hormones. Those hormones prevent the plants from “leafing out” during the winter, even if there are periods of unseasonably warm weather. This chemical mechanism protects the plants by delaying the growth of tender new leaves, which would be damaged if the weather suddenly turned cold again. The dormant period is broken only when the plant experiences a cold spell of sufficient length to break down the hormones. This process is often referred to as chilling or vernalization. 

Such chilling is also essential to our local agricultural production. Temperate fruit and nut trees — those species that go dormant in winter but can’t survive extreme cold — need a specific, cumulative number of chill hours where temperatures are between 32 and 45 degrees Fahrenheit. Without adequate and consistent cold weather, their productivity can suffer tremendously: leaf bud growth and development will be delayed, flower buds will drop or be poorly formed, flowering can be prolonged (thus making blooms more susceptible to diseases), and fruit set will be reduced.

Some common orchard trees have high chill requirements. Depending on the variety, walnut trees need 500 to 700 chill hours to break dormancy. The ever-popular Bing cherry needs 900 chill hours to effectively bloom and set fruit. And the Bartlett pear, which comprises roughly 75% of the world’s pear production, needs a whopping 1500 chill hours each winter! On the other hand, almonds, figs, olives, pecans, and persimmons have relatively low chill needs. To read more about this topic, see the University of California’s online publication, The California Backyard Orchard, “Tree Selection” (

A Manteca almond orchard in full and glorious bloom. (Photo by Kathy Ikeda)

Chill hours are one set of data recorded throughout the state by the California Irrigation Management Information System (CIMIS). Our local CIMIS station is located in Manteca, and during the 2018-2019 winter season — measured from the first day of November to the last day in February— it recorded 924 chill hours. During the unseasonably warm winter of 2014-2015, we had only 723 chill hours.

As of February 9 this year, San Joaquin County has an accumulated winter total of 881 chill hours. That might sound adequate, but other factors come into play as well. When cold weather is interrupted by periods of several consecutive days of warm, sunny weather, the cumulative seasonal chilling requirement can increase. Spring-like weather during winter essentially offsets some of the prior chill hours. According to the Master Gardener Handbook, “Cloudy or foggy weather that maintains temperatures below about 60°F during the day and 45°F at night is often necessary in parts of California to achieve adequate chilling hours.”

For the sake of our plants, we should rejoice in a normal season of cold winter weather.

With the certainty of warming trends due to climate change, home orchardists might want to plan ahead when selecting new fruit or nut trees. Consider planting types with naturally low chill needs, or buy fruit varieties specifically bred to have “low chill” requirements — 300 hour or less of temperatures below 45 degrees F. (Low-chill cherry cultivars have only been developed in the last couple decades.)

If we do get more near- to below-freezing temperatures this year, here are a few tips on caring for cold-tender plants:

  • Move sensitive potted plants indoors or to a protected area (under a patio cover or overhang, or against a wall that’s warmed by the sun).
  • Keep in-ground and potted plants well watered, because dry plants are more susceptible to cold damage.
  • Drape old-style Christmas lights over citrus trees and other tender plants. Unlike the newer styles of bulbs, old incandescent bulbs generate enough heat to provide a measure of protection from the cold.
  • If plants are damaged by frost, don’t remove any dead or dying growth until the risk of freezing weather is past, because the damaged leaves and stems will help insulate and protect the still healthy parts of the plant.
  • Once it’s safe, prune away all damaged parts. Dead growth will be spongy or limp, and if the bark is gently scraped away from a part of a dead stem, the color below will be black or brown. On the other hand, living tissue will be firm, and a thin layer of green will appear below the bark.
  • Avoid pruning live plants too early or heavily, because that could stimulate them to produce new, cold-sensitive growth. 

For gardening-related questions, call the UC Master Gardener office at 209-953-6112, or visit our website

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Growing common herbs is best done by your back door.

If you like cooking with fresh herbs you can easily grow many of your own in containers or in the garden. This is much more convenient than going to the store because a recipe you want to try dictates this or that fresh herbal ingredient.  Starting herbs from seed is not difficult, but purchasing young plants at plant sales or a nursery is also an option. Every year I grow parsley, culinary sage and basil from seed for myself and for plant sales. Herbs like full sun and tolerate drought as most are native to Mediterranean climates. They also don’t need rich soil or a lot of care.

Basil is easily started from seed either in the greenhouse in early spring or later in the garden and there are various cultivars available. It is must-use-herb for many dishes.

