An up-close look at pollen (achoo!)

For many people, pollen is the “p-word”. . . as in, “PLEASE, don’t say that word!” The mere mention of pollen can conjure up runny noses, watery and itchy eyes, and looks of desperation from those with hay fever. Here in the fertile, crop-rich San Joaquin Valley, it’s often said that if you don’t already have allergies, you’ll develop them.

Trees such as oaks, birches, conifers (pines, firs, spruces), and nut crops (walnuts, almonds, pecans) are especially prolific producers of pollen, and they’re ubiquitous in our area. They’re joined by other common pollen-producing plants, including grasses and many of our favorite garden flowers. It’s an allergy sufferer’s nightmare.

Pollen literally means “fine flour” or “mill dust” in Latin. While it’s a health nuisance, it’s also a valuable and necessary evil.

We’re familiar with pollen as that yellowish, powdery-looking stuff that drifts away from trees and other plants in spring and summer, making us miserable as it floats through the air, collects on our cars and homes, and settles in our nostrils. But without pollen, we literally couldn’t survive. The vast majority of plants on Earth depend on pollen for their reproduction, and we in turn depend on plants for food and oxygen.

Pollen is unique to seed-producing plants, which are divided into the flowering plants (Angiosperms) and the cone-bearing plants (Gymnosperms). The pollen-bearing structures of these plants are contained either in the flowers or the cones. More primitive plants such as ferns, fungi, mosses, and horsetails don’t make pollen; instead, they produce spores.

So, what exactly is pollen, anyway?

A clue to pollen’s specific purpose lies in the aforementioned scientific classifications of pollen-producing plants: the suffix –sperm means “seed” in Greek. Pollen is the male vehicle for a seed-forming plant’s sexual reproduction. Each microscopic pollen grain has a hard outer coating that protects the inner contents—two sperm cells and a tube cell—from damage and dehydration.

Plants fall into two categories when it comes to the type of pollination: (1) self-pollinated, or (2) cross-pollinated, where pollen from one plant must transfer to another plant of the same species.

Pollination begins when grains of pollen move from the male part of a plant to the female part of a plant. Pollen transfer can occur in one of two ways: (1) abiotic pollination, where pollen is carried by wind or water (most common in grasses and trees), or (2) the far-more-typical biotic pollination, where a living organism such as a bee, butterfly, moth, wasp, fly, bird, bat, or other animal moves the pollen (most common in non-tree flowering plants).

Once a pollen grain comes in contact with the female part of a plant, it germinates. A pollen tube develops, emerging through a specialized opening in the outer covering then extending toward the structure that holds the egg. The sperm cells then leave the pollen grain and travel through the pollen tube, ending their journey when they reach the egg. Fertilization occurs once the plant’s egg/ovule and sperm cells unite, and that initiates seed development.

Some amazing pollen-related facts about corn: Just one stalk can produce about 18 million pollen grains! The pollen grains land on the ends of the female corn silk; there is one strand of silk attached to each developing kernel. The single-celled pollen tubes that grow from the pollen grains through the silk can be up to a foot long!

Many small members of the animal kingdom depend upon pollen. Honeybees and native bees use protein-rich pollen, either eating it themselves or mixing it with sugary nectar before feeding it to their developing larvae. (Pollen is not used to make honey; honey is regurgitated nectar.) Some beetles—including ladybugs—and many common types of web-weaving spiders also consume pollen as part of their diet.

When seen under a microscope, pollen grains are exquisitely beautiful natural works of art. Their outer coatings are intricately patterned, spiked, or pitted, and different plant species produce their own unique pollen designs. Pollen can be sticky-surfaced or spine-studded so that it’s easily carried on the hair, feathers, or fur of pollinators, or it can be lightweight and aerodynamically crafted to float in a breeze.

False-color scanning electron microscope image of pollen grains from a variety of common plants: sunflower, morning glory, prairie hollyhock, oriental lily, evening primrose and castor bean. (Public domain image from the Dartmouth Electron Microscope Facility)















For more information and a visual treat, read the book Pollen: The Hidden Sexuality of Flowers, or search the Internet for “pollen electron microscopy” to see extraordinary images. And try very hard to appreciate pollen, even as it makes you sneeze.

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


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The Fun and Fascinating Ladybug

Let’s take some time to learn more about one of our much-adored garden inhabitants: the lady beetle or ladybird beetle, commonly referred to as the ladybug.

The name “lady beetle” originated during the Middle Ages, when Catholic farmers prayed for relief from crop-destroying insects. When small beetles arrived and began devouring the pests, it was thought to be an act of the Virgin Mary, and the rescuers were named “Beetles of Our Lady.” The rest is history!

Entomologically speaking, the ladybug isn’t a true bug (those insects belonging to the order Hemiptera). Instead, it’s a member of the order Coleoptera, which means “sheath winged” and includes beetles and weevils. Most Coleopterans are helpful hunters of harmful insects. The specific family to which ladybugs belong is Coccinellidae.

