When is the Best Time to Plant an Avocado Tree?

A medium (30 ft; 9. 1 m) to large (65 ft; 19. The avocado tree is a large (Figure 2) evergreen tree, though some types lose their leaves for a short time before and during flowering. The tree canopy ranges from low, dense and symmetrical to upright and asymmetrical. Limbs are easily broken by strong winds or heavy crop loads.

Leaves are 3 to 16 inches (7. 6 to 41. 0 cm) in length and variable in shape (elliptic, oval, lanceolate) (Figure 3). They are often hairy (pubescent) and reddish when young, then become smooth, leathery, and dark green when mature.

The many-flowered lateral inflorescences (structures that hold the flowers) are borne in a pseudoterminal position (Figure 4). The central axis of the inflorescence terminates in a shoot. Flowers are perfect, yellowish-green, and 3/8 to 1/2 inch (1 to 1. 3 cm) in diameter (Figure 5).

The fruit is a berry, consisting of a single large seed, surrounded by a buttery pulp (Figure 6). Florida avocado varieties contain 3 to 15% oil. The skin is variable in thickness and texture. Fruit color at maturity may be green, black, purple or reddish, depending on variety. The fruit can be round or pit-shaped, and it can weigh anywhere from a few ounces to five pounds. 3 kg). The fruit does not generally ripen until it falls or is picked from the tree. In Florida, the fruit is ready to be picked when it reaches a certain date on the calendar and a certain weight or size. The specific dates, weights, and sizes used to determine maturity vary by variety.

Avocado flowers are bisexual, however, the female and male flower parts function at different times of the day. Different kinds of plants are divided into A and B types based on what time of day the female and male flower parts start to reproduce. New evidence indicates avocado flowers may be both self- and cross-pollinated under Florida conditions. When the second flower opens, pollen from the anthers moves to the stigma of the female flower parts. This is called self-pollination. Cross-pollination may occur when female and male flowers from A and B type varieties open simultaneously. Cross-pollination is done by big flying insects like bees and wasps, while self-pollination seems to be mostly caused by wind.

Varieties vary in the degree of self- or cross-pollination necessary for fruit set. Some varieties, such as Waldin, Lula, and Taylor fruit well when planted alone. Others, like Pollock and Booth 8 (both B types), don’t, so it’s probably best to plant them with A types that bloom at the same time to make sure they get enough pollen and fruit. Before planting an avocado tree, homeowners should scout their neighborhood for other home landscapes with avocado trees. If you live in an area with other avocado trees, planting just one will probably be enough to get enough pollination. If there aren’t any other avocado trees nearby, you may choose to plant two, one an A-type and the other a B-type (see Table 2). This will help insure good pollination and fruit set.

Avocado varieties are classified in three groups, known as the West Indian, Guatemalan and Mexican “races”. West Indian avocados come from the tropical lowlands of southern Mexico and Central America. Guatemalan and Mexican avocados, on the other hand, come from the mid-altitude highlands of Guatemala and Mexico. The distinguishing characteristics of the three races is summarized in Table 1. Most of the early season varieties in Florida are West Indian types. The midseason and late season varieties are mostly Guatemalan-West Indian hybrids or Guatemalan types, which have traits that are in between those of the two races. Some characteristics of Florida avocado varieties are summarized in Table 2.

West Indian and some hybrid varieties do best in lowland tropical climates and subtropical areas that don’t get too cold. Mexican varieties are more cold-tolerant and not well-adapted to lowland tropical conditions. Guatemalan x Mexican hybrids are generally more cold-tolerant than West Indian x Guatemalan hybrid varieties.

In general, avocados should be planted in the warmest areas of the State, i. e. , along the southeast and southwest coasts of Florida. West Indian and some hybrid types can’t handle cold well and only do well in places where it doesn’t freeze very often (Table 1). Varieties with little cold-tolerance include Donnie, Dupuis, Simmonds, Pollock, Nadir, Hardee, and Waldin. Some types, like Tonnage, Taylor, Lula, Kampong, Meya, and Brookslate, can handle cold better and can be planted in places where it rarely gets below freezing (24°F–28°F). Moderately cold-tolerant types (25°F–30°F) include Beta, Choquette, Loretta, Booth 8, Hall, Monroe, and Reed. More than just able to handle low temperatures, Mexican and Mexican hybrid varieties like Brogdon, Ettinger, Gainesville, Mexicola, and Winter Mexican can really handle it. However, these varieties may be difficult to find in the nursery trade.