Parsley (Petroselinum crispum) is a biennial herb of two types, Italian flat-leaf, and curly leaf parsley. The Italian flat-leaf is used for a variety of flavoring whereas the curly leaf is more often used as a garnish. Parsley seeds can be soaked overnight to facilitate germination which is slow. Plant seeds in the greenhouse 8-12 weeks before frost date at a soil temperature of 70 ºF. 

Culinary sage (Salvia officinalis) is a leafy green herb of which there are golden and purple variants if you desire more color. Seeds are planted about 1/8 inch deep and best started in February and take about 2 weeks to germinate. Soil temperatures should be 60-70 ºF. It can also be started by cuttings or layered. It is used to flavor meatloaf, stuffed pork roasts and turkey stuffing, soups and stews.

Culinary thyme (Thymus vulgaris) is a low, woody perennial, highly aromatic Mediterranean herb. The three most common varieties of culinary thyme are French, lemon, and caraway. It does well in somewhat dry, sunny conditions. It holds its flavor in cooking and blends well with the flavors of its native region, such as garlic, olive oil, and tomatoes. It can be grown from seed or propagated from cuttings.

Cilantro (Coriandrum sativum) also known as Chinese parsley is a very popular herb in Mexican cuisine and it can be grown from seeds usually planted in succession as the plants tend to bolt to seed rather quickly. If you really like Mexican food and cilantro, then it might be worth your effort to plant it over and over again. There is a slo-bolt variety, but slo-bolt isn’t no-bolt. If you don’t catch it before going to seed, no worries, the seeds are coriander another useful spice for breads, Asian, Middle East and Latin dishes as well as pickling.

Oregano is an herb used commonly in Italian, Morrocan and Mexican cuisine. There are several species and cultivars; Mediterranean or common oregano (Origanum vulgare), and a variant —Origanum vulgare Aureum, golden oregano; Greek (Oregano heracleoticum).  Mediterranean oregano can best be grown from seeds in late winter in the greenhouse with bottom heat and a soil temperature above 60 degrees. Germination takes about 7-14 days.

Sweet Marjoram (Origanum majorana) is a milder sweeter tamer version of oregano. It is started from seed much as oregano.

Rosemary (Rosmarinus officinalis) can be started from seed but is more easily propagated by using cuttings taken from a neighbor or friends plant. Rosemary seeds can take 3 months to germinate so not an easy method to pursue. Rosemary cuttings are best taken in the spring or summer when actively growing. Cuttings of young growth work best. Cuttings can be 4-8 inches long; the leaves are stripped off the lower two-thirds of the sprig leaving at least several leaves.

I use rooting hormone a powder that can be dipped into and then tapped off of the rooting portion of the twig. Rooting hormone is not absolutely necessary, but a good practice. With a pencil make a hole in the well-draining potting medium in the pot and place the rosemary cutting in the hole and then tamp down the medium. This will help keep the root hormone on the cutting.  

Water and drain well and then place a plastic bag over the pot to keep the cuttings moist and place in indirect light. When growth is observed, either by roots coming out the bottom of the pot or by tugging on the cuttings to see if rooted, it is time to plant in a larger container or in the garden. Rosemary makes a reliable shrub in the landscape. For more on herb propagation see:

Tarragon (Artemisia dracunculus) is an herb grown for its aromatic leaves and is used to flavor dishes and is popular as flavoring for vinegar. Most tarragon cultivars can be grown from seed in the greenhouse but French tarragon, which has an especially desirable anise-like flavor, is one of those rare plants that is not grown from seeds. It must be grown either from cuttings or bought from a nursery.

May your future include growing delightful herbs.

If you have a gardening related question you can contact the UC Master Gardeners at 209-953-6112. More information can be found on our website:  

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Seed starting time is here.

Winter is still with us, but it is time to think about the plants that we will plant this spring. Three that immediately come to mind for me are tomatoes, eggplant and peppers, a trio of vegetables in the Solanaceae family that are widely planted for summer cuisine. All are tropical plants and thrive in warm weather and they do best with long growing seasons. Hence the seeds need to get planted from mid-January to early February so that the plants are the right size to get off to a good start for early backyard tomatoes. Last year, I bought a greenhouse, but not in time to use it for last year’s seed starting.  Hence I am initiating my seed starting this year in the comforting environment of a bright warm greenhouse.