Amazingly, there are nearly 200 species of ladybugs in California. One of the most common in our area and throughout North America is the Convergent Lady Beetle (Hippodamia convergens). The adults of this species have two elytra—the pair of modified wings that forms a hard cover—that are red with black spots; their heads, legs, and antennae are also black in color.

Different ladybug species can vary greatly in appearance. Some ladybugs have orange, yellow, grey, brown, or even black elytra; some have numerous spots, while others are spotless. The common names of ladybugs often reflect the number of spots on their shiny backs: seven-spotted ladybug, twelve-spotted ladybug, and so on. Other names are more interesting. One example is Chilocorus orbus, a native California ladybug with two large red spots on its jet-black elytra; its rather frightening common name is Twice-Stabbed Lady Beetle.

Like butterflies and moths, ladybugs undergo complete metamorphosis, passing through four different life stages: egg, larva, pupa, and adult.

During the spring and summer, a female ladybug lays small clusters of oblong, yellowish-colored eggs. She deposits them near aphid colonies or other pests, so that her “babies” will have a handy source of food when they emerge. A single female can lay up to 1,000 eggs in a single season. The eggs hatch into larvae in about three to five days.

Ladybug larvae are small but fearsome looking, and it’s important to recognize them so as not to squash them in a moment of panic or revulsion! They are usually about 1/4 to 3/8 of an inch long, dark brown to black in color, with bright spots or bands on their bumpy or spiny exoskeletons.

Larval ladybugs are efficient and highly mobile hunters, and they’re more effective predators than adult ladybugs. They use their large mandibles (chewing mouthparts) to feed upon aphids, mealybugs, scale insects, mites, leafhoppers, and other soft-bodied insects. A single larva can consume hundreds to thousands of insects from the time it hatches until it begins to pupate. Once the pupa forms, it takes several days to two weeks before an adult ladybug emerges.

Larva of the Convergent Lady Beetle eating an aphid (Photo by Jack Kelly Clark, UC IPM)

Pupal form of the Convergent Lady Beetle (Photo by Jack Kelly Clark, UC IPM)










It can be tempting to buy a squirming bagful of ladybugs to release at home. It’s certainly entertaining to watch the little critters crawl away, looking like miniature hemispherical hovercrafts. But before you purchase ladybugs, consider these potential pitfalls:

  • Ladybugs should be released in the evening in a location with moisture and plenty of their favorite prey. Without these conditions, they usually fly away.
  • Commercial vendors often collect ladybugs from the wild, while they’re congregating and relatively inactive during the winter. Removing them can negatively affect the ecological balance of an area.
  • Non-native ladybugs can be introduced to areas where they displace native species and become pests themselves. Be careful to purchase local ladybug species.

Rather than buying ladybugs, try attracting them to your garden by creating a welcoming habitat. Adult ladybugs eat nectar and pollen in addition to insects, and they also need places for shelter. Composite flowers (asters, coneflowers, sunflowers, and yarrow) and other flowering plants such as alyssum, penstemon, and milkweed are ladybug favorites, as are edible herbs such as chives, cilantro, and dill. Large grass species, including native deer grass, provide excellent shelter for overwintering congregations of ladybugs.

Convergent Lady Beetles congregating at the U.C. Berkeley Botanical Garden (Photo by Kathy Ikeda)













If you’re fortunate, you might find ladybug eggs, larvae, or pupae in your own yard this summer, and be able to witness another part of this amazing insect’s life cycle.

For a good layperson-friendly guide to ladybugs, check out the “Identifying Ladybugs” page on the website of the Natural History Museum of Los Angeles.

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

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Tune In To Radio Show For Great Garden Tips


"Farmer Fred" hosts two radio programs on Sunday mornings, offering advice on growing healthy gardens that resist pests and reduce chemical use.

Finding garden advice is easy, but scientific research has raised awareness of our impact on the environment, challenging many traditional practices. Accessing and interpreting this information can be difficult; one place to go is the airwaves, where you can listen to California native and long-time gardener Fred Hoffman, known to many as radio personality “Farmer Fred”.

Fred uses a blend of humor and hands-on experience to share his message of earth-friendly gardening practices. His journey began 37 years ago with a dangerous chemical, which is both ironic and more common than you might think. Fred’s dog at the time had fleas, so he covered the backyard with Diazinon, a highly toxic insecticide for household and garden pests (it was made illegal for residential use in 2004). It worked a little too well; the usual buzzing drone of backyard life was soon replaced by an eerie silence, telling of the insect community’s wholesale destruction. This was Fred’s “aha” moment, which so many organic gardeners have after such an experience, when one decides there must be a better way.

