Description & Interesting Facts:

The avocado is an evergreen tree in the laurel family (Lauraceae). It is native to the Americas and was first domesticated in Mesoamerica more than 5,000 years ago for its large and unusually oily fruit. It’s highly likely that the avocado originated in the highlands bridging south-central Mexico and Guatemala, and today the trees have a native growth range from Mexico to Costa Rica.

Avocado trees did not receive serious horticultural attention until around the 1900’s, when horticulturists found that production of grafted trees was simple and the perpetuation of superior seedlings allowed for the establishment of orchards. Today, flourishing avocado industries have developed around the world wherever the climate is suitable for growing avocados.

Avocado Races

Horticulturally, avocados are divided into races: Mexican Race (Persea americana, variety drymifolia); West Indian Race (Persea americana, variety americana); and the Guatemalan Race (Persea americana, variety guatemalensis), with more than 1,000 cultivars between them, distinguished by their origin, morphology, climatic adaptations, and fruit characteristics.

Originally, there were three avocado types used commercially for avocado production. These three races enabled cultivation in different climatic regions and extended the harvesting season.

The frost-sensitive West-Indian cultivars were developed in the hot and moist tropical lowlands of Central America. Guatemalan avocados prefer cool tropical conditions with a narrow range of temperature extremes, and Mexican avocado types are more adapted to cooler, high-lying, tropical conditions with wider temperature extremes.

From these original three races modern cultivars such as Fuerte, which is most popular in South Africa, have been developed by natural bred combinations of original avocado races. In Fuerte’s case, it’s a cross between Guatemalan and Mexican races, allowing the cultivar to be grown in climates with a wider temperature range than the pure Guatemalan type.

Depending on their race, avocado trees can be tall or spreading, and once mature can reach heights up to 18m with a 9m spread. Rather than a single, deep taproot, their fibrous, shallow root system spreads out near the soil surface, and can extend out to a remarkable diameter of 9m or more, depending on the tree's size and age. The elliptic to egg-shaped leaves vary in size from 8 to 30cm in length.

Avocado Flower Types

In South Africa, depending on the specific cultivar, avocado trees typically flower during the cooler winter months into spring (July to September). Fruit set usually commences around the end of September.

The trees will blossom profusely every year, sprouting from racemes near the leaf axils. The blooms are small and inconspicuous with no petals, but rather two whorls of three pale-green or greenish-yellow, downy lobes. Each blossom has 9 stamens with 2 basal orange nectar glands.

Interestingly, there are two types of avocado flowers: ‘Type A’ and ‘Type B’, depending on the flowers’ opening time. These flowers are dichogamous, meaning that the male and female parts mature separately, and each flower opens only twice.

‘Type A Flowers’ are functionally female in the morning, closing at midday. When they reopen the following afternoon they function as a male.

‘Type B Flowers’ are functionally female in the afternoon, closing in the evening, and reopening the following morning as functionally male.

When A and B flower types are grown together, this temporal overlap of mature male and female parts encourages cross-pollination and greater fruit production.

Avocado trees are partly self-pollinating, but yields are higher when A and B types are combined. To maintain consistent fruit output the trees are often propagated through grafting.

Avocado Fruit:

The fruit, sometimes also referred to as an “alligator pear” or “avocado pear” is botanically a large berry containing a single large seed.

The shape and size of the fruit is exceedingly variable in size between the various avocado races, varying from round to egg and pear-shaped, with a long slender neck. Fruits in certain Mexican races are no larger than a hen’s egg, and in other races they can weigh up to 1kg. The fruit’s outer skin is sometimes no thicker than that of an apple, or thicker, coarser, and woody in texture.

Selective breeding by humans has resulted in various cultivars with larger, fleshier fruits with a thinner skin. Depending on the cultivar, modern avocados have green, brown, purplish, or black skin, and may be pear-shaped, egg-shaped, or spherical. The fruit of these domestic varieties have smooth and buttery, golden-green flesh when ripe.

The large central seed can vary in size from 5 to 6.4cm long. Early wild avocados prior to domestication had much smaller seeds around 2.1 to 2.2cm in diameter, likely corresponding to smaller fruit size.

When are Avocados harvested in South Africa?

Avocado harvesting season in South Africa extends from February to November, with the most significant harvest occurring from March to September.