I still marvel at what happens when these little seed packets of stored DNA are planted. They are genetically programmed to replicate the species or variety as they burst forth with roots and shoots from the little embryo inside. All they need is the proper conditions of moisture, oxygen and heat. Some seeds need a little help to germinate, but tomatoes, peppers and eggplant are not among those that need to be refrigerated (a process called stratification which mimics winter) or have their seed coats scratched (scarification) to permit water to enter in order to break dormancy.  

However, if you don’t have a greenhouse and all the timers and heat-producing mats it is still possible to start seeds successfully. Tomatoes and peppers need soil temperature of about 70 degrees or more to germinate, so placing them in a warm spot in the home will work. Placing them near a heater or on the top of a refrigerator where heat from the coils rises and heats the area above it. After germination place in a warm place and provide 12-14 hours of light to keep them from getting leggy when day length is short. A fluorescent fixture with ordinary bulbs can provide the light and should be kept no more than 3 inches from the plant. A south-facing window is good for light too.

I have already assembled my containers, seed starting mix and a good number of seeds of varieties I like to grow. I collect all the half-gallon milk and juice containers through the year and I use about 50 containers because I grow plants for plant sales. I cut out one side of the containers, punch two holes in the side at the bottom for drainage and then fill with seed starting mix. I have had good luck using compost as a seed-starter for several years, but I am open to trying something new this year. The advantage in compost is that additional fertilizing the seedlings is not needed as the compost provides sufficient nutrients until transplanting.

This year I am experimenting with seed starting soil. I am dividing the containers into three groups with each to get a different soil mix: Group 1) compost; Group 2) commercial seed-starter mix; Group 3) 50=50 compost and commercial seed-starter mix. The containers are ideal for labeling with a sharpie the planting mixture used, name of the cultivar and planting date on the backside of the container (what previously was the bottom).

Many directions for seed starting recommend sterile, non-soil starting medium to avoid damping-off fungus, but I have not had a serious problem with damping off. Not overwatering and keeping the planting medium warm with heat seems to keep this fungus at bay.

While I use half-gallon cartons for a lot of my seed starting, I also reuse plastic plant containers from nurseries especially for plants that don’t like to be transplanted such as parsley. I have also used wooden flats for lettuce and other plants that don’t require as much heat to grow.

I start about 8-12 seeds per carton container. After the plants have grown to about 2-4 inches I transplant them to deep 4-6 inch pots to give the roots room to grow which is important to foster better faster growth when transplanted into the garden. After transplanting and the weather warms I put the plants outside where they can get sunlight, grow and get toughened up and ready to transplant to the garden.

If you don’t have time or inclination to grow your own tomatoes, you will have opportunities to buy plants that Master Gardeners and others have grown. The Linden Garden Club holds its annual plant sale on April 4th at Mission Hall in Linden and the Master Gardeners will be having theirs at the Ag Center on April 18th. There will be lots of varieties to check out for a happy summer of tomato, eggplant and pepper tastes as well as herbs and many other plants.

If you have a gardening related question you can contact the UC Master Gardeners at 209-953-6112. More information can be found on our website:    

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Euphorbia euphoria — a fascinating collection of plants

Euphorbias are simply incredible.

Over my many years of visiting various botanical gardens, arboretums, and nurseries, I’ve developed a great fondness for and sense of amazement about this genus of plants. Almost every time our family visits a new public garden, we encounter yet another Euphorbia species, and we exclaim in near disbelief, “That’s a Euphorbia too?!”

Euphorbias are an astonishingly variable and diverse group of plants, with forms that include succulents and spiny, cactus-like species; low-growing groundcovers; leafy, decorative shrubs, some with brilliantly colored, flower-like structures; tall, sculptural trees; and small, pesky, weedy species that I hope never to see in my garden again!

The genus name Euphorbia comes from the ancient Greek physician Euphorbus, who purportedly discovered the plants. The leafy, non-woody forms of Euphorbia are often called “spurges,” a name that derives from the Old French word espurgier and the Latin word expurgare. Both of these words mean “to purge,” since the sap of some Euphorbias was historically used as a laxative or purgative medication.

There are more than 2,100 identified species in the genus Euphorbia. They’re native to locations around the world, occurring naturally on every continent except for Antarctica. Depending on the species, they can be annual (with a lifespan of one year), biennial (with a lifespan of two years), or perennial (living for many years). They can also be evergreen (holding their leaves throughout the year) or deciduous (dropping their leaves seasonally). 

Despite their many differences, Euphorbias do have a few characteristics in common. One is their white, milky sap or latex. In some species this sap is only mildly toxic or irritating, but in other instances it’s poisonous, so it’s always wise to be cautious and wear gloves and eye protection when touching or pruning these plants.