Most avocado varieties do not come true from seed (i. e. because a seed won’t produce the same variety, they have to be grown from stems and leaves (Figures 7 and 8). Cleft grafting is the preferred method of propagation in Florida, although veneer grafting is also used. Young, vigorously growing seedlings are used for rootstocks, and terminals of leafy shoots are used for scion material. It works best to graft from November to February or March, when it is cooler, but it can be done from June to March if there is plant material available. Cutting down trees and putting scions of the desired varieties on their stumps can be used to top-dress established trees. New shoots that grow from stumped trees can also be veneer-grafted. Propagation by cuttings and air-layering has not been successful.

In Florida, Lula and Waldin seedlings are often used as rootstocks because they are uniform, strong, and easy to get seeds for.

Less than 1% of the flowers on an avocado tree ultimately produce fruit. Some types produce a lot of fruit, but most of them fall off in the early summer. Other types produce less fruit, but most of them stay on the tree until they are fully grown. Varieties differ in productivity and in regularity of bearing, some producing a large crop only every other year. Trees that are under a good cultural program (i. e. , fertilized and watered) have less of a tendency to alternately bear.

Grafted trees begin to produce after 3 to 4 years. In Florida, fully grown trees produce about 2 to 3 bushels (110 to 165 lbs; 50 to 75 kg) of fruit each year. However, with good management, considerably better production can be expected. Avocado varieties in Florida mature from June to March (Table 2). Planting more than one variety will prolong the avocado season from the home landscape.

Planting distances depend on soil type and fertility, current technology, and expertise of the homeowner. Avocado trees in the home landscape should be planted 23 to 30 feet or more (7. 0 to 9. 1 m) away from buildings and other trees. If you plant trees too close to other trees or buildings, they might not grow right or produce a lot of fruit because they will be shaded.

Avocado trees can’t grow in soils that flood or don’t drain well, but they can handle many types of well-drained soils. When it rains or floods all the time, trees often lose growth and yield, show signs of nutrient deficiency, die back, and even die. Under these conditions, trees are highly susceptible to root infection by Phytophthora fungi.

If the sandy and limestone soils of Florida don’t flood or have bad drainage, trees grow well and produce good crops. In the home landscape, select an area that does not flood. If you think the soil might get too wet or flooded, plant on a big hill or mound made of native soil that is 2 to 4 feet high. 6 to 1. 2 m) by 4 to 6 ft diameter (1. 2 to 1. 8 m).

Care of Avocado Trees in the Home Landscape

To help avocado trees grow and produce fruit regularly, they should be fertilized and watered on a regular basis and pests, diseases, and weeds should be removed as needed (Table 3).

In Florida, young trees should be fertilized every one to two months for the first year. Start with 1/4 lb (114 g) of fertilizer per tree and work your way up to 1 lb (455 g) per tree (Table 4) After that, three or four applications a year in amounts that match the tree’s growing size are enough, but no more than 20 pounds per tree per year.

Fertilizer mixes with 6% to 10% nitrogen, 6% to 10% available phosphorus pentoxide, 6% to 10% potash, and 4% to 6% magnesium work well for young trees. For trees that bear fruit, the amount of potash should go up to 9% to 15% and the amount of available phosphoric acid should go down to 2% to 4%. Fertilizer mixes like 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)] are easy to find.

For the first four to five years, trees should get three to four sprays of copper, zinc, manganese, and boron every year, from spring to summer. Thereafter, only zinc, manganese, and possibly boron applications are necessary. Avocado trees are susceptible to iron deficiency under alkaline and high pH soil conditions. Iron deficiency can be avoided or fixed by adding iron chelates to the soil on a regular basis in the late spring and summer. These chelates are made for alkaline and high pH soils (Table 4).

When avocado trees are first planted, they should be watered once a day for the first week or so. After that, they should be watered once or twice a week for the first couple of months. During prolonged dry periods (e. g. , five or more days with little to no rain) should water their avocado trees well twice a week for the first three years after they are planted. Once the rainy season arrives, irrigation frequency may be reduced or stopped.

If avocado trees are at least 4 years old, watering them will help them grow and produce more when it’s dry for a long time. The specific water requirements for mature trees have not been determined. But, like with other tree crops, the time between blooming and fruit development is important. During this time, drought stress should be avoided by watering the plant every so often.

Many insect pests attack avocados, but they seldom limit fruit production significantly. Insect infestations are not predictable and control measures are justified only when large populations occur. Currently, the most important insect pests in Florida are:

• Avocado Looper (Epimecis detexta )
• Pyriform Scale (Protopulvinaria pyriformis )
• Dictyospermum Scale (Chrysomphalus dictyospermi )
• Avocado Red Mites (Oligonychus yothersi )
• Borers (e.g., Ambrosia beetles, Xylosandrus sp.)
• Avocado Lace Bugs (Acysta perseae )
• Red-banded Thrips (Selenothrips rubrocinctus ) (Figure 9)

Homeowners should contact their local UF/IFAS Extension office for recommended control measures.