The actual harvest time can vary depending on factors like the specific cultivar, weather conditions, and the location within South Africa.

Depending on the production area, and whether the cultivar is an early or late-season variety, harvesting in South Africa starts in February with the early season ‘Fuerte’ and ends in October and November with ‘Hass’ and ‘Ryan’.

New varieties are continually being developed and planted to extend the avocado harvest.

A healthy avocado tree can produce upwards of 200 avocados per season. For grafted, nursery-bought trees, you can expect to see fruit in three to four years. However, avocados started from seed may take anything from 5 to 15 years before fruits appear.

Where are Avocados cultivated commercially?

Avocados are presently cultivated in the tropical and Mediterranean climates of many countries. Mexico, the Dominican Republic, Peru, Indonesia and Colombia are top producers worldwide, and the fruits are also grown commercially in Florida, California, Hawaii, Kenya, Haiti, Chile, Brazil, Australia, and South Africa, as well as on some Pacific islands. Avocado cultivation is expanding into the Mediterranean region, including Israel, areas like the Iberian Peninsula, Southern Europe, and even specific locations in Greece, Spain, and Italy are becoming important growing regions.  

Avocado production in South Africa has traditionally been concentrated in the warm subtropical areas of Limpopo and Mpumalanga. However, production is expanding in KwaZulu-Natal and the Eastern and Western Cape provinces.

Avocado cultivars for South African gardens

Avocado Fuerte

Fuerte is well-known and loved in South Africa for its creamy texture and rich buttery flavour with notes of hazelnut. It produces medium sized, pear-shaped fruits with a long neck and a relatively smooth, and medium-thin, dark green skin when ripe. The skin has a bumpy yet smooth and pliable texture, not adhering well to the flesh, allowing it to peel easily. Therefore, careful handling once picked is essential. This variety is primarily valued for its culinary use, especially when eaten raw. It is also popular for making avocado oil.

Fuerte tends to grow tall, between 7 to 10m, but can be pruned to keep it shorter for easier harvesting.

Fuerte is a ‘Type B’ avocado which is self-pollinating, but if planted  with a ‘Type A’ avocado like ‘Hass’ yields will be better.

In South Africa, Fuerte is harvested early in the season, typically starting in February and continuing through April, particularly in the far north of the Limpopo province around the town of Levubu.  

Cross-pollination permits the development of unlimited varieties, which is the case with Fuerte because it is a mix of Mexican and Guatemalan avocados. The name "Fuerte," meaning "strong" or "hardy" in Spanish was given to this variety due to its vigorous growth, and its tolerance of colder temperatures than other varieties.

Avocado Hass

Hass is one of the most popular avocado varieties worldwide, and with its rich creamy flesh and superior taste, one of the most delicious. The smallish fruits are round to egg-shaped, and unlike other avocados with their smooth green skin, Hass has dark green bumpy skin that darkens as the fruit ripens; eventually reaching a very dark shade that is almost black. Hass trees have high yields compared to other varieties and a mature tree can produce over a million blooms.

Harvesting in South Africa typically occurs from late May to October, with some regions like the Western Cape having a later harvest period, starting in late September or October and even continuing until December.

The trees grow around 10m tall, but can comfortably be kept 4 to 5m with regular pruning.

Hass is a Pollination ‘Type A’ tree and can self-pollinate. It is known to produce a reasonably sized yield when grown on its own, but partnering it with a 'Type B' variety will increase pollination opportunities and provide greater yields.‘Edranol’ and ‘Fuerte’ make very good pollinators to grow with ‘Hass’.

Hass is more sensitive to heat than other varieties.

Avocado Pinkerton

The Pinkerton avocado is a popular cultivar known for its medium to large pear-shaped fruits with an elongated neck. The yellow-green flesh has high oil content, with a mildly earthy aroma and hints of nuttiness. It has a fine, smooth and creamy texture that’s not at all fibrous, and not as rich as other varieties like Hass.  The green, slightly pebbled skin is leathery in texture and easy to peel.

Pinkerton is believed to be a hybrid of ‘Rincon’ and ‘Hass’ avocados, and has gained attention due to its high fruit-to-seed ratio, its early seasonal availability, high yields, and also because it is a conveniently smaller sized tree, growing around 7m tall and spreading 6 to 9m. Regular pruning will keep it a lot smaller.