You may not like those creepy-crawlies, but annihilating insect communities only causes more problems in the long term. Fred’s determination to find a better way led him to the newly minted University of  California Master Gardener program, where trained volunteers bring research-based knowledge to home gardeners. Fred became a certified Master Gardener in 1981, and has since logged over 8,000 volunteer hours, harnessing his training and a lifetime of personal experience to educate the community about better ways to manage pests.

Fred’s gardening know-how and quirky personality appear on “The KFBK Garden Show”, and “Get Growing With Farmer Fred”, both airing out of Sacramento on Sunday mornings. Fred loves to talk about tomatoes, but like any good talk show host, he covers a wide array of topics: vegetables, fruit trees, roses, ornamentals, succulents (e.g. cactus), irrigation, lawn care, etc. His message is always underscored by one of his favorite mottos: “surf with Mother Nature”. This means favoring plants appropriate for our climate, encouraging a balanced insect community, building healthy soil, and taking other actions to work with, rather than against nature.

Each week Fred invites a guest on to the show to share their expertise. Some are regulars, such as American River College horticulture instructor Debbie Flowers, and soil specialist and organic gardening advocate Steve Zien. Other guests include nursery owners with decades of experience, garden writers, Master Food Preservers (an off-shoot of the MG program), rosarians (rose experts), and people involved in “plant trials” conducted by the University of California, who share the latest in growing beautiful, water-wise plants.

Some of the gardening practices Fred talks about have been around for decades (or centuries), but there is always more to learn. Fred has an announcement segment where he shares information sent to him from various organizations offering classes, workshops, conferences, plant sales, home and garden shows, and other educational or just-for-fun events.

Another important service Fred’s show provides is announcing serious pest threats in the area, and what you can do to help slow the spread. Sometimes it’s as simple as eliminating standing water where mosquitoes might lay their eggs; other times, there are more serious steps such as contacting the Agriculture Commissioner if you spot Asian Citrus Psyllid on your citrus trees. Fred also covers quarantines, which is hardly everyone’s favorite topic, but are important in the protection of the area’s agricultural economy.

Fred has two great websites, one being a supplement to the “Get Growing” radio show (see below), the other a blog entitled “The Farmer Fred Rant®”. Both have great gardening tips for Central Valley residents wishing to improve the health of their garden and the environment. In spite of the blog’s name, there isn’t any real “ranting” going on, just a sprinkle of sass here and there to keep things interesting.

Fred’s two radio shows air back-to-back on Sundays: “The KFBK Garden Show” begins at 8:00am on 93.1FM KFBK, followed by “Get Growing With Farmer Fred”  from 10:00am-12:00pm on 650AM KSTE. For the farmers out there, he also hosts “The KSTE Farm Hour” at 12pm after “Get Growing”. Links to his blog and podcasts can be found at

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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Managing Leaffooted Plant Bugs in Your Garden

The Western Leaffooted Plant Bug is a pest of many plants, such as citrus, tomatoes, and pomegranates.

The garden’s bounty is in full swing, offering humans and insect pests a full buffet of goodies to munch on. One such pest of the Leaffooted Plant Bug (LPB), an insect related to the stink bug and lover of both edible and ornamental garden plants. While most veggies and fruit can handle light feeding by the LPB, letting populations get out of control may cause more serious problems.

LPBs are relatively easy to spot. Of the three species commonly found in California gardens, the Western LPB (Leptoglossus zonatus), with its brown, 1-inch long body and white zigzag-patterned back is what you will most likely find amongst your edibles (see photo). The distinguishing feature and namesake of all LPBs are leaf-like enlargements on the hind legs of adults, which serve as weapons in what can best be described as “thumb war” with legs. Females and males use their leafy legs in territorial disputes by waggling threats at each other and delivering beatings. Males attempt to dislodge opponents with a single-legged hook over the thorax, or a double-legged squeeze to the abdomen.

This predilection for knocking each other about does not preclude them from forming aggregations of 5-500 individuals on leaves, stems, and fruits. Adults spend the colder winter months snuggled up in protected areas of the garden. Woodpiles, barns, palm fronds, citrus or juniper trees, tree cracks, and pump house shelters all serve as winter vacation homes. Feeding and mating commence in spring, with their cylindrical, brown eggs laid end-to-end on leaves and stems, hatching into reddish-brown nymphs in about a week. All three stages (egg, nymph, adult) can exist at the same time during the growing season, with females laying an average of 335 eggs in their lifetime.

The Leaffooted Plant Bug feeds by piercing fruits and other plant parts with their long proboscis, sucking the juices out. They are partial to pomegranates, tomatoes, and citrus, but will attack almost anything. Nymphs have short probosces, causing superficial damage only; adults have much longer probosces, getting down to the seeds and excreting an enzyme to liquefy them for easier digestion. Adults feeding on small-sized fruits such as immature tomatoes may cause them to abort. Feeding on larger-sized fruits such as citrus or mature tomatoes may cause surface depressions, discoloration, and reduced “juiciness”. Damage to mature fruits is usually only aesthetic, and will not cause serious problems for the home gardener unless the population is overwhelming your plants. Ornamentals are also subject to LPB feeding, but damage is typically minor, only affecting leaves and stems.

