Site Selection
Most citrus plants are adapted to warmer, tropical or subtropical climates. Choose a site with well-drained soil that receives full sun most of the day and is protected from strong winds. Do not plant citrus in a lawn or with other plants that require frequent irrigation.
Depending upon the variety, citrus trees are generally damaged at temperatures below about 24° F and fruit, depending upon the stage of ripening, can be damaged at temperatures below 26° F. Cold-temperature sensitivity depends on many factors such as how long it stays cold, the weather prior to the cold, the position or exposure of your tree, the variety, and fruit maturity.
Some citrus also need warm summer climates for the fruit to ripen properly. If the location is too cool, the fruit quality will be poor with little sugar production in the fruit. In cooler summer areas it may take months longer for the fruit to reach an adequate sugar percentage to be harvestable. If you are in a cool summer area, try to plant on the south side of a dark wall to increase the heat units and improve fruit quality.
Planting
Planting citrus properly is critical for the success of citrus in the home garden. Containerized citrus can be planted almost any time of year. The best time is after the last frost in spring.
Trees should be planted at the same depth as they were in the container. If planted too deep, soil and water tend to stand against the trunk, which promotes root and crown rots such as Phytophthora or oak root fungus. If planted too high, the roots will dry out too quickly.
Dig the planting hole so the root ball sits about 1 inch above the soil line. The width of the hole should be about twice the diameter of the root ball. Make sure the bottom of the planting hole is firm to prevent the root ball from sinking. Cleanly remove broken or decayed roots. Backfill the planting hole with native soil and water in thoroughly after planting. Construct a watering basin that is about a foot away from the trunk of the tree. Keep the trunk dry as much as possible while irrigating.
Watering
Watering correctly is critical to the development of good quality fruit and allows trees to preserve a natural resistance to fungal diseases. Underwatering produces fruit that is small, and fruit will tend to sunburn. Overwatering predisposes the tree to root and crown rots.
During the heat of summer, avocados will require about 2 inches of water per week for a mature tree. Citrus will require about 4 to 6 inches of water per month. However, depending upon your soil type, this amount may be divided up into several applications.
Ideally, in hot summer climate zones, you may want to irrigate about every 7 to 10 days during the middle of the summer. You may irrigate your trees using a drip system with either two to four emitters per tree or using small microspray emitters. Under a drip system, a tree may require 45 to 60 gallons per day in the heat of summer, depending upon the climate zone and soil characteristics. The root zone of avocado and citrus trees is shallow and drippers need to be placed at the base of the trunk on newly planted trees to keep the root ball moist until roots grow into the native soil. Apply water further from the tree trunk as trees become established.
Pruning
Young citrus will not require extensive pruning. They will, however, often produce very vigorous shoots that give the tree a wild appearance. These shoots may be pruned back a bit to give a more refined appearance. Be sure to prune off any suckers that arise below the graft or bud union.
The ideal time to prune citrus is just prior to bloom or just after fruit set so the tree can adjust its fruit load during the June drop. Minor pruning can be done at any time, but avoid late-season pruning, which can stimulate excessive tender growth that is likely to be injured by frost. Protect any exposed branches after pruning from sunburn by painting with a 50:50 white interior latex paint and water mixture.
Thinning
Fruit thinning is not usually required. After petal fall, the young fruit undergo rapid cell division. It is not uncommon for many small pea-sized fruit to drop about 1 month after bloom. Later in spring and early summer, larger golf ball-size fruit may drop if conditions that limit growth such as excess heat, lack of soil moisture, or adverse weather exist.
Training
For a large fruiting area, citrus should be trained to be a full skirted tree with the foliage canopy extending almost to the soil line. Citrus can also be grown as a sheared hedge or informal espalier. Pruning is not required to keep citrus productive or attractive. You can, however, prune the branches up higher to make it easier to get under the tree. Try to keep the center somewhat open by removing crossing branches.
Fertilizing
Citrus occasionally suffers from micronutrient deficiencies such as zinc or iron. These deficiencies can be corrected by applying a foliar application of a liquid chelated micronutrient solution as the new growth emerges in the spring. You can also apply micronutrients in the sulfated form, such as zinc sulfate or iron sulfate, to the soil.
Most mature citrus require regular fertilization with nitrogen. Typically, most other nutrients are available in sufficient amounts in the soil. Nitrogen should be applied in January or February just prior to bloom. The second application then can be applied in May and perhaps a third in June. Avoid late-season fertilization as it may affect fruit quality, delay fruit coloring, and make the rind rough. Dwarf plants or trees in containers with restricted root space may require less fertilizer.
Maintaining a good fertilizing program can help preserve a tree's natural resistance to fungal diseases such as oak root fungus. Be careful not to overfertilize as this will cause excessive new growth, which makes trees susceptible to other disorders such as bacterial blast.
Suggested Application Rates of Nitrogen
- 1st year: 1 tablespoon nitrogen fertilizer 3 times per year, per tree.
- 2nd year: 0.25 lb actual nitrogen per tree
- 3rd year: 0.5lb actual nitrogen per tree
- 4th year: 0.75lb actual nitrogen per tree
- 5th year:1 lb actual nitrogen each year
1 pound of actual nitrogen equals about 5 lb of ammonium sulfate per year, or 100 lb of composted cow manure each year. Organic fertilizers such as manure, bloodmeal, etc. could be applied in the fall under the tree canopy.
Harvesting and Storing
Fruit should be harvested when it has developed full color and, most importantly, full flavor. Some varieties, such as Valencia oranges, may be greenish in appearance but still fully ripe. Citrus turn color in fall when they are exposed to cold temperatures, but this does not affect the fruit sweetness. Navel oranges may not be ready to harvest until the late winter, and Valencia oranges are usually mature in the summer.
The best place to store the fruit is on the tree. Once you pick the fruit, it does not increase in sweetness or ripen more fully. However, if you do pick the fruit, it will keep for about 4 to 6 weeks under refrigeration.
Juice from lemons, limes, and Valencia oranges can be frozen for up to 4 months.
Sanitation
Sanitation is a necessary management tool in all home orchards because of the long life of trees. Perennial weeds, nematodes, and certain disease pathogens are difficult to control after trees become established. Prevent the introduction or spread of infestations by removing infected limbs and fruit. Disinfect cutting tools periodically during pruning and whenever they come into direct contact with diseased tissue. Clean equipment used in other areas to avoid introducing pathogens, nematodes, or weeds.
Sanitation Tips
- Remove diseased wood as soon as it becomes evident. Dispose of the prunings immediately to prevent them from becoming a source of new infections.
- Remove stumps, brush piles, and debris. Brush, thinnings, and other debris can harbor diseases as well as vertebrates and insects. Removing stumps may prevent population buildups of wood-boring insect pests.
- Remove diseased shoots, leaves, and fruit on trees and on the ground.
- Remove roosting, nesting, or resting areas that may attract large numbers of crop-destroying birds.
- Keep the tree crown area free of weeds to reduce crown rot infections.
- Spot-treat perennial weeds to prevent their spread.