Look out for dwarf varieties that only grow about 2 to 5 meters tall, making them suitable for smaller gardens and large containers.

Pinkerton avocados are typically harvested in South Africa from April to July. This period can vary slightly depending on local weather conditions.

Pinkerton avocados are identified as a ‘Type A’ variety of Guatemalan descent, though they were first cultivated in California. Although self-pollinating, Pinkerton is more reliant on having a cross-pollinator, which means it should be planted with a ‘Type B’ variety like ‘Fuerte’ or ‘Edranol’ for good fruit set.

Pinkerton avocados are also noted for their relatively good cold tolerance and are often grown in mild winter regions.

Avocado Edranol

Edranol is a sought-after variety known for its rich, nutty flavour and buttery, smooth flesh. It is a medium to large, oval to pear-shaped avocado with slightly pebbled dark green skin with corky lenticels.

Edranol is typically harvested in South Africa from June to September. The season starts earlier in Limpopo & Mpumalanga running from June to July, and starts later in KwaZulu-Natal, extending into late September.

The tree can grow around 10 metres tall, but can be comfortably kept to 4 to 5 metres with regular pruning.

Endranol is a ‘Type B’ avocado, and although self-pollinating, yields are more dependable when it is partnered with ‘Type A’ trees like ‘Hass’ or ‘Pinkerton’.

Avocado Ryan

The Ryan avocado is generally a medium to large size with an oval, egg-shape. It resembles Hass, but remains green on ripening. The skin is relatively thick, tough, and textured, and covered in raised pebble-like bumps.

The flesh is primarily yellow-green, with a thin, darker green ring below the skin. It is dense, creamy and smooth, with a mild, subtly sweet and earthy flavour. Ryan is a Mexican x Guatemalan hybrid variety with characteristically firm flesh, lending it to dishes where the flesh retains its shape. Therefore, it is suited for both fresh and cooked preparations.

Late-maturing Ryan trees are heavy bearers. In Limpopo the fruit ripens in August and September and in October in KwaZulu-Natal.

Ryan is a ‘Type B’ avocado and does best if cross pollinated with a ‘Type A’ avocado like ‘Hass’ or ‘Pinkerton’ to improve yields.

Ryan avocado trees can grow to between 6 and 12m tall, but can be pruned to keep the tree within bounds.

The trees are reasonably cold resistant.

Avocado 'Hass'In the Garden:

Though the fruit may be the main draw for many growers, avocado trees are also quite beautiful with their thick, bright green foliage and magnificent stature, adding ornamental value to large outdoor spaces.

Avocados can even be grown in large pots outdoors, though it will stifle their growth. Luckily breeders have been hard at work, and today dwarf varieties are becoming more freely available, and these are great in small gardens and pots.  Dwarf potted trees have an added advantage in that they can easily be covered or moved to sheltered positions in colder winter regions.

Health Benefits:

Although avocados have a high fat content they can be part of a successful weight management programme because the monounsaturated oil they contain is believed to speed up the body’s metabolic rate.

They are also rich sources of vitamins such as A, B6, E and C and minerals such as potassium and magnesium.

In the Kitchen:

The nutrient density and high fat content of avocado flesh has advantages for various cuisines, including vegetarian diets.
Avocados are glorious eaten straight out of the skin with a spoon, and their creamy, gentle nutty flavour makes them perfect for mixing with the robust flavours of chillies, peppers, coriander and lemon.

Mashed avocado is the principal ingredient of guacamole, and avocado trees are sometimes called “guacamole trees” after this dish that originated in Mexico.

Avocados are now used in just about every country in the world, in both sweet and savoury dishes - to flavour liquors, in Japanese sushi, and in Indonesia the flesh is even made into a milkshake.

There is a whole world of avocado recipes out there online, so search for your favourites and enjoy!

Avocado 'Fuerte' Cultivation:

Pollination

Avocado trees require transfer of pollen from one flower to another for pollination to occur, which is best done by bees. Some cultivars require the pollen of another cultivar for fertilisation to take place, but cultivars such as Fuerte and Hass are self-compatible, and can be pollinated from the same cultivar.

For the best pollination, it is ideal to have at least two trees. Avocado trees are considered either Flower Type A or type B, and each type opens its flowers parts at different times of day. These different times make cross-pollination between the two types possible.

