Starfruit trees (Averrhoa carambola) are very attractive, with curving branches and large masses of lilac-purple blossoms that attract pollinators. They are grown for their ornamental value as well as their fruits, which, at maturity, are about 5 to 7 inches long and turn from a bright olive green to a greenish yellow as they ripen, culminating in a warm bright yellow when fully ripe. The skin is shiny and can be left on the fruit when eaten. The fruits seem to combine the flavors of a number of other fruits including kiwi, pineapple, berries, and grapes. The fruit is juicy and somewhat crunchy, with a consistency like firm green grapes. Throughout Southeast Asia it is used in various cuisine, and the juice is used in beverages.
Growing up to 30 feet tall, starfruit trees are covered with glossy leaves in summer followed by the pendulous fruits. There are two main types of starfruit grown commercially: the smaller sour fruits (including 'Golden Star,' 'Star King, and 'Newcomb," all grown in Florida), and the larger sweet ones ('Arkin,' 'Maha' and 'Dmak' grown in Florida, Malaysia and Indonesia respectively). As a soluble calcium oxalate plant, starfruit is toxic to dogs and cats.
|Botanical Name||Averrhoa carambola|
|Plant Type||Fruit tree|
|Mature Size||Up to 30 feet (dwarf trees reach 3 feet)|
|Sun Exposure||Full sun|
|Soil Type||Loam, moist, good drainage|
|Soil pH||Slightly acidic|
|Flower Color||Pale purple|
|Hardiness Zones||9 to 11 (USDA)|
|Native Areas||Southeast Asia|
|Toxicity||Toxic to dogs, toxic to cats|
Starfruit Tree Care
Starfruit has only been cultivated in the United States since the 1970s, thanks to an amateur horticulturalist in Florida who decided to grow a tree in his backyard. Due to concerns over pests, the fruit itself cannot be imported into the United States, so growers in Florida and Hawaii provide domestic supplies of starfruit to consumers. These two states have the best growing conditions, with their semi-tropical climate, abundant sun, and frequent rain.
If your growing zone isn't warm enough to grow starfruit trees, you can try growing dwarf trees in containers, to be overwintered indoors. The best varieties for container growing are known as 'Hawaiian Dwarf' and 'Maher Dwarf.' These trees grow to a maximum height of 3 feet and are perfect for an indoor setting.
The starfruit tree does best in a loamy soil with good drainage. If creating your own soil mix, using topsoil, compost, and a bit of sand (10%) should yield a good result.
This tree needs plenty of bright sunlight to flourish—at least 7 hours of direct sun per day. If growing in a container and overwintered indoors, make sure it has a sunny window and turn the tree occasionally to give it full exposure on all sides.
Water your starfruit regularly. Heavy consistent rain or overwatering may inhibit fruit production.
Temperature and Humidity
The starfruit tree is tropical and can't survive in a region where temperatures dip below freezing. However, it can be grown in containers in colder zones if it is moved indoors for winter into a greenhouse or sunny room. It needs temperatures of at least 60 degrees on a consistent basis in spring to set fruit, and does best with temperatures over 70 throughout the summer, when it flourishes in the sun. Being tropical it also responds well to humidity, and misting it with cool water regularly (at least once or twice a week) keeps the leaves looking lush.
Prune the tree lightly in early spring to keep it looking neat and encourage balanced placement of fruiting branches. If the branches bend under the weight of the fruit, this is a sign that it needs pruning.
The seeds of starfruit don't usually remain viable long enough to grow the trees from seed, so it's best to reach out to a nursery to obtain a tree. It's also possible to graft starfruit branches onto other fruit trees with a similar growth cycle and climate needs.
Common Pests & Diseases
Starfruit trees are somewhat susceptible to various pests, including carambola fruit flies, ants, and some birds who enjoy snacking on the fruit. They may also be attractive to weevils, stink bugs, squash bugs, and thrips. They're also prone, like other fruit trees, to some of the following diseases: fungal leaf spot, algal rust, anthracnose fruit rot, and pythium root rot.
Toxic Plants. ASPCA Animal Poison Control Center, Urbana, IL. Isvma.org. https://www.isvma.org/wp-content/uploads/2016/10/ToxicPlants.pdf