DESCRIPTION

TREE

Medium to large tree (30–40 ft [ 9.1–12.2 m]; up to 115 ft [35 m]) in tropical areas) with a pyramidal or oval canopy. The secondary and tertiary branches that emerge from the main limbs are generally willow-like (thin and long) and hang downward when heavy with fruit.

LEAVES

Alternate, oblong to elliptic, 4–8 inches (10–20 cm) long and 1 ¼–2 3/8 inches (3.2–6.0 cm) wide.

INFLORESCENCE (FLOWERS)

The flowers are borne singly or in a clusters of 2–5 flowers in leaf axils on long, thin shoots. Flowers are hermaphroditic, small, 4- to 5-lobed, cylindrical, and white to greenish. Flowers open during the morning and may stay open for about 2 days.

FRUIT

Ovoid to round, 1 ½–4 inches (3.8–10.2 cm) in diameter, 10 –25 oz (283–708 g), commonly with a short nipple at the apex. The peel is smooth, tough, and pale to bright yellow when ripe. The pulp is white, translucent, jelly-like, mild-flavored, and sweet in better selections and insipid in undesirable trees. There are 1–5 brown seeds. Immature fruit is permeated with unpleasant, gummy latex; fully ripe fruit have little to no latex. Fruit take 100–130 days from flowering.

POLLINATION

No specific information on the pollination requirements or pollinators (insects) of abiu has been documented. Flying insects are probably the pollinators.

VARIETIES

There are a number of abiu varieties (e.g., 'Gray', 'Z-2'); however, few selections or varieties are available in Florida. There is a lot of variability among seedling trees.

CLIMATE

Abiu grows best in hot, humid, tropical climates with well distributed rainfall. Trees may grow well in warm, humid, subtropical areas if protected from constant winds and freezing temperatures. Optimum growth temperatures are from 68–95°F (20–35°C). Abiu trees are sensitive to cool, non-freezing temperatures and windy conditions, and should be planted only in warm, wind-protected areas. Young trees may be killed at temperatures below 32°F (0°C) and mature trees at 29–31°F (-0.5– -1.6°C).

PROPAGATION

Abiu is commonly propagated by seed; seedling trees usually begin fruit production in 3–4 years after planting. Once extracted from the fruit, abiu seeds do not remain viable for more than a couple of days and should therefore be planted as soon possible into clean, well-drained media. Seedling trees come into production in 2–5 years from planting. Abiu may also be grafted or budded onto seedling rootstocks and begin fruiting in 1–2 years.

PRODUCTION (CROP YIELDS)

The amount of fruit produced varies greatly among abiu seedling trees. Some mature seedling trees may produce little fruit; others yield 400 lbs (182 kg) of fruit per year. Historically abiu season in Florida has been during the fall.

SPACING

Abiu trees should be planted at least 25 ft (7.6 m) from nearby trees and structures because mature trees not regularly pruned may become quite large.

SOILS

Abiu trees are best adapted to fertile, acid- to slightly-alkaline-pH (5.5–7.5), well-drained soils. Trees growing in high-pH, alkaline soils may develop iron deficiency.

PLANTING AN ABIU TREE IN THE HOME LANDSCAPE

Proper planting is one of the most important steps in successfully establishing and growing a strong, productive tree. The first step is to choose a healthy nursery tree. Commonly, nursery abiu trees are grown in 3-gallon (11-liter) containers and trees stand 2–4 ft (0.6–0.9 m) from the surface of the soil media. Large trees in smaller containers should be avoided as the root system may be "root bound." This means all the available space in the container has been filled with roots to the point that the tap root is growing along the edge of the container in a circular fashion. Root bound root systems may not grow properly once planted in the ground. Inspect the tree for insect pests and diseases, and inspect the trunk of the tree for wounds and constrictions. Select a healthy tree and water it regularly in preparation for planting in the ground.

SITE SELECTION

In general, abiu trees should be planted in full sun for best growth and fruit production. Select a part of the landscape away from other trees, buildings and structures, and power lines. Remember, abiu trees can become large if not pruned to contain their size. Select the warmest area of the landscape that does not flood (or remain wet) after typical summer rainfall.

PLANTING IN SANDY SOIL

Many areas in Florida have sandy soil. Remove a 3- to 10-ft-diameter (0.9–3.1 m) ring of grass sod. Dig a hole 3–4 times the diameter and 3 times as deep as the container the abiu tree came in. Making a large hole loosens the soil next to the new tree, making it easy for the roots to expand into the adjacent soil. It is not necessary to apply fertilizer, topsoil, or compost to the hole. In fact, placing topsoil or compost in the hole first and then planting on top of it is not desirable If you wish to add topsoil or compost to the native soil, mix it with the excavated soil in no more than a 1:1 ratio.

