It is time to consider caring for your citrus or planting some if you have none and want to enjoy picking your own ripe tangerines, oranges, lemons, limes, pummelos, and grapefruit. There are lots of citrus suitable for planting in San Joaquin County. One of the best to plant is a dwarf, Improved Meyer lemon. It is a highly productive variety that is somewhat freeze resistant and will keep you in lemons for a few months annually. Meyer lemons are a little sweeter than other lemons. I have one that is about 40 years old and still going strong and very productive. It can be planted in containers as well as in the ground, but if you want to give it room with less fuss—plant it in the ground. Folks in parts of the country where it freezes can grow them in containers so they can be moved to a warm spot for the winter.
If you want a more tart lemon, I can recommend ‘Lisbon’ which is less likely to be damaged by freezing temperatures than the ‘Eureka’ variety. The Lisbon or Eureka lemon both require more diligent pruning than the Meyer. They tend to grow more vigorously, with long straggly branches. Hence, they need pruning to keep them stubby and supportive of the fruit that they abundantly produce.
When to prune citrus, is a question often asked of Master Gardeners. The ideal time is in the spring after any frost damage can be observed and removed and before new growth occurs or summer heat sets in. Spring is also the best time to purchase and plant new citrus trees. Pruning out water sprouts (gourmands) may improve yields because more energy can go toward fruit production. Water sprouts will not produce fruit. Pruning can improve fruit quality through increasing light in the canopy. In older trees, reducing tree height facilitates harvesting and reduces risk of injury from ladders. The best approach is to plant dwarf trees and avoid heights where possible. Skirt pruning facilitates weeding, mulch additions, and other cultural practices, as well as reducing risk of soil borne pathogens affecting the fruit. Pruning may reduce insect and disease pest problems.
If you have older trees, say greater than 40 years old, it is good to disinfect pruners after pruning and before pruning younger trees. Use of disease free budwood and rootstock in more recent years has reduced the incidence of these diseases. Older trees are more likely to harbor viruses and they may be spread by the pruning tools if not disinfected. A 15 percent bleach solution or Lysol can be used to disinfect pruners.
I had a Valencia orange that was over 50 years old and it developed Psorosis, a virus disease causing shelling of bark on the scion caused by a virus. It was also common on old trees before it was eliminated in nursery stock. My Valencia, which produced lots of oranges for several years, finally declined over time and had to be removed. It will take my young Valencia many years to become as productive as that old tree.
As with any tree pruning it is important not to damage or remove the branch collar which produces the tissues which heal the wound. The branch collar is the area around the base of a large branch, often visible as a ridge or wrinkled bark around the branch. It contains a narrow band of cells known as the “branch defense zone” which activate the growth of the callus tissue that grows over the pruning cut. Citrus bark is also thin and easily damaged so care should be taken not to scar the bark.
In order to shape a young tree, downward growing shoots should be pruned to allow upward growing buds to become dominant. Cutting the shoot just above an axillary bud (the bud in the angle between the leaf and the stem) pointing upward will redirect growth upward. This will help shape the tree for future production.
Beware of any shoots that are thorny and originate below the scion wood on the rootstock. These shoots below the bud union should be removed as soon as they appear. For trees on Trifoliate rootstocks (Poncirus trifoliata), the thorns from the rootstock are very obvious and hazardous to your skin.
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: http://sjmastergardeners.ucanr.edu/CONTACT_US/