The Hass avocado is frequently and mistakenly sold as a "Haas" avocado. The variety was named after Rudolph Hass who patented it in 1935, according to the Hass Avocado Board. Today, Hass is the variety most often consumed in the U.S. Give your Hass avocado tree full sun and plenty of room (at least 20 feet) to spread out. The best time to plant the young tree is from March to June. Hass avocado trees are hardy to U.S. Department of Agriculture hardiness zones 9a to 10b.
Conduct a soil pH test because the Hass avocado requires a pH of 6 to 6.5. Your county cooperative extension office offers reasonably priced soil analysis, and can offer suggestions on what amendments to use to adjust your soil's pH.
Aerate the soil in the planting area by digging into it to a depth of 12 inches with a gardening fork and crushing any large clumps of soil.
Add soil amendments, if necessary, to adjust your soil's pH level. Mix them into the soil to a depth of 8 inches.
Dig a planting hole the same depth and twice the width of the pot in which the Hass avocado is growing. Use the gardening fork to lightly scrape the sides of the hole to make it easier for the roots to penetrate.
Remove the Hass avocado tree from its pot and place the roots in the planting hole. Cover the roots with soil and use your fingers to gently work it around and between the tree's roots.
Fill the hole halfway with soil and then fill it with water. When the water drains, finish filling the planting hole with soil and lightly press it down around the base of the tree.
Water the newly planted Hass avocado tree until the water puddles.
Pour a 3-inch layer of mulch on the soil and, keeping it 6 inches from the trunk, spread it in a 3-foot radius around the Hass avocado tree.
Water the Hass avocado slowly and deeply. A soaker hose, set for two to three hours, should supply the necessary irrigation. Allow the soil to dry out between irrigations.
Fertilize the young Hass avocado tree once a year with 1 to 2 tsps. of a balanced fertilizer containing zinc according to package directions.