Most of us have tried to grow an avocado (Persea americana) tree from seed. Although an avocado plant can be grown in any large, indoor room, it’s also does well in a heated greenhouse. Both heat and humidity must be kept fairly high for an avocado tree to thrive.
To grow an avocado from seed, start by half-submerging a well-rinsed pit (pointy end up) in a container of water, with the pit supported by three toothpicks stuck into its sides. After about six weeks, the pit will split in half and a root will start growing downwards into the water. Then a stalk will start sprouting upwards.
After planting the seedling in a good-quality soil and keeping it warm and moist, the assumption is that the avocado should grow fine from here on. it often wilts and dies if not kept warm and moist. For most beginners, a gangly stalk grows straight up until it’s about four or five feet tall. This is hardly the lush, subtropical plant imagined.
The trick to producing an attractive, bushy avocado tree is to snip off the growing tip (the top two or four tiny leaves) after the plant is about 12 to 18 inches tall. This causes the stalk to produce lateral branches. By snipping off the growing tip on each branch, a plant with a nice, bushy form can be obtained, as long it receives adequate sunlight.
But don’t expect this plant to give you a bountiful crop of avocados. Avocado plants grown from seed are usually sterile, or at best they set fruit that is nothing like that of the parent plant. To get the avocados you know and love, you must graft a fruiting avocado branch onto your pit-grown tree.
To do this, let the stalk grow without snipping off its tip until it’s about two feet tall. This should produce a stalk strong enough for grafting. The branch you use for grafting should come from a propagated avocado plant. The new branch should be the same diameter as the stalk onto which it will be attached. Simply cut a v-notch in the stalk and cut the end of the branch to fit the notch. Then secure the branch in place with grafting tape or a suitable substitute. Make sure the bark on both pieces is precisely aligned to enable the flow of sap, and minerals through the vascular tissue. Now just water the plant and wait for it to grow. If the graft takes, it will start to grow, and in a few years you should get avocados. Snip off any branches that sprout below the graft because they will absorb the sap that should go to the new branch and the new branch will die.