Disease control for avocado trees in the home landscape is usually not warranted. The easiest way to keep diseases away is to plant scab-resistant varieties, make sure the soil doesn’t stay soggy, and keep an eye on the tree (especially the leaves and fruit) all year long.

To effectively control foliar and fruit diseases caused by fungi, the fungicide must be applied to all parts of the plant that are likely to get sick before the disease starts. Sprays that are used after infection (which usually happens a few days before the disease shows up) don’t always help the disease get worse. Sprays need to be used again and again as new tissues show through from growth and as spray residues get worn down by the elements. A successful program depends on:

• use of the right amount of a fungicide and an adjuvant, if needed
• Timely applications before infection is most likely to occur.
• Thorough coverage of susceptible parts.

Homeowners should contact their local UF/IFAS Extension office for current control recommendations for the diseases discussed below.

Cercospora spot (Cercospora purpurea). Infection appears on fruits and leaves as small, angular, dark brown spots which coalesce to form irregular patches. These spots have a yellow halo. Fruit lesions are frequently the point of entry for other decay organisms, such as the anthracnose fungus. Infection usually occurs during the summer months. If you have a problem with Cercospora spot, start a spraying program to stop it around May 1st and keep it up until harvest.

Avocado scab (Sphaceloma perseae). The scab fungus readily infects young, succulent tissues of leaves, twigs and fruit. These tissues become resistant as they mature. Lesions appear as small, dark spots visible on both sides of the leaves. Spots on leaf veins, petioles and twigs are slightly raised, and oval to elongated. Severe infections distort and stunt leaves. Spots on fruits are dark, oval, and raised. Over time, they join together to form cracked and corky areas that hurt the fruit’s appearance but not its quality (Figure 10). Begin a spray program for scab prevention when bloom buds begin to swell and continue spraying until harvest. Many avocado varieties are resistant or moderately resistant to scab and no control is necessary. Some varieties, like Lula, are very likely to get scab, so you shouldn’t plant them in your yard.

Anthracnose (Colletotrichum gloeosporoides). Anthracnose infection is important only on fruits. Infections occur through lesions caused by other organisms such as scab and Cercospora spot, or mechanical injuries. The fungus does not develop in actively growing fruits but causes a rot as the fruit ripens. Fruit lesions start as circular brown to black spots which enlarge, become sunken and crack.

Avocado root rot (Phytophthora cinnamomi ). This fungus is likely to harm trees in places where the soil doesn’t drain well or where it floods often. This is the most serious disease in most avocado producing areas of the world. Even though the fungus is found on a lot of trees in Florida, the disease only seems to be dangerous when the trees are flooded. Trees with the disease may have leaves that are pale green, wilted, or dead, and in the later stages, the ends of the branches die back. Feeder roots become darkened and decayed, and severely affected trees usually die.

Powdery mildew (Oidium sp. ). Powdery mildew covers undersides of leaves with a white powdery growth. Later, the white mildew disappears leaving dark, reticulate markings, which appear from the upper side as yellowish areas. Usually not serious enough to require control measures, this disease is most prevalent during the dry season.

Sun-blotch (Caused by a viroid). Infection is shown by twigs, leaves, and fruit that are sunken and have yellow or white streaks or spots on them (Figure 11). It is transmitted through buds, seeds, and root-grafting of infected trees. There is no control for this disease, and infected trees should be destroyed. This disease is rare in Florida.

Algal Leaf Spot (Cephaleuros sp. ). Symptoms appear first on upper leaf surfaces as green, yellowish-green, or rust-colored, roughly circular spots. This disease is most prevalent during summer and fall months.

Diplodia Stem-end Rot (Diplodia sp. ). This rot disease begins at the stem end of the fruit and develops as the fruit softens. It usually only happens with fruit that isn’t fully developed after it’s been picked, and it can be avoided by only picking fruit that is fully developed.

Planting in Rockland Soil

In many parts of Miami-Dade County, the soil is very thin, and there is hard calcareous bedrock a few inches below the surface. Remove a 3 to 10 ft diameter ring of grass sod. Dig a hole three to four times as wide and three times as deep as the avocado tree’s box. The different ways to dig a hole are to break up the rock with a pick or a digging bar, hire a company with augering tools, or use a backhoe. Plant as directed in the proceeding section for sandy soil.

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