Growing Star Fruit in Containers
By Laurelynn Martin and Byron Martin
Star Fruit is a juicy tropical fruit with a delicious tart flavor. The yellow fruit is 3-4" long with a waxy skin and 5 prominent ridges. A cross-section of the cut fruit looks like a 5-pointed star. Star Fruit is low in calories and low in sugar so it's an ideal fruit for the whole family to enjoy. When it's grown in the tropics, one Star Fruit tree can provide fruit for up to three families because of its prolific fruiting habit.
Where Star Fruit Grows
Star Fruit, or Averrhoa carambola. is a tropical fruiting tree in the oxalis family that's native to tropical Asia. Widely grown throughout the warmer areas of the world, it has little hardiness but can tolerate a light frost and temperatures into the high 20's for short periods. In general it needs temperatures above freezing to prevent plant damage.
Grown as a Potted Plant
As a northern container plant, it will survive in greenhouses or sunrooms during the winter months and it should be grown outside during the summer months. During the winter, night temperatures need to be kept well above freezing. Low temperatures will often lead to leaf drop and at times, the plant will almost completely defoliate. No worries though, the plants will recover once the warm temperatures return.
High temperatures bring out the best in Star Fruit plants. In the summer, it is an active grower, flowering and fruiting in abundance. In tropical regions, the plants will flower and fruit on and off, year-round. In the north, temperatures need to be at least 60° F for flowering to begin. Full sun is a requirement for the best flowering and fruit set.
Flowering & Fruit Set
Star Fruit will flower throughout most of the year. Fruit set is greatest during the summer when temperatures are in the 80°s or higher. Once the plant sets fruit, it often produces a heavy crop. As a potted plant, not all Star fruit are created equal. Although most varieties will fruit in containers, we have found that two are particularly adept at fruit production when grown as potted plants.
'Maher Dwarf' and 'Dwarf Hawaiian' will both fruit and flower in 8-10" pots and can be maintained in containers for extended periods. 'Maher Dwarf' has small to medium size fruit and a 3' tall plant can produce a couple of dozen medium size fruit at a time. 'Dwarf Hawaiian' produces a larger fruit with a distinctly sweet flavor but only half as many on the same size tree. Generally, young grafted plants will begin blooming right away at 1.5' in height and the young tree will even bear a few fruit.
Prolific, pink flowers emerge in clusters off older wood. This characteristic allows for periodic pruning and shaping that doesn't restrict fruiting. For growing conditions in pots, the plant prefers a full sun exposure, although it can tolerate partial sun and it will still flower. Once the plant fills out in the pot, it needs frequent watering in warm, sunny weather. Drier soil does no harm and is even beneficial in promoting healthy roots but a severe wilt can the damage plant.
Feeding Container-Grown Star Fruit
Applications of a balanced fertilizer during the spring to fall growing season are needed for optimum fruit production. Slow release or organic granular fertilizers are a good choice and can be added to containers every few months.
On occasion, Star Fruit plants can show iron chlorosis, especially during the winter months. This exhibits as the interveinal yellowing of the young growth. This can be corrected with the addition of chelated iron as a foliar spray. The symptoms often disappear in the warm weather of summer.
The root system of Star Fruit is resilient and resistant to the root diseases that affect many plants in pots.
There are few insect problems with Star Fruit plants. Mealy bugs can feed on the plants and under dry conditions spider mites can cause problems but generally the plants are insect free and the fruit is not bothered by diseases or insects.
Star Fruit plants have an upward growth habit. Generally trees planted in the ground are pruned hard every year or two to maintain a manageable fruiting height. For dwarf varieties grown in containers, you should prune back the out-reaching branches. Do your pruning in late winter before spring growth starts in earnest. As the flowers form on both the young and older wood this pruning doesn't interrupt the fruiting cycle.