Therefore, for the best results when choosing which trees to plant ensure you have both type A and type B. 

What climate is best for growing Avocado trees?

Avocado trees thrive in warm and moist tropical and subtropical regions. The Mediterranean climate's mild winters and warm, dry summers also provide a favourable environment for avocado growth, provided the trees can be irrigated in summer. Water scarcity and salinity can be issues limiting yields in Mediterranean regions, requiring careful irrigation practices.

The ideal temperature range for avocado cultivation is between 15°C and 30°C.

Are Avocado trees hardy to cold and frost?

Although the trees should be able to withstand an occasional, very brief freeze, generally they are frost-sensitive.  Prolonged temperatures of -1°C or lower will be too cold for most avocado trees.

The Fuerte cultivar has a wider climate tolerance and can survive temperatures of -4°C, but it will not tolerate frost when flowering.

In colder regions it is best to keep the trees in pots which can be moved to an area protected from cold weather. Dwarf cultivars are now emerging on the market, and these are great to grow in pots which are easily moved or covered in winter.

How much sunlight do Avocado trees require?

These tropical trees thrive in plenty of sunshine, so plant in a location which receives at least eight hours of sunlight per day. The trees will tolerate some light shade but produce more fruits when kept in full sun.

Avocado trees are vulnerable to high winds

Try to select a planting location that offers wind protection. On more windy sites immature trees will benefit from support.

Are the roots of Avocado trees invasive?

Avocados are not particularly destructive as far as tree roots go, but keeping any large tree as far as possible from all concrete and masonry is always wise.

Avocado trees have a fibrous, shallow root system. This means they have many thin roots that spread out near the surface of the soil, rather than a single, deep taproot. Most of the roots are concentrated in the top 15 to 20cm of soil. Depending on the tree's size and age its roots can extend out to a remarkable diameter of 9m or more.

Therefore, all avocado trees should be planted at least 7 to 10m away from structures and other trees.

What soil type do Avocado trees require?

Avocado trees prefer rich, loamy, and well-draining soil. A soil pH that is acidic to neutral, between 5 and 7, is ideal. These trees are sensitive to alkaline soil.

If the soil does not drain well, amend it with sand or another well-draining substrate before planting.

How to plant an Avocado tree

The root system of avocado trees is sensitive so try not to disturb the roots during planting.

Plant your avocado trees in square, not round holes. The size of the holes will depend on the quality of the soil. In good soil prepare planting holes around 50cm deep and 75cm wide. In poor soil (clay-rich or gritty) dig holes 50cm deep and 1m wide.

When planting your Avocado tree amend the soil with a decent amount of compost or kraal manure to provide the tree with enough nutrients to start off with. Do not fertilise a young tree.

Place the bagged tree into the hole to ensure that it will not be planted too deep. Add or remove soil until the planting depth is correct.

Cut the plant bag off and carefully remove the tree, trying to disturb the roots as little as possible.

If you wish to stake your tree, plant the stake at the same time as you plant to ensure you do not damage the roots.

Fill in and compact the soil around the roots keeping the tree planted at the same level as before.

If you want to make a dam/pond around the plant to hold water, ensure that the soil drains well as avocado trees dislike standing in water for long. Or you could make sure that when the tree is planted it is slightly raised on a mound, to prevent stem rot.

Water thoroughly, ensuring that the water drains easily through the soil.

Cover the surface with coarse mulch to retain moisture, keeping it at least 15cm away from the tree stems.

How much water do Avocado trees require?

Young trees should be watered regularly until they are established. Depending on the weather, two to three times a week should suffice.

Avocados are quite thirsty trees, and all the water that’s needed to grow them is one reason why the fruit is quite expensive. For commercial production the trees are grown in regions which receive around 1,000mm of rainfall annually, and no less than 400mm. Water scarcity and salinity can be issues limiting yields in Mediterranean regions, requiring careful irrigation practices.

Mature trees should receive around 5cm of water per week.  In regions with an annual rainfall of less than 1,000mm annually avocado trees will need supplemental irrigation, and especially during flowering time.

The trees benefit from infrequent, deep watering as this encourages deeper, stronger root growth. During hot and dry summers, the trees may require even more frequent watering. Wait until the soil begins to dry out, then water deeply.

