Subtropical Fruit Choice Wide From Avocado to Tamarind

by Robert J. Knight, Jr., and Julian W. Sauls.

Robert J. Knight, Jr., is Research Horticulturist, Agricultural Research Service, Miami, Fla. Julian W. Sauls is Extension Horticulturist, University of Florida, Gainesville.

Subtropical fruits number over a hundred and range from avocado and citrus to soursop and tamarind. Thus the information in this chapter has to be general rather than specific and you should seek more detailed advice from your county Extension office. Nurserymen can be most helpful too, as can experienced gardeners, garden clubs, or other specialized groups such as the rare fruit organizations active in Florida and California.

Fortunately, cultural requirements for most subtropical fruits do not differ from those of other shrubs, trees or vines grown for fruit, ornament, shade or other specialized use. In fact the outstanding ornamental value of most fruit crops fits them admirably for a dual role.

Because they come from many parts of the world with varied environmental conditions, subtropical fruit crops differ in the degree of cold they can withstand and in soil and moisture requirements. Some are adapted to warm-temperate conditions, and others are tropical plants which will tolerate brief cold spells and thus survive winters in the warmest parts of the continental United States.

When you select fruits to plant around Your home, choose those known to grow well in your locality. Otherwise you may go to a lot of trouble to grow a plant that may prove disappointing, despite your best efforts. Your own personal preferences, tempered by knowledge of what grows well in the area, should determine what you plant.

Most tree fruits should be planted 12 to 20 feet apart and away from the house, walks, drives, and power lines. Those tropical fruits listed as small trees or shrubs at the end of the chapter can be planted somewhat closer. Where there is significant danger of cold damage, plant subtropical fruits in the warmest part of the yard, which generally is the south side of the house.

Most failures in growing fruit trees at home can be attributed to poor transplanting or poor care. Commercial fruit growers routinely transplant fruit trees with almost no failures.

Good preparation of the planting hole is essential. Dig the hole only as deep as and about a foot wider than needed to accommodate the root system. Regardless of your soil type, it would probably benefit from the addition of liberal amounts of organic matter such as rotted manure, compost or peat.

For bare-root plants, prune off dead or damaged roots. Make a cone of soil in the center of the hole and set the plant on it, carefully spreading the roots out in the hole. For container-grown plants, remove the container and set the plant in the hole.

In either case, set the plant at the same depth it was growing in the nursery or container.

Fill the hole three-fourths full of soil. Then fill with water to settle soil around the roots and eliminate air pockets. After the water drains through, finish filling the hole with soil, then water again. A ring of soil a few inches high around the planting hole can be used to form a watering basin during the first year.

At planting, bare-root fruit trees should be pruned to balance the top with the reduced root system, which requires removing about a third of the top. Most people are reluctant to prune this heavily, but it's for the good of the tree. If you're unsure about doing the job right, have the nursery where you bought the tree do it for you. Container-grown plants are not usually pruned since they have an intact root system.

Training

Initial training of the fruit tree is done at planting to assure that the tree takes the desired shape. For example, the growing tips of branches are pruned off to force branching. Even so, most subtropical fruit trees are not trained appreciably, but simply allowed to develop naturally.

Mature trees are pruned to remove dead or damaged wood, or to eliminate limbs that may interfere with traffic in the yard. Such pruning can be done at any time of year.

Pruning cuts should be clean and close to the trunk to avoid leaving stubs which enable wood-rotting organisms to enter the tree. Protection with pruning paint is recommended if the cut is larger than an inch or so in diameter.

Subtropical fruit trees are not in such prominence that they require "special" fertilizers as yet. You cannot run down to the garden center and pick up a bag of "Kiwi Special" or "Atemoya and Cherimoya Food". Fortunately, subtropical fruits will grow just as well on a complete, balanced garden fertilizer such as 6-8-8, 10-10-10, or 12-12-12. However, if your area has alkaline soils or soils known to lack specific micronutrients such as iron, manganese or zinc, these may need to be supplied.