If you have spotted the Leaffooted Plant Bug in your garden, it is best to take care of them when populations are low. The best control method is manual: shake the LPBs out of your plants onto a sheet, dump them into a bucket of soapy water, then dispose of them in your garbage. This technique is most effective under the following conditions: 1) it’s done early in the morning when the adult LPBs are still sluggish and less likely to fly away, 2) the population consists of more (flightless) nymphs than adults, and 3) it is performed on a regular basis, at least 3 times a week to start, until the problem is under control.

Another important management strategy is to reduce their sources of winter food and shelter. Remove as much of their overwintering habitat (see above) as possible; remove or mow down weeds, which supply seeds that feed LPBs in winter and early spring when fruits are unavailable. Applying mulch to the soil surface will help reduce weed populations as well.

Sound like a chore? Unfortunately, the LPB shares the stink bug’s talent for secreting a foul-smelling compound when annoyed, making them undesirable to many potential predators such as birds and other insects. There are a few parasitic wasps and flies that prey on LPBs, and once you get a serious infestation under control, these natural enemies can keep populations in check. Broad-spectrum pesticides can help bring a serious infestation under control if you have mostly nymphs, but this will kill off your pollinators and other beneficials that offer long-term management, so use pesticides only as a last resort. Please note that there are no pesticides available to homeowners for effectively managing adults LPBs.

The UC Division of Agriculture and Natural Resources is researching the Leaffooted Plant Bug’s spread throughout California. You can help by taking a quick, 2-minute survey. Go to their Pests in the Urban Landscape blog at <>. Click on the survey link at the bottom of the June 17th post entitled “Leaffooted Bug” to let them know whether you saw the LPB in your garden and what plants you saw them on. This survey will be up until July 15, 2016.

More information on Leaffooted Plant Bugs can be found on the UC Integrated Pest Management’s website at <>. 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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Gardening tips for tomatoes, squash bugs

Tomato season is here and I have heard this complaint several times from gardeners. “My tomato plants are tall and healthy looking, but I don’t have any tomatoes. What might the problem be?”  Well the problem might be that the gardener used too much nitrogen fertilizer and it stimulated lots of vegetative growth to the detriment of fruit set. Generally tomatoes do not need a lot of nitrogen fertilizer.

Another cause of poor tomato fruit set might be lack of phosphorus which is the important nutrient to stimulate fruit set. This is not likely a problem here as valley soil phosphorus is usually adequate. I use two shovels of compost per plant and they do fine as my soil is a fertile clay-loam as are lots of soils in the County. If you have sandy soils fertilizer such as 5-10-10 may be appropriate. You can also mulch with compost.

Another problem might be lack of sun. Tomatoes need about 6 to 8 hours of sunlight each day to set fruit, otherwise spindly fruitless plants. One other cause of poor fruit set can be temperature.  Fruit set is reduced at temperatures greater than 90° F and is optimal in the day time range of 65-80° F and night time range of  59- 68°F. Fruit set is poor at temperatures less than 55° F. If we have a prolonged period of day temperatures over 90 ºF, expect poorer fruit set during that time.

Insufficient water will also cause blossoms to fall off, so another good practice is regular watering and water deep. Tomato roots will go 4 feet deep. I apply water every 3 days for 90 minutes, about 3 gallon per plant using a drip system on a controller. Inconsistent irrigation can cause a calcium imbalance in the plant which results in blossom end rot and a tomato that you won’t be eating. The problem is the watering and not lack of soil calcium. Most soils have sufficient calcium available for plants. Hence, throwing egg shells or other calcium sources at your tomatoes usually won’t help. Overwatering can also cause cracking and splitting.

One of the things I learned as a Master Gardener was the bees actually increase pollination in tomatoes. This was confusing to me because I know that tomatoes are self-pollinating. Apparently, a bee buzzing the flowers enhances the transfer of pollen within the flower. Giving tomato cages a shake as you pass by enhances pollination for the same reason.  I spend a lot of time in the spring making sure the tomatoes stay within the cages, so I give the cage a little shake   as I pull straying vines back into the cage. Stray vines can also be pruned off as well to keep the plant tidy and inside the cage. For more information on tomato growing see:

Squash bugs (Anasa tristis) are widely distributed in North American and a nasty pest of squash and pumpkins. About 4 years ago I thought I had won the battle. I killed all the overwintering bugs so they did not reproduce. For three years afterward, no squash bugs showed up in my zucchini patch.  However, last year I had a few and this year a great many once again, so somehow they found my isolated garden. I have repeated my ‘kill on sight’ approach and here is how I have managed to keep these pests at bay. It requires daily diligence. Monitor your plants and if you see wilting in the morning, you better look for squash bugs or eggs on the stems or under the leaves. Eggs are laid in lines or clusters and are bronze to red in color and about 1/16 inch long. They hatch in about 5-10 days into small grey nymphs. Scraping off the eggs results in death to the eggs because they have no nurturing substrate when they hatch. You can also use duct tape or masking tape to remove eggs and nymphs. Once they hatch successfully it is far more difficult to catch and kill the small nymphs.