Although the trees require regular watering, their very sensitive root system will rot if there is too much water in the soil, so it’s vital to have soil that drains well.

Their shallow roots also make avocado trees more vulnerable to droughts and hot, dry conditions cause the flowers and fruit to drop, resulting in lower yields.

Mulch

Adding a layer of mulch around the tree can help the soil retain the right amount of moisture, and will offer protection to the tree's shallow root system. Don't mulch any closer than 15cm from the trunk.

How to fertilise Avocado trees

Do not apply any fertiliser in the first year of growth, rather wait until the trees are established and are growing vigorously.

During the second year and yearly thereafter feed your trees in July, December and April, giving each tree a good helping of kraal manure, and applying a fruit fertiliser like 3:1:5, or fertilisers specifically designed for avocado or citrus trees.

Fertilisers and mulch must be kept away from the stem of the tree to avoid collar rot.

Do Avocado trees require pruning?

Young avocado trees do not need to be pruned or thinned out, except to remove dead or unwanted branches. As some cultivars grow very tall it may be necessary to cut off the tops of the main branches of young trees to encourage the tree to branch out instead, and make the fruit more accessible.

Mature trees require occasional pruning. Light pruning can be done any time of year, though heavy pruning should be done in the early spring.

Prune thick areas to ensure adequate light and airflow. Cut back any dead wood and trim away V-shaped branches. Don't take off more than one-third of the length of each branch.

Harvesting:

Individual avocadoes only ripen fully after they are removed from the tree, so for commercial purposes the fruits are picked while unripe and are ripened after harvesting.

At home, to check if they are ready, pick a few of the biggest, best shaped specimens and keep them indoors. If, after 8 to 10 days, they do not shrivel up and are soft and edible you can begin harvesting.

Don't pick all of your avocados at once. If you pick a few at a time, you will be able to extend your harvest and enjoy the fruits of your labour for longer.

Avocado 'Ryan'Propagating Avocado Trees

Growing an avocado tree from a pip suspended over a container of water is fun, but trees grown this way can take from 5 to 15 years to produce fruit, as opposed to grafted trees which take about two years. Trees grown from pips, however, make lovely indoor container plants if placed in good light.

For fruit it is best to buy grafted trees from nurseries. If you are determined to grow at least one tree from seed try to obtain a seed from an old avocado tree that was itself grown from seed.

Propagation is primarily done through grafting, layering, or cuttings. Grafting is often done to combine the desirable qualities of two different varieties of avocados, while layering and starting cuttings are done to produce duplicate trees.

Cuttings:

You will need sharp cutters, moist and well-draining potting or seedling soil, a small pot, and a rooting hormone.

In the spring, select new growth that is five to six inches long and has several leaves that have not opened.

Cut the branch at a 45-degree angle.

Wound the cut end by scraping at the bark on either side of the cutting. This will encourage root production.

Dip the cutting into rooting hormone.

Bury the cut end into moist, well-draining soil.

Keep the soil moist and place the cutting in a warm, well-lit area.

After a couple of weeks, gently tug the cutting to check for resistance, which indicates root growth.

Repot the cutting into a larger pot to grow-on.

Air Layering an Avocado tree

You will need a sharp knife, a rooting medium that can be wrapped around a branch, and rope or tape to secure the rooting medium around the tree. 

Select the branch you would like to take as a new tree.

Using a clean knife cut two circles around the branch to create a section of bark that can be peeled away.

Once the bark is removed, scrape the inner branch to clean the cambium away.

Wrap the exposed inner branch with rooting material, such as compost or another rooting medium in a small bag (make sure the compost is wrapping the branch, not the bag). Secure around the branch with rope or tape.

In several weeks, roots should develop. When this occurs, remove the bag, cut the branch off below the formed roots, and plant the new tree.

Grafting an Avocado tree

You will need a sharp cutter and a sharp knife, as well as something to cover the grafted area, such as grafting tape.

Follow steps one and two as if you are taking a cutting.

Remove the tip of the cutting, along with any leaves that are present.

Then, wound the tree you would like to graft onto by removing a section of bark.

Make sure the cambium of the cutting and the cambium of the tree are touching.

Secure the cutting onto the tree with grafting tape, making sure to cover the exposed areas.

In a few weeks, the grafted branch and the main tree should be fused together.

