Origin
Persea americana or ‘Avocado’ trees are native to North and South America where they grow in warm, humid climate zones. They are very sensitive to frosts and heavy winds, therefore are not commonly grown outdoors in cooler climate zones. It is thought that the fruits the tree produces have been consumed by people for close to 10,000 years and domesticated about 5,000 years ago. However, the fruits were not as appetizing 10,000 years ago as they are today. Since domestication 5,000 years ago, the fruit’s size and flavor has improved through seed selection and breeding to create the Avocado tree varieties we now consume.
Growth
Avocado trees are a very popular tree to grow in warm, sunny climates because of the reward of the highly nutritious fruit they produce after a few years of growth. These ‘fruits’ are actually large, savory berries. Given the right growing conditions and depending on the cultivar, avocado trees can grow to be about 60 feet high and 30 feet wide. However, they will grow to be much smaller trees when grown in pots or indoors.
At some point you may have experimented with growing an avocado tree from a seed saved from a store bought avocado. This is a fun way to propagate an avocado tree, but if you want to grow an avocado tree for its fruit, it is best to buy a tree from a nursery that has been grafted onto a root stock that will ensure the fruit is good quality. Avocado trees don’t grow true from seed. This means that a tree grown from seed will not be the same cultivar as the tree the fruit came from.
Depending on the variety, Avocado trees typically begin producing fruit anywhere between three and five years given the tree is grown in the right conditions. Avocado trees do best when grown in plant hardiness zones 9-11. If you are unsure of your hardiness zone, you can find it out through the USDA Plant Hardiness Zone Map. Avocado trees require six to eight hours of direct sunlight a day with temperatures between 60°-80° F and consistent watering.
Avocado trees are self-fertile meaning they have both male and female flower parts and can pollinate themselves. The tricky part is that the male and female flower parts open at different times, so self-pollination is inconsistent. Having multiple avocado trees can increase the likelihood of pollination resulting in higher fruit yield. For the most successful fruit yield, purchase a type A and a type B tree. These two different types of avocado trees open their male and female flower parts at the same time therefore increasing the likelihood of pollination. Two of the most popular Avocado cultivars are ‘Haas’ and ‘Fuerte’. ‘Haas’ avocados are a type A variety and ‘Fuerte’ are a type B variety, so they are compatible cultivars to grow together.
Planting
Whether you are planting your Avocado tree straight into the ground or in a pot, it is important that the soil is well draining. If your ground soil is clay-like or sandy, it should be amended with garden soil or compost before planting. The planting hole should be dug deep enough so the roots are about two inches below the soil line. If the root ball is buried too deep below the soil line, the roots can suffocate and therefore should be right below the soil line. Ensure there are about six inches of space around the root ball so the roots have space to grow into. Fill the space with garden soil.
Since Avocado trees need six to eight hours of sunlight per day, it is best to plant them on the south side of the yard. If you are planting multiple Avocado trees, ensure they are spaced at least thirty feet apart so the canopies have space between each other when they mature.
If you are planting your Avocado tree in a pot, ensure the pot is twice the size of your tree’s root ball. It is best that the pot is made of a porous material such as clay or ceramic to absorb any excess moisture and to insulate the roots from heat and cold. Plastic pots should be avoided. Container grown Avocado trees should also be placed on the south side of the yard or in front of a south facing window if grown indoors.
Applying a thick layer of mulch around the base of the tree after planting will help protect the tree’s sensitive roots and prevent moisture loss and soil degradation. Space the mulch one foot from the trunk to allow the roots to breathe through the soil.
Watering
Avocado trees need consistent water to grow healthily, especially when they are newly planted. When being grown in a pot or in the ground, an Avocado tree’s soil should be kept evenly moist at all times. Avoid letting the soil go completely dry between waterings to prevent drooping and leaf loss. Soil that is kept saturated and does not get a chance to mostly dry between waterings can cause the tree’s roots to rot. Signs of excess moisture are yellowing leaves, leaf loss and blackening stems.
The watering schedule for your avocado tree can fluctuate based on the season and the age of the tree, but each watering should be deep to ensure the entire root system gets moisture. Watering should be done more frequently during the hot, summer months and less frequently during spring, fall and winter or when rain is in the forecast. A general watering schedule for an in-ground tree is once or twice a week during the summer, every two weeks during the spring and fall and once a month during the winter.