To get the adult bugs, I have found that splashing water on the base of the plants will send the bugs climbing up the stems to safety to avoid water and drowning, but instead, they get a quick death squished between my thumb and forefinger. They don’t smell great, but don’t be squeamish if you want zucchini. Boards or wood shingles placed under the plants will also provide a hiding substrate for attracting and collecting them. Squash bugs can cause wilt ‘anasa wilt’ which is thought to be from toxic substances injected by their sucking mouth parts which also remove sap from the plant. For more info:  and  Happy squash bug squashing.

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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Protecting Plants from Summer Heat

Scorching days have arrived! All but the hardiest of us wilt when outdoor temperatures hit the 90s and 100s, and we seek refuge in air-conditioned places or in water-cooled outdoor areas. Plants don’t have that luxury; they’re literally rooted where they are, and they sometimes need our help to deal with the Central Valley sunlight and heat.

Summer weather can damage plants by stripping them of the moisture they need or by exposing them to more heat or light than they’re adapted to handle. Higher than usual air temperatures, intense light, and overheated or too-dry soil can harm a plant’s leaves, stems, and roots. Wind can further worsen the effects of hot air.

Like humans, plants rely on water partly to cool themselves: we sweat, plants “transpire.” Transpiration is the process by which plants absorb water through their roots, move this water upward through the part of their vascular system called xylem, then lose this water through tiny pores called stomata on the leaf surfaces. The transpiration rate rises in hot temperatures; a plant’s water loss generally doubles with every 18-degree increase.

Plant species vary in the amount of water they need to resist heat and maintain good health (hence their classification as low, medium, or high water use). New plant growth, tender seedlings, fruits and vegetables, and cool-season annuals are particularly susceptible to sun-related damage.

Plants exhibit different levels of heat damage, and it’s important to know the distinction. Wilting is the drooping or shriveling of plant tissues that occurs when they lack sufficient water; it’s reversible if plants are watered in time. (Large-leaved plants will usually wilt a little during peak daytime heat even with adequate water, but will recover when temperatures cool.) Heat stress is when plants begin to suffer irreversible heat-related damage; at this stage, some plants will try to conserve water by dropping leaves or buds. Sunburn (or “leaf scorch”) is when a plant’s leaves or non-woody parts are permanently and severely harmed by excessive heat or sunlight; leaves develop dried brown patches or margins and they eventually wither and fall off. Sunscald is the cracking, discoloration, and warping of bark that occurs when the trunk or branches of a woody plant get too much sun exposure; the damage is permanent and very harmful since it increases the plant’s disease susceptibility.

Follow these simple guidelines to minimize heat damage:

  • Conserve soil moisture and protect plant roots from excessive heat by covering bare ground with a 2- to 4-inch-thick layer of organic mulch—wood chips, shredded bark, leaves.
  • Don’t place inorganic mulches—sand, pebbles, rocks, shredded rubber—or black-tinted mulch near plants in sunny locations (with the exception of desert-adapted plants), because these materials collect and radiate heat.
  • Follow the principle of “right plant, right place.” Select plants adapted to our Mediterranean climate and choose planting locations with proper exposure. (No shade-loving plants in full sun!)
  • Don’t heavily prune trees and shrubs in summer, because this can suddenly expose tender bark to the sun’s intense rays. It also encourages a flush of heat-sensitive new growth and places additional energy and water demands upon heat-stressed plants.
  • Avoid planting during peak summer heat; this stresses plants and compromises their chances of successful establishment. Delay planting until fall, or (if you must plant this season) wait until a cooler spell, plant in the evening, and water deeply after planting.
  • Keep potted plants well watered and (if possible) move them to shadier locations. Use light-colored or plastic containers, which absorb and transmit less heat than dark-colored containers or those made of ceramic, cement, or metal. Hydrogels (water-retaining polymer granules) can be mixed into potting soil to help hold moisture.
  • Whitewash trunks of young trees to help prevent sunscald. Mix equal parts water and white interior latex paint, then apply it from 1 inch below ground to at least 2 feet above ground.
  • Use strategically placed shade cloth to shelter plants.
  • Ensure that plants receive appropriate and consistent levels of water, and check irrigation systems for proper operation. Do this yourself, or enlist the services of a Qualified Water Efficient Landscaper (

Just in case you’re wondering, it’s a myth that water droplets act as miniature magnifying glasses and burn leaves. Overhead watering generally should be avoided for water conservation and disease prevention purposes. . . but sometimes wilting plants (like us!) appreciate a cool sprinkling on a hot summer day.