Newly planted trees should not have fertilizer until they resume active growth after transplanting. Then, fertilize sparingly and frequently until they mature and begin to produce fruit. Using 10-10-10 as an example, young trees should receive about a pound of fertilizer per year of tree age, that is, 1 pound in the first year, 2 in the second, and so on. Total fertilizer for the year should be divided into several applications so young trees receive some fertilizer every 2 to 3 months.

Mature, bearing trees can be fertilized at double that rate, or 2 pounds per year of tree age. Thus, a 10-year-old tree would receive 20 pounds per year, which would be split into 3 applications early spring, early summer and early fall. Fertilizer can be spread on the ground under the tree and then watered in.

Lime may be needed in some cases to raise the soil pH so it is suitable for optimum tree growth. However, liming should be based on a soil test and recommendation from the county Extension agent.

Occasionally, some fruit trees may need certain micro-elements, particularly in very sandy soils or alkaline soils. Micro-elements are included in some fertilizers and are also available in nutritional sprays which are applied separately as foliar (leaf) sprays. In all cases follow recommendations of your county agent.

Mulches

Mulches around fruit trees help in weed control and water conservation. They also reduce lawn mower damage to tree trunks since you don't need to mow close to the trees.

In some cases, organic mulches can lead to fertilizer deficiencies as the micro-organisms that decompose them rob nutrients the tree could use. They also contribute to increased cold damage by inhibiting radiation of ground heat to the tree. In other cases, organic mulches increase the incidence of diseases such as foot rot and root rot. For these reasons, we recommend clean cultivation instead of mulches for citrus, avocado, lychee and some other fruits.

Mulches from your yard could include leaves and grass clippings. Or you can obtain sawdust, wood chips, pine bark, gravel and other mulches from local nurseries.

A lot of gardeners don't understand about watering plants. This is one reason why so many fruit trees die shortly after transplanting. Too little water causes the tiny root hairs to die, and the leaves then wilt for lack of water. On the other hand, too much water forces air from the soil, again causing the root hairs to die for lack of oxygen, and the leaves will wilt. For best results, water fruit trees infrequently but thoroughly.

Frequent, shallow waterings cause shallow rooting. A shallow-rooted fruit tree is subject to drought and poor growth. Consequently, when you water, water long and water well. Apply water only as fast as the soil can absorb it and keep watering until the soil is wet at least a foot down.

Newly transplanted trees need a good soaking every 2 to 4 days until they are well established. Mature trees need water every 7 to 12 days, depending on the climate and soil type. Since sandy soils don't hold much water, they require watering about once a week, while clay soils will go several days longer before drying out.

Fruit trees growing in the lawn area will compete with the lawn for fertilizer and water. In such situations pay particular attention to needs of both tree and lawn. The tree will compete much more aggressively than the grass. The grass will soon begin to thin out and may disappear completely once the tree begins to create heavy shade.

Cold protection often is required for many subtropical fruits. Young trees are more susceptible to cold than large, mature trees, but also easier to protect. Banking a mound of soil around the trunk of a young fruit tree will keep the rootstock and trunk alive even if the top should freeze. Pull the bank down in spring after cold danger is past.

Small trees can be covered with blankets, paper or plastic to prevent freezing. Lawn sprinklers have been turned on trees, but too much water can cause problems for the root system and ice can cause limb breakage. In some cases, a frame covered with clear polyethylene can be built around the tree to form a mini-greenhouse. Some slow-burning heating materials are available and work quite well; check with your county Extension agent or nurseryman.

Most subtropical fruits have enough insect and disease problems to make growing them troublesome at times. You need to learn the potential pest problems and how to control them. To do this requires a little effort on your part in order to be able to recognize the damage before it becomes serious, identify the insect or disease responsible, and take effective remedial action before the damage progresses too far to control.