Avocado

About this plant. Avocado is a tropical evergreen tree native to Central America, with glossy leaves and small greenish-yellow flowers. Outdoors it can grow very tall, though commercial trees are often kept shorter. Some references describe it as a bushy evergreen shrub or small tree. The fruit has rich, fatty, edible flesh, eaten raw, spread on sandwiches, in desserts, or as guacamole.

Sowing from seed. Seed-grown avocados are usually started as houseplants, and the seed germinates quickly and easily. Wash the seed after removing it from the fruit, then push three or four toothpicks into its sides about halfway up. Suspend it in a glass of water with the broad end down, so the bottom quarter sits in the water. Top up the water as it drops. Roots usually appear first, and the seed should sprout within a few weeks; if it does not sprout within 2 months, start over with another seed.

Potting. When the seed splits and roots appear, which takes 2 to 6 weeks, it is ready to transplant. Pot it once the roots are 2 to 3 inches (5 to 8 cm) long. Use a 6- to 8-inch (15 to 20 cm) pot of commercial potting mix, with the top of the seed level with the soil surface.

Alternative method. Another method soaks the seed in hot water at 104 to 125 °F (40 to 52 °C) for 30 minutes, cuts a thin slice from the pointed end, and sows it in moist sandy compost with the cut end slightly above the soil surface. Keep it at 68 to 77 °F (20 to 25 °C) while it sprouts.

Commercial plants. Trees grown for fruit are typically grafted or planted on rootstock, and named cultivars are propagated by grafting.

Light. Full sun is best, and the plant tolerates some light shade. Indoors, a bright spot near an east or west window works well.

Watering. Keep the soil moist but not wet.

Feeding. Fertilize once or twice a month in spring and summer with a dilute fertilizer. Another guide suggests a balanced liquid feed every 2 to 3 weeks.

Temperature and pinching. Avocado will not tolerate frost. Grow it under cover in a container at least 12 inches (30 cm) across, and keep temperatures at 68 to 82 °F (20 to 28 °C) with high humidity. To encourage branching, pinch out the growing point when the seedling is 12 to 15 inches (30 to 38 cm) tall.

Diseases. Laurel wilt threatens commercially grown avocados, and infected trees often die within 4 to 8 weeks. Plants can also develop fungal leaf spots and Phytophthora root rot. Houseplants can get root rot if the soil stays too wet.

Pests. Whiteflies, thrips, red spider mites and mealybugs may be a problem.

Fruit and time to bearing. Different varieties have different harvest times in spring and summer. Gardening experts profile lists a time to maturity of 10 to 20 years. A houseplant grown from seed will not produce fruit, so you shouldn’t expect any avocados from it.

Varieties. There are three common commercial types. Mexican types are the hardiest and have the highest oil content, Guatemalan types are less hardy with medium oil, and West Indian types are fully tropical with the lowest oil content.

Horses are listed as a problem for this plant. The leaves are toxic if pet rabbits eat them, and the fruit is harmful to caged birds if they eat it repeatedly. These warnings are for pets only, and no cat or dog toxicity information is given here.