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

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Nectar Guides: How Bees Find Food

Bees see the world differently than humans. The top image shows Black-Eyed Susans as we see them, the bottom as bees see them

Humans love flowers because of their beautiful colors, intriguing shapes, or lovely fragrance. From the plant’s perspective, however, these qualities are more about function than aesthetics. Plants dependent upon pollinators such as bees must make themselves attractive; insects dependent upon plants for nectar or pollen must be attracted to their source.

This last point seems obvious. How could a bee not see a flower? They can, of course, see flowers, though not in the same way humans do. Bees have a total of five eyes: three ocelli, simple eyes located on top of the head, and two large compound eyes, located at either side of the head. The compound eyes have thousands of lenses each, and create a world of movement and light, rather than distinct shapes and outlines.

One amazing thing these eyes do is allow bees to see ultra-violet light, which is invisible to humans. This is important for pollinators because many flowers have “nectar guides”, meaning patterns or markings on the flower that guide bees to a reward of nectar, pollen, or both. Some flowers have nectar guides that are visible to humans, such as Foxglove or Alstroemeria, while other flowers that appear to be a single color reveal their nectar guides only under UV light. One example is Black-Eyed Susan, pictured above. The chemical compounds responsible for these patterns, flavonols, also absorb UV light, protecting the delicate reproductive parts of the flower from harmful mutations that might render a plant sterile.

Bees can see nectar guides from a distance, but these markings are less about attracting pollinators from far away than about telling them what to do when they arrive. The distinctive patterns, which can take the form of spots, streaks, or “bull’s eyes”, make pollinating activities more efficient. Pollinators can move quickly from flower to flower, making it more likely they will return to that same species if they have learned how to forage on it effectively. Studies have shown that nectar guides decrease the amount of time a pollinator spends per flower, which allows them to pollinate more flowers total, a bonus for plant and pollinator.

Nectar guides are also good for discouraging certain behavior, namely nectar robbing, which is when a pollinator takes food from a flower without “paying” for it. For example, if our native Valley Carpenter Bee cuts into the base of a flower and sips out the nectar without touching the reproductive organs, the flower won’t be pollinated. Since guides are generally on the inside of the flower, bees will tend to go in that direction first if they can fit inside the flower (Carpenter Bees are too big, so nectar robbing is their only choice for many flowers they encounter). Keep in mind that although nectar robbing is common, it doesn’t necessarily prevent pollination. Some theorize that flowers may be pollinated in spite of the bee not being directly inside the flower; “legitimate” pollinators are also forced further away to find another patch of flowers, preventing inbreeding of plants.

Not all plants have distinct nectar guides. Scent is another option for attracting pollinators; bees have a very strong sense of smell, 100 times stronger than us! Experiments have shown that bumblebees can carry the scent of anise (fennel) flowers back to their colony, and release it, along with their own pheromones, to give their sisters a clue about what to look for (they don’t necessarily do dances, like honeybees, to indicate where exactly the food source is).

Pollinators and plants make a good team, forming a mutually beneficial relationship in which each provides an essential service to the other. Nectar guides are integral to this relationship, an ingenious method for getting food to the bees and bees to the food. This process may be only partly visible to humans, but happy, well-fed bees can only be good news for us!

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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Caring For Your New Water-Wise Garden

Mulch conserves water and adds a finished look

This past summer, the California Department of Water Resources began offering rebates to San Joaquin County residents for replacing existing turf with edibles or ornamental water-wise perennials. These programs, along with a growing sense of ecological responsibility, have inspired many to move into a different genre of plants, leaving behind the familiar Hydrangeas and Bermuda Grass. If your garden has become a “terra incognita” of Deer Grass, Foothill Penstemon, and Texas Ranger, the absence of experience may cause you to revert to familiar watering, pruning, and fertilizing regimens. However, your new landscape may require a new mindset and different cultural practices to keep it healthy and beautiful.

Before you do anything else, get up close and personal with your plants. Determine each plant’s natural cycle throughout the year: Will it drop its leaves in winter? In summer? When does it bloom? Does it like full sun or part shade? Does it tolerate heavy soil? The learning curve is always high for newbies; this is normal, as is the “editing” a new garden receives to determine which plants are best suited to the quirks of your garden conditions.

Besides considering the conditions a plant needs to be happy, there are other aspects of water-wise gardening to think about:

Irrigation is one of the trickiest elements in any landscape, and a new water-wise garden may require you to rethink how you apply water. Many traditional landscape plants are thirsty in our climate, allowing a lot of fudge room for excess water. Low-water plants are not always as forgiving, as they are native to regions with little to no rain during the summer. Most will need some supplemental water, just not several times a week like your lawn did.

