Citrus trees were introduced in California by the Spanish priests who founded missions up and down the coast, and they remain a popular choice for home gardeners looking to fill their larders with lemons, oranges, tangerines and limes.
Caring for citrus doesn't have to be difficult or time consuming, as they require little attention, and healthy trees are pretty much pest-free, says Contra Costa Master Gardeners Molly Wendt and Sierra Higgins, speakers at Our Garden's weekly class.
Giving them proper water and protection from hard frosts are the keys to successful harvests. Here are their tips.
Choices Hundreds of varieties of citrus trees are available, and you should research to find the ones that do best in your particular climate. When choosing a tree, consider how large it will get. A standard tree grows to about 25 feet high; a dwarf variety averages 8 feet. Dwarf varieties are standard-sized citrus scions grown on dwarf root stock to produce an artificially smaller tree. However, Wendt cautions, nurseries aren't regulated in this area, so be sure you purchase a tree from a reputable nursery or you could discover that the dwarf you thought you had planted is actually a much taller tree. Unsure of what type of citrus to grow or limited on space? Consider a "fruit salad" tree that has been grafted with different types of citrus, allowing you to grow lemons, limes and oranges on the same tree. Before buying, examine the tree carefully. It should be healthy, have no blemishes or nicks on the bark, have no pest damage, and the bud union -- the place where the scion was grafted onto the root stock -- should be visible above the soil. Try to find trees that don't already have fruit on them -- they will transplant easier.
Planting Early spring is the best time to plant citrus, Higgins says. That will allow the tree to become established and survive the heat of summer and the cold of winter. Citrus grows best in sandy to clay loam that is well draining. Plant in a sunny location in an area that is protected from the wind. Make sure you have enough room for the tree to grow to its mature height. Citrus grown on dwarf stock can live their entire lives in containers. Just make sure to keep them watered -- container plants tend to dry out much more quickly than those planted in the ground -- and fertilized. Don't plant a citrus tree in your lawn. It will suffer from either too much or too little water. When digging a hole to plant your tree, dig it twice as wide as the root ball, but only just as deep as the pot the tree is in. Set the tree in the hole and cut the pot away. Yanking the tree out of the pot can damage fragile roots. Once the tree is in place, cover the roots with the native soil and build a dirt basin around it, 3 feet around, to retain water. Do not add amendments in the hole or after planting. You want the roots to spread out in search of nutrients, building the root system and anchoring it more firmly in the ground. For just-planted trees, fill the water basin and allow the water to saturate the root ball. Repeat the watering two more times. Add soil if it has settled. Mulch around the tree, staying 6 inches away from the tree trunk.
Water and fertilization Don't let the roots on your trees completely dry out. Although more trees die from overwatering than underwatering, it's important to keep the tree hydrated. Don't let the tree stand in water. Check the tree during the winter rains to make sure the basin isn't retaining water. If it is, smooth the barrier away to allow the water to run off. Signs that you are not watering your tree enough include the cupping of new growth (the leaves curl up to resemble cups) and fruit and leaf drop. Sign of too much water is the yellowing of leaves while the veins remain green. Citrus trees are evergreen, and they need water all year. During the winter, they will need less supplemental water if we have rain, but you'll need to keep an eye out. When watering, try to avoid getting the trunk and leaves wet. Trees should be fertilized a few times a year from late February through September. Don't fertilize in the winter, as that will encourage new growth, which then may be nipped by a cold spell. The main nutrient citrus trees need is nitrogen.
Pruning Citrus requires little if any pruning. For trees 3 years old and younger, no pruning should be done. After that, prune carefully and judiciously, mostly to keep growth in check and to remove damaged limbs, disease, dead wood and limbs that might endanger the health of the tree. Use horizontal cuts to promote new growth.
Harvesting Some trees, such as lemons, produce year round. Others ripen at different times throughout the year. Check the variety you are growing to determine when fruit should ripen. Don't go by the rind color to determine ripeness. Some fruit that looks green may actually be perfectly ripe. The best place to store your citrus is on the tree. Pick as needed. It also will keep in the refrigerator for up to six weeks.
Not a problem
These are common problems that aren't problems at all. Leaves drop from citrus trees regularly. Leaves live for one to two years, then replace themselves. Yellowing of leaves is normal during cooler temperatures. The tree will green up in the spring. If your tree doesn't produce much, or any, fruit in the first three years, don't worry. That's natural. Production will increase after three years. Flower and fruit drop isn't always a sign of trouble. Often the tree self-regulates, dropping blooms and fruit if it has produced too much. An excessive drop of fruit is likely due to lack of nitrogen. However, don't apply nitrogen during the winter.
About Our Garden
Free gardening classes are offered 10-11 a.m. Wednesdays at the garden, Wiget Lane and Shadelands Drive in Walnut Creek. Master Gardeners also are available to answer questions at the Help Desk; plants, seeds and worm compost also are available for sale most weeks.
Next time: "Tips and Tools from Master Gardeners." This will be our last class of the season. Come visit us in April for a new year of growing and sharing.
-- Joan Morris, Staff