The starfruit tree, or carambola, is a slow-growing evergreen tree with a pleasantly-shaped, rounded top. A mid-size tree, the starfruit tree will eventually top out at about 25 to 30 feet. The tree will produce sweet-smelling, lavender or pink flowers several times a year, followed by tart, juicy, star-shaped fruit. Although the starfruit tree isn't difficult to grow, healthy development requires requires temperatures of at least 55 degrees F.
Choose a healthy star fruit tree at a greenhouse or nursery. Star fruit trees are usually grown in three-gallon containers, with the tree extending between 2 and 4 feet above the level of the soil. Avoid large starfruit trees grown in small containers, which may be root-bound.
Choose an appropriate planting site for the starfruit tree. The tree is susceptible to both hot and cold winds, so plant it where it will be sheltered from strong winds. The site should be in full sunlight, and the soil should drain rainwater freely.
Dig a hole for the starfruit tree. The hole should be only as deep as the root ball, but two to three times as wide.
Place the starfruit tree in the hole, and be sure the top of the root ball is about an inch above the soil. Ask a friend to hold the trunk straight while you fill the hole halfway with soil. Let a garden hose run slowly into the hole until it's full, then allow the water to drain. Once the water has drained, continue filling the hole with soil, tamping the soil down lightly with your foot.
Fertilize the starfruit tree four or five times each year, using a fertilizer formulated for fruit trees. Spread a 4 to 6-inch layer of organic mulch around the tree, but keep the mulch 8 to 12 inches away from the trunk. Mulch will collect moisture and heat, which can invite mildew and insects if it piles up against the trunk.
Water the starfruit tree regularly during its first year, but don't water excessively, which can cause root rot. A weekly, deep watering is better than frequent, shallow waterings. Once the tree is established, water it regularly while it's flowering, to facilitate development of the fruit.
Leave at least 4 to 5 feet between the starfruit tree and lawn so the tree won't be damaged by a lawn mower, and be careful when using weed trimmers near the tree. Damage to the starfruit tree's trunk can slow growth, and if damaged is allowed to continue, it will eventually kill the tree.