When a citrus tree (Citrus spp.) bears abundantly, it's a good sign everything's in order. The tree is receiving the care it needs, and it's responding naturally. When mature trees fail to bear fruit, it's just as certain that something has gone awry. You can help your tree get back on track with some detective work and appropriate corrections.
Check the Area
Good citrus starts with varieties suited to your garden's conditions. Depending on the variety involved, citrus may be hardy from U.S Department of Agriculture plant hardiness zones 9 through 11. In general, citrus need a minimum of six to eight hours of direct daily sun to bloom and fruit normally.
Citrus can also take several years to get to fruiting age. Lemons (Citrus limon, USDA 9 through 11), for example, take three to four years before they start producing fruit. If you've just planted the trees, be patient.
As citrus tree grow, so do surrounding trees. What once was a sun-filled site becomes shaded. Make sure your tree's site allows for its mature size, including branches and roots. Citrus that experience too much competition from surrounding trees and plants may fail to bear fruit on schedule. If necessary, rearrange the surroundings or trim nearby plants to allow more sun to get to the trees.
Soil and Water
Citrus trees have shallow roots that need fast-draining soil with excellent aeration and consistent moisture. Soil pH near a range of 6.0 to 7.5 is best. Never let drought conditions develop and continue around your citrus. This is especially true when the citrus are blooming. If the soil dries out completely, blooms may drop -- eliminating any chances of fruit.
Always water citrus trees so the entire root zone -- all the area under the tree's canopy -- receives water. Whenever the top 2 to 3 inches of soil are dry, water well again. A well-watered tree stays healthier, more disease resistant and more productive.
Address Nutrient Needs
Citrus trees depend on abundant nitrogen for plentiful crops. If your tree lacks proper fertilizer, it may fail to bear. An annual 1/2-inch layer of well-composted manure helps citrus trees stay productive. As an alternative, use ammonium nitrate. Make three applications of this 33-0-0 fertilizer each growing season to help your tree return to fruiting. Time the first application in spring and last one in August, with the second application halfway between.
Spread 2 pounds of ammonium nitrate during each application for mature trees. Cover the entire area out to the tree's drip line and slightly beyond, and then water the area well. Don't fertilize citrus trees later than August, or you risk stimulating growth and slowing the tree's preparation for winter. Delayed dormancy reduced cold hardiness and impacts future blooms and fruit.
Timely pruning helps citrus trees stay productive and lets fruit-enhancing sunlight and air penetrate the canopy. Prune citrus trees in late spring or early summer, never in early spring. Early spring leaves help replenish the tree's energy stores after winter. Save major pruning for winter, when newly exposed branches are less susceptible to sun damage, but remove suckers growing from the tree's base any time of year -- whenever you see them.
Wear protective clothing, including gloves and protective eyewear, whenever pruning citrus -- and watch out for citrus thorns. Use sharp bypass pruners, bypass loppers or a pruning saw for crisp, clean, fast-healing cuts. Limit the accidental spread of disease and insects by sterilizing your pruning blades by spraying them with household disinfectant before and after you prune.