Culturally, Euphorbias all require well-drained soil; many species naturally grow in poor, sandy, or rocky soils. Their water needs are generally low, and most types require plenty of sun exposure and a warm to hot, frost-free climate (although some species are cold hardy).

Plants in the Euphorbia genus also have unique flowering structures called cyathia. Each cyathium is composed of a cluster of tiny, true, male and female flowers surrounded by a cup of fused bracts (modified leaves). In some species, a whorl of larger, colorful, petal-like bracts appears below the cyathia.

The poinsettia (Euphorbia pulcherrima) — described in detail in last week’s article — is probably the best-known species in the Euphorbia genus. Another Euphorbia commonly seen in our area is spotted spurge (Euphorbia maculata), a tenacious, self-sowing, low-growing, readily spreading weed. You can learn more about this garden pest on the UC IPM website.

Besides a table-top poinsettia, my personal Euphorbia collection includes these indoor and outdoor plants:

African Milk Tree (Euphorbia trigona). This was the plant that first introduced me to Euphorbias, since I inherited a potted specimen from my paternal grandmother many years ago. It has three-sided, rigid, succulent green stems adorned with short spines and small ovoid leaves, and it has slowly branched and grown upright to nearly six feet tall. I now also have a more colorful cultivar named ‘Rubra’, which has very pretty, red-tinged stems and leaves.

A close-up photo of the red-tinged stems and leaves of Euphorbia trigona ‘Rubra’
(Photo by Kathy Ikeda)

Ascot Rainbow Spurge (Euphorbia x martinii ‘Ascot Rainbow’). This small perennial shrub has narrow, variegated leaves of blue-green and creamy yellow that emerge in all directions from long, thin, fleshy stems. Its leaves develop a glowing blush of rosy pink in colder temperatures. These plants bloom in early summer to fall, with large sprays of bright yellow-green cyathia that grow from the top of each stem.

Euphorbia Inconstantia (E. inconstantia). This is a cactus-like species that grows in a compact clump of thick, columnar, succulent, bluish-green stems. Its upright growth reaches a height of one to two feet, and the stems are deeply ribbed, with an array of sturdy grey spines emerging along the outer edge of each rib. 

A couple other noteworthy Euphorbia species are:

Pencil Cactus, Pencil Bush, or Milk Bush (Euphorbia tirucalli). This plant is spineless and isn’t a true cactus, but it does have toxic sap containing terpenes and other corrosive chemical compounds (giving it the name of “Petroleum Plant” in some countries). The species plant has bright green, thin, many-branched, vertical succulent stems that reach a height of 2 feet or more. The named cultivar ‘Sticks on Fire’ has stems that transition from bright green at the base to pink and vivid coral red at the ends. It’s a gorgeous accent plant, especially when paired with a succulent having blue-green leaves.

Crown of Thorns (Euphorbia milii). This native of Madagascar has one of the showiest flowering displays of any Euphorbia. Its woody grayish-brown stems are covered with long sharp spines, but each stem is topped with large, rich green leaves and a tight cluster of flower-like cyathia that resemble single begonias. Depending on the variety, the bracts can be pale to bright pink, intense red, creamy yellow, or variegated in color.

Euphorbia myrsinites, another noteworthy species
(Photo by Kathy Ikeda)

For more history, pictures, and descriptions of the different species of Euphorbias, consult these sources:

For gardening-related questions, call the UC Master Gardener office at 209-953-6112, or visit our website.

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Poinsettias: history, fun facts, and more

Poinsettias have become a symbolic plant during the holiday season, their deep green leaves and bright red rosettes adorning tables and windows across the country. Marcy Sousa’s recent column briefly discussed the care of this and other ubiquitous Christmastime houseplants, but let’s take a closer look at this unique plant species.

Poinsettias (Euphorbia pulcherrima) are evergreen to semi-evergreen, perennial plants with woody stems. They’re native to tropical, mid-elevation regions and dry interior forests of central Mexico, where they grow as shrubs or small trees. In their natural habitat, they have open, “leggy” growth and can reach a surprisingly large size, reaching 10 to 15 feet tall and six or more feet wide. 

Brilliant red poinsettias growing in a greenhouse (Photo by Kathy Ikeda)

We enjoy poinsettias for their showy winter display of large, deep green leaves and bright red rosettes. But the vividly colored structures that are commonly thought of as flower petals are actually modified leaves called bracts, and not part of the flower at all. The true flowers are the tiny, yellow-petaled, inconspicuous structures found in a tight cluster surrounded by the bracts. 

