Avocado trees most likely originated in Southern Mexico and were cultivated for centuries before North America was colonized. The pear-shaped fruits are a delicious, rich food that make an excellent condiment or eat alone addition to your diet. The trees are warm season plants, easily damaged by cold and frost. That said, northern gardeners must learn how to grow an avocado houseplant in order to enjoy fruits grown at home.
Hass avocado trees (Persea americana “Hass”) produce the purplish, pebble-skinned avocadoes found in supermarkets. In a grove, the tree grows up to 60 feet high in well-drained soil with a pH between 6.0 and 6.5, and produces dark green, shiny leaves and small greenish flowers. With pruning, it can grow in a container, but will bear less fruit. Hardy in U.S. Department of Agriculture plant hardiness zones 8 through 11, it tolerates temperatures as low as 26 degrees Fahrenheit. Grow a tree from a grafted seedling rather than from a seed to preserve the cultivar characteristics and obtain fruit in three years.
Purchase a grafted Hass avocado seedling from a nursery. Look for a healthy seedling with glossy, dark green leaves and without wounds or signs of insect infestation, such as webbing or discoloration.
Choose a half-barrel container or other 24-inch wide and 18-inch deep wood or clay container with drainage holes, and place the container in a sunny location. Partially fill the container with potting mix and plant the Hass avocado seedling in the soil at the same depth as it was growing in the original container. Cover the roots with potting mix and water deeply until the water flows through the drainage holes.
Water the Hass avocado lightly when the soil surface feels dry to the touch, and avoid over watering, which can cause root rot. Fertilize with 1/4 teaspoon of balanced fertilizer every three months after the first year of growth.
Monitor the leaves for tip burn, and the soil and container for white crust, which indicate excess salt accumulation. Flush salts from the soil by watering the soil and letting the water flow through the drainage hole for a few minutes.
Inspect Hass avocado leaves regularly for purplish or brown discoloration, which is a symptom of six-spotted spider mite infestation. Provide the tree with proper growing conditions and allow predatory mites, ladybugs and other natural predators to control the mite population. Spray narrow-range horticultural oil to heavily infested plants, as recommended by the University of California Integrated Pest Management Program.
Check your Hass avocado plant for yellow or dropping leaves, which are symptoms of Phytoph thora root rot. Allow waterlogged soil to dry out before you water a plant that has root rot symptoms.
Harvest Hass avocado fruits two to three years after planting, and 12 to 18 months after the flowers bloom. Allow the skin to turn purple before you pick the fruit, and do not wait for the fruit to ripen on the tree. If the fruit remains on the tree, it will grow larger but will not ripen.
Prune upper branches back to the crotch after harvest only when necessary to maintain the desired height. Remove branches or twigs that die back as the Hass avocado tree tries to outgrow its limited root system.