Problems, Pests & Diseases

Be alert to the presence of pests or early signs of disease and nutritional deficiencies. Prompt action is the best way to remedy any developing problems before they threaten the health of your avocado tree.

Nutritional Deficiencies

Nutritional deficiencies will show in the leaves:
Phosphor (P): Bronze young leaves.
Potassium (K): Yellow green leaves with dark veins.
Sulphur (S): Yellow new leaves
Iron (Fe): Yellow green leaves with light green veins
Boron (B): Green leaves with yellow margins and holes.
Zink (Zn): Rosette of small young leaves.
Zinc is extremely important for avocado trees. They require a high level of zinc for optimum growth, and as they are very sensitive to iron deficiency it is especially important to amend the soil with micronutrients.

Aphids

During flowering and formation of young leaves the plants are susceptible to green aphids. They feed on the sap, leaving a sticky residue and causing damage like curled leaves. These small, soft bodied green or black insects can be found clustering on new growth. To manage aphids on avocado trees, consider natural or organic options like insecticidal soap, neem oil, or attracting beneficial insects like ladybird bugs. Spray at times when pollinators like bees are least active.

Members can click here to read more about Aphids

Avocado Thrips

Avocado thrips are a major pest of avocado trees, causing significant scarring and economic losses, particularly on the fruit. Thrips develop well under cool temperatures, and numbers typically begin increasing in late winter and spring, and again in autumn. They feed on young leaves and fruit, primarily resulting in a characteristic "alligator skin" appearance on the fruit surface

Effective organic methods include biological control with beneficial insects, insecticidal soaps, and neem oil. Spinosad is also an organically acceptable insecticide. Consider applying these treatments thoroughly, especially on the undersides of leaves, and repeat applications as needed.

Avocado Brown Mite

This mite can cause leaf shedding and reduced fruit quality. Their feeding causes small coppery-red necrotic spots that eventually coalesce into larger ones, reducing significantly the photosynthetic capability of trees and plants and greatly reducing their production of nutrients. Heavy infestations can cause wilting and defoliation of the leaves, leaving the trees and fruit susceptible to sunburn.

For avocado mites, organic insecticides include neem oil which can be mixed with water and dish soap for spraying. Insecticidal soap can also be used as a spray, and introducing predatory mites can help control the mite population. Additionally, cultural practices like pruning and removing weeds can help manage the mite problem.

Members can click here to read more about Mites

Scale

Many scale species are serious crop pests. The waxy covering of some species protects them effectively against contact insecticides, which are only effective against the crawlers. However, scales often are controlled by oils, systemic pesticides or biological control agents such as ladybirds, parasitoid wasps and Coccinellid beetles. For gardeners neem oil and insecticidal soap sprays work well.

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Phytophthora Root Rot

This is a soil-borne fungus that infects many plants, including avocados. It attacks host plants, especially under moderate to warm, moist conditions, infecting the feeder root system and causing stunted growth, leaf yellowing, wilting, dieback of branches and eventual death. Young infected trees may die rapidly; older trees may survive for several years.

Purchasing disease-free, certified plants and avoiding planting where avocados previously grew, or where soil drainage is poor, are the best preventative steps you can take.

The disease is easily transported by equipment, tools and shoes from infected soils. Once a tree is infected there is little that can be done other than to reduce watering and to remove soil from around the base of the tree down to the top of the main roots and allow the crown tissue to dry out. Keep water away from the crown and trunk by only watering at the dripline.

Anthracnose

Anthracnose is a pre-harvest and a post-harvest problem that can cause serious losses. The most important symptom is fruit spotting, and brown lesions that enlarge and eventually cover large areas of the fruit’s surface. The pulp beneath the lesions becomes soft and discoloured, leaving the fruit inedible. Fruit drops prematurely.

Where leaves are infected, a brown necrotic band spreads inwards from the margin. In severe cases, this may spread to the branch. Infected flowers turn red or brown and drop off later.

Treatment for home gardeners involves a combination of preventative measures and fungicides. Key preventative measures include removing infected plant material, maintaining good sanitation, and avoiding overhead irrigation. For treatment, copper-based fungicides are recommended. Other options include neem oil and sulphur powders.

Warning

It is important to keep in mind that all parts of this tree, including the fruit, are toxic to a wide range of animals