Cherimoya (Annona cherimola), also known as the custard apple, is thought, by some, to be the tastiest tropical fruit. The tree has very particular growing requirements and the fruit has a short shelf-life. Cherimoyas don't do well in arid or humid regions, or those with extreme heat or cold. Winter temperatures between 0 and 12.8 degrees Celsius and 65 to 80 in the summer are ideal. Cherimoya is grown commercially in the United States in three counties in California: San Diego, Ventura and Santa Barbara. The seeds readily germinate, and your cherimoya tree will produce fruit three to four years after planting the seed.
Fill a nursery pot with equal parts of compost and potting soil. Water the soil until it is drenched and allow it to drain.
Push the cherimoya seeds 1 inch into the soil. Set the thermostat on the heat mat to 23.9 degrees Celsius and place it in a bright area, but out of direct sunlight. Keep the soil slightly moist at all times. The cherimoya seed should germinate within three weeks.
Transplant the cherimoya seedlings into 18-inch-deep pots when they are 3 inches tall. The cherimoya develops a long tap root and requires the deep pot to do so.
Transplant the cherimoya into a sunny spot in the garden the first fall after germination. Dig a hole the same depth and twice the diameter of the pot in which it is growing. Carefully remove the cherimoya from the pot, disturbing the tap root as little as possible. Place the roots in the hole and fill the hole with soil. Water the cherimoya slowly, until the water puddles at the base.
Water the cherimoya to keep the soil slightly moist when it is producing new growth. Decrease the amount of water to half when the tree is dormant.
Fertilise the cherimoya every three months with an 8-8-8 fertiliser, at the rate listed on the label. Sprinkle the fertiliser at the tree's dripline, rake it back to within 6 inches of the trunk and water to a depth of 3 inches.