How much and how often to irrigate depends on many factors, including plant species, soil type, weather, and much more. Some basic principles include providing water to the entire root zone, and preferably just beyond, encouraging roots to grow outward. Extra water is necessary during the first 1-2 growing seasons to develop a healthy root system, which is essential for future drought tolerance.
See Yerba Buena Nursery’s webpage on plant establishment for more tips:

Mulch is essential to water-wise gardening. All mulches help retain soil moisture, though other benefits depend on the material. Organic mulches such as bark chips are best for most situations, providing organic matter, which improves soil structure. Succulent plants prefer gravel.

Getting the thickness of the mulch right is important as well. Thin layers provide no benefits, whereas thick layers can prevent rain water and oxygen from reaching the soil. Large bark chips (2” or more across) have a naturally porous structure, so a 3”-4” layer is good. Smaller chips and shredded materials are dense, so 2”-3” is about as thick as you want to go.
More information on mulching can be found at:

Pruning is a big topic. However, understanding your plants’ life cycles can tell you a lot about how to prune. Some pruning guidelines will be familiar: herbaceous perennials need to be cut to the ground; winter-deciduous species can be pruned during their dormant period. I recommend pruning water-wise evergreens (plants that retain leaves all year) after they flower, allowing time for pruning wounds to heal before the rains come to prevent stem rot.

Water-wise plants typically despise the shearing we foist upon traditional landscape plants such as Indian Hawthorn and Boxwood, which are better adapted to the excess irrigation necessary for this practice.

Fertilize your water-wise plants only if there is a severe deficiency in the soil. Plants that evolved in lean soils should grow at a moderate pace, so look for fertilizers with low analysis to avoid rapid, weak growth that attracts pests and shortens the plant’s life-span.
For help in reading fertilizer labels see the following website:

More tips on water-wise gardening can be found at
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 at


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Keeping weeds under control

Last week I wrote about some of the weeds and invasive plants I have had to deal with. This week I will present some ways of dealing with weeds in your gardens. One of the most important ways to deal with weeds is to keep them from going to seed. Weeds produce lots of seeds per plant, often thousands to over 2 million in the case of purslane, a common garden weed. Unfortunately, land that has been left to the weeds like my vegetable garden was before I started gardening, builds up a weed seed bank in the soil.

These seeds remain dormant until changes in temperature, light, oxygen, moisture or other factors induce the seed to break dormancy and germinate when conditions are favorable for their survival. Hence seeds deep in the soil, with no light and perhaps no oxygen, remain dormant. However, with tillage to bring them to the surface they germinate.

Seeds on the soil surface typically have a much shorter lifespan than deeply buried seeds, because they are exposed to many organisms and processes that cause their death which include rodents, insects, soil-borne pathogens, UV radiation and other mechanisms. Deeply buried seeds of some weeds may remain dormant and viable for up to 60 years.

Another approach to control weeds in the garden and landscape is to irrigate to germinate their seeds and then remove them by a shallow cultivation. Doing this two of three times in the spring will greatly reduce weed abundance.

An approach which works in sunny gardens is to solarize the soil in July and August. The soil is thoroughly irrigated and UV resistant clear plastic is laid over the damp soil and sealed at the edges for 4-6 weeks to increase soil temperatures to about 140 ºF. This will kill nematodes, pathogens and weed seeds down to a depth of about 6 inches. Solarization will kill the seeds of some perennials like bindweed, but not their roots and rhizomes. Afterwards the soil should not be tilled deeply or new seeds from the weed seed bank will be brought up to germinate. Vegetables definitely thrive better after solarization as there are fewer pathogens and it enhances the breakdown of organic material to provide plant nutrients.

In the landscape, shade is the enemy of weeds so shrubs, groundcovers, and mulch will usually keep weeds at bay. Mulching to a depth of 3 inches not only saves weeding but conserves water as well. I am not a fan of landscape fabric having found it harmful to my rose garden’s health, but when I landscaped my wife’s studio, it was a necessary evil to keep bindweed at bay.

Bindweed (Convolvulus arvensis) is a perennial weed which reproduces by seeds, but once established comes back to haunt us every spring making it difficult to deal with. Bindweed is a Eurasian native that first invaded San Diego County in 1884. It has since become established throughout California below 5000 ft. It was declared the worse weed in the West in the first quarter of the 20th century. Roots can go 14 feet deep and roots and rhizomes from one plant may have many shoots above ground. For more information on dealing with this weed see:

Nutsedge can be controlled by diligently removing young plants before tubers are formed

Another perennial that is hard to deal with is yellow nutsedge (Cyperus esculentus). It produces   tubers on underground stems (rhizomes) that grow as deep as 8 to 14 inches below the soil surface. Most tubers occur in the top 6 inches and these tubers can form new plants. If tubers are not retained when dug out with the plant, buds on the tubers sprout and grow to form new plants.

