Growing Citrus Trees

Growing Citrus Trees Citrus trees form a family of sub-tropical evergreens. Even in winter, they never become fully dormant and thus lack the deciduous tree's ability to protect itself against freezing weather. Most produce fruit with rinds of varying thickness and pulpy, juicy flesh.

For the home landscaper, the most popular members of the citrus family are mandarins (satsumas, tangerines, etc.), oranges, grapefruits, kumquats, calamondins, lemons and limes. There are also varieties of tangerine and lime hybrids. Generally, kumquats and members of the mandarin group, including tangerines and satsumas, are considered to have the highest level of resistance to cold. Grapefruits and limes are considered to be the most cold-sensitive. All, however, require help in order to survive sharp or sustained freezes defined as periods when the temperature drops to the low 20s (°F) or below.

Orange
Grapefruit
Mandarin
Lemon
Lime
Kumquat

Planning

Citrus trees bear a variety of fruits; lemons, limes, oranges, kumquats, grapefruits, etc. For those gardeners in zones 9-11, you can plant citrus trees any time of year, although spring is the best time to plant nursery grown trees outdoors. Gardeners in zone 8 can also plant citrus year-round, as long as they plant cold tolerant types. For those in zones 7 and north, potted citrus can be grown anytime, but needs to be kept indoors when cold temperatures arrive and provided sufficient humidity. Most citrus trees (not all) are self-pollinating so you can harvest a whole crop from just one tree.

Sample fruits from stores and markets to determine which cultivar to grow. Trees will start to bear fruit at about 3 to 6 years of age.

Site Preparation

Citrus trees need sites with full sun and protection from strong winds. In areas of extreme heat, they will benefit from partial shade. Soil should be deep, nutrient-rich and well-drained and have a pH slightly on the acidic side (6.0 to 6.5). Avoid low lying sites subject to frost and standing water and soil containing high concentrations of salt.

Planting

Plant bare-root trees so that the graft unions are at least 6 to 8 inches above the soil level, but so the tree is planted deeper than it was in the nursery container. Spacing will depend on the type and variety planted, but in general trees should be spaced at least as far apart as their mature height. Young trees should be watered deeply once per week, especially during the first season. Spread 3 to 4 inches of organic mulch around the tree after planting, leaving 3 to 4 inches around the base of the trunk bare.

Care & Maintenance

Most citrus trees are self-shaping and need very little pruning. Root suckers or crossing branches can be removed as necessary on young trees and mature trees should be kept free of dead, broken or diseased branches. Apply an organic fertilizer to trees once each season-spring, summer, winter and fall. How much will depend on the size of your tree, so consult with the nursery who sold you the tree. Inspect trees once per week for pest problems and signs of disease. To prevent sunscald and pest damage in cooler zones, paint trunks with diluted white latex paint or wrap them with tree tape in preparation for winter. This should also be done to any branches suddenly exposed to full sun as a result of pruning.

Pests & Diseases

Pests:

Follow directions on the chemical packaging precisely. Remember to pay particular attention to the time from when you spray until when you can safely eat the fruit.

Borers - may cause die back of limbs that are badly affected. Severely damaged limbs should be completely removed. Pour MALATHON or CONFIDOR concentrate into the holes to kill the insect and spray STERIPRUNEover the damaged bark to stop wood-rotting fungus disease.
Bronze Orange Bug - these insects suck the sap from new shoots. Control the problem with FOLIMAT, CONFIDORor MALATHONas recommended.
Caterpillars - several types of these pests attack citrus. Spray with MAVRIK, success, DIPEL or pyrethrum to control.
Fruit Fly - these puncture the fruit causing it to discolour and become infected with larvae. Spray with NATRASOAP or lebaycid watching timing of spray to final harvest of fruit.
Scale - various types of scale affect citrus trees. WHITE OIL, PESTOIL or SCALE GUN should get rid of these. Bad infestations may need spraying twice two weeks apart.

Diseases:

Follow the directions on the chemicals precisely. Remember to pay close attention to the time from when you spray until when you can safely eat the fruit.

Black Spot - this fungus causes slightly sunken brown or black spots on the fruit. Common on Valencia oranges grown in humid coastal areas. Spray with TRIFORINE, ZINEB, COPPER OXYCHLORIDE or MANCOZEB plus.
Collar Rot - the bark splits and becomes soggy near the base and gum may be exuded (this is caused by a fungus). Clean away the damaged bark and spray with ANTI-ROT. Seal the wound with a dressing such as STERIPRUNE.
Melanose - this fungus disease causes a brown stain or clusters of tiny brown spots on the fruit, leaves and stem. It may accompany die back of twigs.
Sooty Mould - this is a symptom of scale or aphid attack. It grows on the honeydew excreted by these pests. Spraying with COPPER OXYCHLORIDE will kill this problem but the pests causing it must also be controlled. FOLIMAT and clear white oil combined may be useful.

Other Problems

Mineral Deficiencies - there are various mineral deficiencies that affect citrus occasionally. The most common are:
Iron - yellowing mainly of new growth with the veins standing out in green. This is caused by liming too heavily or alkaline soil. Spray and water plant with IRON CHELATES at the recommended rate.
Magnesium - this causes yellowing mainly of the mature leaves starting as a blotch and spreading to a characteristic inverted V shape at the leaf tip and may cause leaves to fall prematurely. Branches carrying the most fruit are usually the most affected. Water the soil around the base of the tree. Mix 2 tablespoons of MAGNESIUM SULPHATE (EPSOM SALTS) with 10 litres of water and soak 8 litres of this into the soil. Spray the tree with remaining 2 litres. It may take several months to correct this problem but the new growth should be green.

Harvesting & Storage

Citrus fruits should be harvested when the fruit shows mature color. Taste testing throughout the harvest season is the only sure way to determine fruit is ready. Remove only what you can consume at one time. Most ripened fruit will keep for weeks ( sometimes months) hanging on the tree. Large amounts of fruit can be kept fresh in the refrigerator for up to several months.