Avocados are considered one of the healthiest and tastiest fruits on the planet. Its rich, creamy inside is filled with nutrition and flavor and growing your own avocados is a fun adventure for the gardener. Avocado (Persea americana) is a native fruiting tree of Mexico and Central America. Avocado fruit varies in weight from 4 ounces to more than 5 pounds depending on variety.
In The Garden
When left on their own, avocados can grow upwards of 20' tall. Judicious pruning can restrict the height significantly and this is often done in commercial plantings for ease of harvest and spraying.
In a Container
As a container plant, the height of the avocado tree is restricted by the size of the container as well as pruning. The cycle of growth begins in winter to early spring with the expanding and opening of flower buds. In greenhouse culture in the north, this starts before the end of December and continues until late winter or early spring depending on the variety.
Flowering time is related to growing temperatures and day length. Grafted varieties flower quickly, usually the first year. These young plants, however, aren't mature enough to fruit and the flowers will fall off. This happens until the plant is large enough to bear fruit.
Fruiting an Avocado
As container plants, trees need to get to 6-8' tall with a trunk caliber of 1.5"- 2" before they will set fruit. This requires a large, 24" pot (15 to 25 gallon). It takes a few years for young grafted plants to reach this size.
Putting on Growth
Once the flowering cycle is finished, plants return to vegetative growth over the spring and summer months. Healthy plants, even in pots, can put on 2' or more on the strong upright branches. During the mid to late summer's growth, the plant will form flower buds, and although they are not visible, they swell as the fall and winter season approaches, and the cycle begins over again.
Pruning right after the flowering cycle is complete will give the least disruption to the flower bud formation. Generally, plants are headed back at this time making strategic cuts that lessen the height and width but trying not to disturb the shorter lateral braches where much of the flowers and the fruit will form.
What type of Container is Best
Terracotta containers are porous and allow the roots to have better aeration. This causes the soil to dry quicker thus reducing potential pathogens. Plastic pots can be used as long as a highly drained potting media is used. You can increase soil drainage by adding more perlite or sand to the mix.
How to Fertilize
In containers, avocados are moderate feeders. It is best to use a balanced fertilizer with a slightly elevated middle number (phosphate) like 7-9-5. Feeding can be done through irrigation. When you water, add small amounts of liquid fertilizer once a week or every two weeks. Remember the more often you fertilize container grown avocado plants, you need to reduce the amount of fertilizer that's added to the water. For example, if you fertilize every week, add 1/4 tsp per gallon or if you fertilize every two weeks, add 1/2 tsp per gallon.
Top Dress Fertilizer
Another option is to use a slow release fertilizer that is sprinkled or top dressed on the surface of the soil. These typically last for 3-6 months and release fertilizer slowly into the pot. When using slow release fertilizer, don't top dress too late in the season so the fertilizer will taper off and the plant will have time to harden off before the onset of cold weather.
Granular Organic Fertilizer
You can also use a granular organic fertilizer which, like the slow release, is sprinkled on the soil surface and allowed to leach into the potting mix. Organic fertilizers generally have a slow release component to them and so only a couple applications are needed per season.
Like any plant, avocado plants can be over fertilized. This results in excessive lush leaf growth, burned foliage, and reduces fruiting potential, as well as aggravating the root disease issue. If you have used too much fertilizer, it is important to leach the fertilizer out of the soil by watering the plant continuously until you see water flowing out the bottom of the pot. Do this for several minutes.
Sensitive Root System
One of the problems with container grown avocado plants is root rot. As is the case with most root disease, the cold damp conditions of winter often initiate the problem. Be sure to keep the plant's root system warm during cooler temperatures. Once soil disease organisms affect the root system, it is very hard to return the plant to health.
Manage Soil Moisture in Winter
When growing plants that are going to winter over in a northern greenhouse, conservatory or sunroom, where the night temperatures are below 60˙F, it's important to manage the soil moisture accurately. Bring the potting media to almost dryness, and then thoroughly soak the soil. A little wilt is better than constant soil moisture. The organisms that cause the root collapse thrive in damp cool soil and don't proliferate under dry conditions.
Pests for Potted Avocados
In northern climate culture, few insects bother the plants with the exception of mealy bugs and they are generally not much of an issue.
Insects to Look for if Avocados are Grown in the Garden
In areas where avocados are grown outside year-round, there are different pests that do affect the plants; some of which are mites, thrip and fungi. If you live in an avocado growing area, it is best to check with your local agricultural extension agent for pest problems and recommended controls in your area.