Tubers rather than seeds are the main source of new plants. Removing young plants with 5 to 6 leaves before they develop tubers is a smart way of eliminating this weed. This requires a lot of diligence and persistence. It can be a problem in lawns and landscapes as well. Nutsedges will emerge through bark or rock mulches and I have seen them penetrate landscape fabric as well. For more information on nutsedges see:

As a last resort there are some herbicides which may help control weeds in some places and circumstances, but not in food growing areas or around roses or other ornamentals that are highly sensitive to some herbicides. Glyphosate has been listed as probably causing cancer by the World Health Organization, so use with caution. More information on weed control and benign herbicides can be found here:

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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Weeds and invaders-the gardener’s nemesis

It was a fairly wet winter here with 16 inches of rain so far. Consequently, weeds have done well and I am fighting hard to get things under control. Common Mallow (Malva neglecta), Redstem filaree (Erodium circutarium), barley foxtail (Hordeum jubatum) which also could be named the veterinarian’s mortgage lifter, field bindweed (Convolvulus arvensis), scarlet pimpernel (Anagallis arvensis) and yellow nutsedge (Cyperus esculentus) seem to be everywhere and my garden in particular shows inadequate weeding.

My mother’s definition of a weed still works for me. A weed is a plant you don’t want. It is a plant in the wrong place. It could be a rose in your corn patch or a corn stalk in your roses, but if you don’t want it there—it is a weed. But the agriculturist’s definition is: a valueless plant growing wild, especially one that grows on cultivated ground to the exclusion or injury of the desired crop. That definition can work for gardeners too.

A good example is the violets which I love in my lawn and landscape but not in my strawberry patch. I have one old strawberry row that I had intended to rototill under, but I never got around to it and now it is invaded by violets. Strawberries are present now so rototilling will need to wait until I am done eating them.

I have played ‘whack a mole’ with weeds for years it seems. I have dug out nutsedge roots and tubers and have come to agree with the adage that the only way to get it out of your life is to sell the farm, but, unless you move to an apartment, it will likely be at your next place too. Alkali mallow or Sida Mallow (Malvella leprosa or Sida hederacea, depending on your favored taxonomist) is another persistent perennial weed that comes back each year though I cut it off each time it comes up, I cannot kill it because it has deep roots that I suspect are all from one underground root system as is the case with bindweed.

At one of our Master Gardener training sessions on weeds, the instructor informed us that he controlled bindweed by whacking it every time it reared its face and after 2 years eliminated it by starving the root.  Hence, I have tried that approach, but my problem seems to be a garden much larger than the instructor’s.

In the turf areas I pretty much tolerate all manner of plants with the one exception of dandelions. They are fine except for the fact they bloom fast and release seeds that soon become more ‘bloomin’ dandelions. Being perennial, they come back year after year to bloom again. Another ‘whack a mole’ plant to deal with.

In my landscape I have some plants that have naturalized and are impossible to eradicate.  One is Bermuda buttercup (Oxalis pes-caprae) which is a South African bulb now common to inland and coastal landscapes in winter and spring. The flowers are pretty but it is everywhere. At least my chickens like to eat it.

Some of my invasives are no doubt on the ‘please do not sell list’ handed out to nurseries by Plant Right, a non-profit San Francisco group ( ) that works with retailers to prevent invasive plants from making their way from nurseries to our gardens. One on their list is Periwinkle (Vinca Major), an ornamental that, like Bermuda grass, is very invasive. According to UC IPM website, species that rapidly colonize an area are often called exotic invasives. The important biological difference between invasive plants and garden weeds is the ability of invasive plants to disperse, establish, and spread without human assistance or soil disturbance. Because of this, they are much more problematic in natural environments than are typical weeds. Shade tolerant Vinca major has taken over large areas under redwoods on the north coast and it is trying to take over my landscape, but so far I have kept it stymied for 40 years, but not eliminated.

Another invasive that has naturalized in my landscape is Italian arum (Arum italicum). It multiplies by seed and bulblets, so I pull all the seed stalks each year, but the bulbs are difficult to deal with effectively. Covering them with a board for 2 years can work, but that is hard to do a big scale. I see this Arum advertised in nursery catalogues and wince at the garden misery it will bestow on the unlucky buyer.

The year is young and crabgrass, pigweed, lambsquarter and others will be germinating soon to keep gardeners like me off the streets and out of the bars. Happy weeding!

If you need help identifying weeds or suggestions for controlling them, this IPM website will help:

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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    Lee Miller

    Lee Miller is a University of Delaware graduate and retired fisheries biologist, he gardens on 10 acres and makes wine each year with the help of a cadre of friends. However, his first love is gardening and he grows various fruit trees, heirloom ... Read Full

    Marcy Sousa

    Marcy Sousa is the San Joaquin County UC Master Gardener Program Coordinator. She is a Stockton native and enjoys teaching others about gardening. She has her bachelors from Stanislaus State in Permaculture. She has been with the program since 2007. Read Full

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    Nadia Zane is a UC Master Gardener, a landscape designer and Stockton native. She has a fondness for California native plants and sustainable landscaping, which she utilizes in her work for Native Beauty Garden Design. She is a member of the CA ... Read Full
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