Answer: Avocados are self-fertile so you need only one tree in order to have a crop. I'm not sure why your tree needs to be grafted. Here's some growing information on avacado trees:
California avocado trees are one of the most popular tropical fruit trees used in landscaping in zones 9, 10 and 11. They like soil ph of 6 to 6.5. It is a shallow rooted tree that needs good aeration and does best when mulched with coarse material such as redwood bark or other woody mulch about 2" in diameter. Use about 1/3 cubic yard per tree, but keep it about 6 to 8 inches away from the trunk. Plant in a non-lawn area with full sun, protected from wind and frost. The ideal time to plant is March through June. During summer there is risk of sun damage since young trees can't take up water very well.
The hole should be as deep as the root ball and just a bit wider. Gently place the root ball in the hole taking care not to disturb the delicate root system. If the ball is root-bound, carefully loosen up the soil around the edge and clip away any roots that are going in circles. Back fill the hole with soil. Do not use gravel or potting mix.
The major nutrients needed by avocado trees are Nitrogen, Phosphorus and Potassium (NPK) in a 7-4-2 fertilizer and Zinc. Feed young trees 1/3 to 1/2 pound of actual nitrogen per tree per year, spread out over several applications if you like.
When watering, it is best to soak the soil well, then allow it to dry out somewhat before watering again. At planting, the tree can hold about 2 gallons of water. Depending on the weather, your tree may need a gallon of water a day along the coast. Typically, trees need to be watered two to three times a week. A mature tree will take about 20 gallons of water a day.
Hope this answers all your questions!
Q&A Library Searching Tips