Backfill the hole with some of the excavated native soil. Remove the tree from the container and place it in the hole so that the top of the soil media from the container is level with or slightly above the surrounding soil level. Fill soil in around the tree roots and tamp slightly to remove air pockets. Immediately water the soil around the tree and tree roots. Staking the tree with a wooden or bamboo stake is optional. However, do not use wire or nylon rope to tie the tree to the stake because they may eventually damage the tree trunk as it grows. Use a cotton or natural fiber string that will degrade slowly.

PLANTING IN ROCKLAND SOIL

Many areas in Miami-Dade County have a very shallow soil, and several inches below the soil surface is hard, calcareous bedrock. Remove a 3- to 10-ft-diameter (0.9–3.1 m) ring of grass sod. Make a hole 3–4 times the diameter and 3 times as deep as the container the abiu tree came in. To dig a hole, use a pick and digging bar to break up the rock or contract with a company that has augering equipment or a backhoe. Plant the tree as described for sandy soils.

PLANTING ON A MOUND

Many areas in Florida are within 7 ft (2.1 m) or so of the water table and experience occasional flooding after heavy rains. To improve plant survival consider planting fruit trees on a 2- to 3-ft-high by 4- to 10-ft-diameter (0.6- to 0.9-m by 1.2- to 3.1-m) mound of native soil. After the mound is made, dig a hole 3 to 4 times the diameter and 3 times as deep as the container the tree came in. In areas where the bedrock nearly comes to the surface (rockland soil), follow the recommendations for the previous section. In areas with sandy soil follow the recommendations from the section on planting in sandy soil.

CARE OF ABIU TREES IN THE HOME LANDSCAPE

A calendar outlining the month-to-month cultural practices for abiu is shown in Table 1.

FERTILIZER

In Florida, young trees should be fertilized every 1–2 months during the first year, beginning with 1/4 lb (114 g) of fertilizer and increasing to 1 lb (455 g) per tree (Table 2). Thereafter, 3 or 4 applications per year in amounts proportionate to the increasing size of the tree are sufficient, but do not exceed 20 lbs per tree per year.

Fertilizer mixtures containing 6–10% nitrogen, 6–10% available phosphoric acid, 6–10% potash, and 4–6% magnesium give satisfactory results with young trees. For bearing trees, potash should be increased to 9–15% and available phosphoric acid reduced to 2–4%. Examples of commonly available fertilizer mixes include 6-6-6-2 [6 (N)-6 (P₂O₅)-6 (K₂O)-2 (Mg)] and 8-3-9-2 [8 (N)-3 (P₂O₅)-6 (K₂O)-3 (Mg)].

From spring through summer, trees should receive 3 to 4 annual nutritional sprays of copper, zinc, manganese, and boron for the first 4–5 years. Abiu trees are susceptible to iron deficiency under alkaline and high-pH soil conditions. Iron deficiency can be prevented or corrected by periodic soil applications of iron chelates formulated for alkaline and high-soil-pH conditions. Periodic applications of ferrous (iron) sulfate may be made to trees growing in low-pH soils.

IRRIGATION (WATERING)

Newly planted abiu trees should be watered at planting and every other day for the first month or so and then 1 to 2 times a week for the next couple of months. During prolonged dry periods (e.g., 5 or more days of little to no rainfall), newly planted and young abiu trees (first 3 years) should be well watered twice a week. Once the rainy season arrives, irrigation may be reduced or stopped.

Once abiu trees are 4 or more years old, irrigation will be beneficial to plant growth and crop yields during prolonged dry periods. The specific water requirements for mature trees have not been determined. However, as with other tree crops, the period from bloom and through fruit development is important, and drought stress should be avoided at this time with periodic watering.

ABIU TREES AND LAWN CARE

Abiu trees in the home landscape are susceptible to trunk injury caused by lawn mowers and weed eaters. Maintain a grass-free area 2–5 or more feet (0.6–1.5 m) away from the trunk of the tree. Never hit the tree trunk with lawn mowing equipment, and never use a weed eater near the tree trunk. Mechanical damage to the trunk of the tree will weaken the tree and, if severe enough, can cause dieback or kill the tree.

Roots of mature abiu trees spread beyond the drip-line of the tree canopy. Heavy fertilization of the lawn next to abiu trees is not recommended because it may reduce fruiting and or fruit quality. The use of lawn sprinkler systems on a timer may result in over watering and cause abiu trees to decline. This is because too much water too often applied causes root rot.