If you’ve ever pruned a stem or broken off a piece of this plant, you’ll know that it has a thick, white, milky sap that oozes from damaged or cut surfaces. This sap sometimes causes skin irritation, but it isn’t poisonous, and if ingested it usually doesn’t result in anything worse than mild stomach upset or nausea. (The leaves taste awful.) This milky sap is typical of most plants in the Euphorbiaceae or Spurge family, to which the poinsettia belongs.

People of Mexico’s early Aztec culture prized these colorful plants, and cultivated them to produce a medicinal compound and a reddish-purple fabric dye. In the Aztec language of Nahuatl, the plant was named Cuitlaxochitl (from “cuitlatl”  for residue or soil and “xochitl” for flower). Poinsettias didn’t become associated with Christmas until the 16th or 17th century, when Franciscan priests near present-day Mexico City began to use them in nativity processions.

Joel Roberts Poinsett, a botanist and physician from South Carolina, introduced the plant to the United States in 1825 while he was serving as the first U.S. ambassador to Mexico; the plant’s common name in English-speaking countries is derived from his surname. He died on December 12, 1851, a day now commemorated as Poinsettia Day. 

A German immigrant family by the name of Ecke was instrumental in creating America’s commercial poinsettia industry over 100 years ago. The Eckes became the dominant force in breeding, growing, and establishing the popularity of the poinsettia in the United States, and the Paul Ecke Ranch in San Diego County, California now grows more than 70 percent of poinsettias sold in America each year. The Eckes and other breeders have developed numerous named cultivars of this plant over the years, including plants with atypical bract colors (such as white, yellow, pink, burgundy, and salmon), different bract patterning (speckled, bicolor, and multihued), and double-bracted and miniature forms.

In the last two centuries, the poinsettia has been elevated from a little-known exotic plant to one of the most important and commercially valuable plants in the U.S. floriculture industry. With annual wholesale sales of roughly $60 million—occurring mostly in the six-week period before Christmas—and a contribution of more than $250 million to America’s retail economy, the poinsettia far outpaces the sales of its closest competitor, the orchids. 

Like many plants, poinsettias are photoperiodic, meaning that their growth cycle responds to the seasonally changing length of light and dark periods during a day. However, poinsettias are also in a smaller group known as “short-day” plants, meaning that they naturally flower in the winter and they need to have less than 12 hours of light per day (and nearly total darkness for the rest of the day) in order to begin the bloom cycle. Most poinsettias develop their full color from 8 to 9 weeks after the flowering cycle is initiated, depending on the variety. Once full color is reached, plenty of light is needed to maintain the bright hues.

A poinsettia plant just beginning to develop color in its upper bracts. (Photo by Kathy Ikeda)

Commercial growers use a very specific and carefully timed regimen of pruning, fertilization, pest management, and controlled exposure to artificial light in order to develop the uniform looking, cheerful plants we see in stores and nurseries every year. New poinsettia plants are generally grown by taking cuttings from the stem ends of mature plants, but many cultivars are patented and they shouldn’t be propagated by anyone other than the patent holder.

Poinsettias prefer soil on the dry side and don’t like “wet feet” or soggy soil. They’re also easily stressed by lack of sufficient water, and will drop leaves and bracts readily if the soil is too dry. Monitor the soil moisture of potted plants carefully to keep them in good health. 

Poinsettias are usually treated as throwaway plants, discarded in the trash after the holidays. However, with proper care and attention, they can be maintained as houseplants for repeat performance of bloom. In some areas, they can also be planted in the garden. 

According to the Sunset Western Garden Book, poinsettias aren’t suitable for outdoor planting in our climate zone because we get below-freezing temperatures each winter. However, they could be grown successfully as outdoor potted plants if the pots are placed in a sunny location and are moved to a warm, protected area during the colder months of the year.  The garden guide’s growing instructions include these tips: “Thin branches in summer to produce larger bracts; or prune them back at 2-month intervals for bushy growth and smaller bracts. To improve red color, feed every 2 weeks with high-nitrogen fertilizer, starting when color begins to show.”

Enjoy the cheerful colors of poinsettias while they last, and if you want to try a fun experiment, try growing your 2019 plants as a “Happy New Year” project during 2020!

For gardening-related questions, call the UC Master Gardener office at 209-953-6112, or visit our website:

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