Fertilizing
As Avocado trees mature into fruit bearing size, they should be fertilized regularly for strong growth and fruit production. Avoid fertilizing an Avocado tree that is less than a year old as they have sensitive roots that can be damaged by fertilizers when young. Compost or manure mixed into your tree’s soil will provide enough nutrients its first year.
Established Avocado trees over a year old should be fertilized throughout the spring and summer months with a fertilizer designed for avocados and citrus such as FoxFarm Citrus & Avocado. Avocado trees and citrus trees have the same nutrient requirements. Avoid using synthetic fertilizers as the salts in these fertilizers can burn your Avocado tree’s sensitive roots.
Along with regular fertilizing, the base of your Avocado tree should be top dressed with a layer of compost or manure to continue building a better soil structure while naturally feeding your tree and keeping the pH in the right range. Avocado trees prefer their soil to be slightly acidic with an ideal range between 6.0 and 6.5. If your soil is too alkaline (above 7.0), the tree’s roots won’t be able to properly absorb nutrients. A pH testing kit can be used to determine the pH of your soil throughout the year.
Some of the most common nutrients Avocado trees become deficient in are zinc, iron and nitrogen. Zinc and iron deficiencies will show symptoms in the new growth with yellow leaves and green veins. Nitrogen deficiencies begin in the older leaves and move to the new leaves with a light green or yellow appearance with yellow veins.
Pruning
Avocado trees don’t need much pruning except to shape the tree and to remove dead or diseased branches. Young trees can be trained to be a shorter, fuller tree by pruning back tall, vertical branches which will encourage more lateral branching. Pruning your tree in this way will make harvesting much easier.
Maintenance pruning can be done throughout the year to remove dead or unhealthy branches. Avocado trees that have been over-watered commonly develop black stem rot. Rotten stems should be pruned back to a healthy, green portion of the stem to prevent the rot from spreading down the trunk. The healthier the stems are on your Avocado tree, the healthier the fruit production will be.
Pests
There are a variety of pests that like Avocado trees just as much as we do. The most common pests of Avocado trees are both chewing and sucking bugs. Chewing bugs such as beetles and grasshoppers do the most significant damage by chewing up the leaves on Avocado trees. These bugs typically migrate through causing minimal damage, but if they are not controlled can defoliate an entire small tree.
Sucking insects such as scale, mealy bugs, aphids, whiteflies, thrips and mites can suck the sap out of an Avocado tree’s leaves creating dead spots and eventual leaf loss. Sucking insects are the hardest pests to control on Avocado trees because they can reproduce very quickly and spread throughout the other plants in your garden.
Insecticidal soaps are the best treatment for insect and bug pests on an Avocado tree. Multiple applications should be done to eliminate as much of the population as possible and to deter larger bugs from migrating to your tree.
Diseases
The most common diseases that plague Avocado trees are fungal leaf spots, powdery mildew and root rot. Fungal spores affect the leaves of the Avocado tree much like insects do by sucking the sap out of the leaves until they eventually curl and fall from the tree. Symptoms of fungal leaf spores are circular patterns on the leaves which can be orange, yellow or black in color or a thin layer of fungus either white or black in color. Fungi that attack the leaves of an Avocado tree can be treated with a copper fungicide and multiple applications may be necessary to catch all the spores. If left untreated, the fungal spores and defoliate your Avocado tree and spread to other plants throughout your garden.
Root rot is caused by an overgrowth of fungus and bacteria within the Avocado tree’s root system. Often this overgrowth is caused by excess soil moisture. Ensure you are planting your Avocado tree into a porous soil and letting the soil significantly dry out between waterings to reduce the chances of root rot. Symptoms of root rot are drooping branches, yellow leaves and blackened branches. If caught early, root rot can be treated with root drenches that add beneficial bacteria to the soil to fight off the bad bacteria. If rot has spread throughout the entire root system of your Avocado tree, it is unlikely that it can be saved.
If you have any questions about caring for an Avocado tree, one of our Plant Care Specialists will be happy to assist you through a 15 or 30 minute plant checkup which can be booked below!