Now that we are well into spring and the last frost, we hope, has passed, this is a good time to work with citrus trees.
Because of its subtropical nature, citrus is best left undisturbed through the winter. An established citrus tree with a full canopy of mature foliage and growing on a moist, well-drained site tends to have good potential for success. In contrast, citrus that is newly transplanted, poorly drained or drought stressed, or covered with tender new growth tends to be more susceptible to winter freeze damage.
Cold-hardy fruit trees, such as apple, pear and plum have a true dormant period. As a result of adaptation to cold-winter climates, they actually require chilling every winter before they can break dormancy and grow vigorously in spring. Citrus just slows growth when the days are shorter and temperatures are lower.
Cold-hardiness, growth habit and productivity varies with the type of citrus and local microclimates but a few principles and management practices can be applied in general make a world of difference.
While cold-hardy fruit trees respond well to moderate to heavy dormant season pruning, plus some summer pruning, citrus responds and produces best when pruned for light thinning in spring through mid summer.
Citrus produces flowers on shoots that grew during the previous year, so pruning should retain plenty of 1-year-old shoots while removing the very crowded branches. This type of pruning called “thinning” moderates the amount of fruit the tree bears and it has an additional benefit: A moderate increase in space among the branches and sunlight reaching the inner canopy makes conditions less favorable to citrus pests like scale and snails.
Citrus has the ability to sprout from bare branches. When limbs break, are pruned back to stubs or severely damaged by a hard freeze they tend to generate numerous sprouts near wounds. But these soft new shoots are frost-tender and easily dislodged from the branch. Because limb sprouts and other new shoots are frost tender, it is best to avoid heavy late-summer pruning as well as late summer fertilizer applications with nitrogen that stimulates soft green growth. New growth should have time to mature before winter.
A couple of recent incidents point to the importance of what’s going on below ground. In one case, a sudden yellowing of the entire canopy of a tangelo was mysterious until a simple root collar excavation and exam revealed that a gopher had eaten the bark off the base of the trunk. In the other instance, similar symptoms were caused by root disease resulting from poor drainage.
As described in the “How to Grow Citrus” article in “The New Sunset Western Garden Book” (2012), “Fast drainage is essential. If soil drains slowly, don’t attempt to grow citrus in it regardless of how you condition it. Instead, plant above soil level in raised beds or on a soil mound.”
If you have citrus trees showing health problems you might want to check out the following link, where you can see photos of symptoms:ipm.ucdavis.edu/PMG/C107/m107bpleaftwigdis.html
As it is with so many other subjects, the closer you look, the more a world of fine detail opens up. Citrus has its own world of cultivated varieties, rootstocks, care practices, and pests and diseases.
In spite of the potential challenges, home-grown citrus can be very rewarding. Right now is a good time to get ready for planting.