Edible PlantsFruits

How To Grow a Star Fruit Tree?

star fruit tree

The Star Fruit tree, scientifically named Averrhoa carambola, is native to tropical Southeast Asia. As with any famous plant, this one has multiple names, such as the Star Fruit, Five-Corner, and Carambola.

This shrub can grow to a height of 16 or 39 feet (4.9-11.9 m). Mostly this tree is cultivated for its edible fruit called the star fruit or Carambola. The fruit has five to six ridges running alongside it, which make it look like a star when cut open cross-section.

The whole fruit is edible and can be eaten raw, even the fruit’s slightly waxy skin can be eaten. Best eaten right after they ripen and all colors of green have turned yellow on the fruit. The fruit has a sweet taste whilst only having no more than 4% sugar in it, texture is close to a grape.

The tree also produces flowers all year long if grown in a tropical environment. The flowers are usually bell-shaped and quite small, with colors ranging from rose to red-purple. Each flower has five petals whose edges are colored white.

The tree itself is a fast-growing shrub with a short wooden trunk and small leaves. The leaves are mostly drooping whilst the trunk of the tree is often colored white turning red. Each leaf is usually 5.9 to 7.9 inches (15-20 cm) long.

The top side of the leaves is smooth and the underside is coated with tiny hairs and colored slightly white. The Star Fruit tree will not gift you with fruit on the very first year after being planted, it can take up to five years before you can start enjoying the fruit of this tropical tree. 

Consuming Star Fruit

Consuming large amounts of star fruit can cause serious health defects, especially for a person suffering from some type of kidney disease. People with healthy kidneys can pass and process the neurotoxin which comes from the fruit but people with kidney problems can not. The person with kidney problems should consult their doctor before consuming the star fruit. 

Varieties of Star Fruit

Star Fruit Arkin: this variety is the sweet version of the original. Their fruit is bigger and is usually pale green.

Star Fruit (sour): this variety is the sour version of the original. Their fruit is smaller and usually colored light green.

How To Grow?

The Averrhoa carambola is winter hardy in USDA Hardiness zones ten through twelve. The best annual daytime temperatures for this tree would be between 75.2 and 86°F (24-30°C). A young plant can be killed by temperatures as low as 30°F (-1°C), mature plants will be killed by temperatures as low as 28°F (-2°C).

The tree might stop growing altogether when the temperature drops to 65°F (18°C).  Place or plant the tree far away from other big trees, buildings, and power lines. Place the plant somewhere where the shrub will be protected from wind. 

pile of star fruits
Pile of star fruits

Light

The Star Fruit tree will need full sun to thrive. This shrub prefers to be in the sun all day long if possible. The sun will help produce the tree with healthier and tastier fruit. Sunburn symptoms may be very hard to notice, so keep an eye on your plant.

If you notice your plants drying up and their leaves changing from green to a burnt yellow then remove any burned leaves and move it to a less sunny spot for a little while.  This plant will need at least seven hours of full sun in a day to truly thrive. 

Watering

Your Averrhoa carambola is not a drought-tolerant plant, so a good watering routine is crucial. The soil should be kept moist but not too soggy, otherwise, you will have to deal with root rot.

If your tree grows outside, and there has not been any rain for a long time, aim to water your plant thoroughly twice a week. Reduce watering in the winter. If temperatures rise above 95°F (35°C) you will need to keep the plant moist and water it more often.

Star Fruit tree does not tolerate flooding so make sure not to over-water. Again, watering the plant regularly can help produce healthier fruit. If the top few inches of the plants surrounding soil is dry, which you can check by tipping your finger in it, means it is time to water your plant.  Usually watering your tree every one or two weeks should suffice. 

blooming star fruit tree
Blooming star fruit tree Source: Wendy Cutler

Soil and Fertilizer

This shrub is capable of growing and surviving in many types of soil, such as clay loam, rocky soils, and sand. However, the most recommended soil for this plant would be loamy soil that is well-draining. The pH level in the soil should be between 5.5 and 6.5, meaning acidic. 

For fertilizer, it is recommended to use slow-release or organic granular fertilizers. If your plant is grown in a container it should get fed balanced fertilizer from spring to fall. Fertilizer should be applied every few months. 

Pruning

Young trees should be pruned during their first two years after being planted regularly. They should be pruned to increase branching by tipping above two to three feet (0.6-0.9 m). The best time for pruning would be in the spring. When pruning make sure to use clean and sharp tools.

Pruning will encourage the balanced placement of fruiting branches. Pruning is mostly done to keep the tree looking nice and neat, it can also be done when removing infected, diseased, or broken branches. 

Averrhoa carambola
Averrhoa carambola Source: Forest and Kim Starr

Propagation

When propagating a Star Fruit tree, grafting is the most popular option: grafting is a way of cloning, meaning you attach a branch from another tree to the rootstock of the Star Fruit tree. The two pieces will grow to be one tree and start producing fruit. 

Repotting

You will only need to repot the Star Fruit tree if you are changing its nursery pot for a new one. This will need to be done when the new plant has matured about two years after potting it. Use the recommended soil and make sure to water it accordingly. 

Diseases

Whilst growing your Averrhoa carambola you may come across diseases such as brown spots, algal disease, Cercospora leaf spot, flyspeck, and root rot. To cure your plant of these diseases you can use copper-based fungicides or foliar fungicides.

To avoid these diseases altogether make sure not to harm the fruit, make sure when planting to not place the tree in a known spot for diseases, and care for the tree accordingly. Keep an eye on your plant to spot the disease early on for easy treatment.

Pests

You may come across pests that attack the tree’s leaves, fruit, and branches such as stink bugs, squash bugs, scales, plumose, brown scales, red-banded thrips, and weevils. To clear your tree of these pests you can use a mixture of baking soda and soap mixed with water.

Use it by spraying the plant with it regularly until no more pests reside. Some pests can also be picked off by hand. You can also use neem oil or insecticidal soap. Keep an eye on your plant to spot intruders early on for easy removal. 

Conclusion

This fast-growing, fruit-bearing shrub can be a very rewarding plant to grow for anyone. If you succeed in keeping the plant healthy not only are you graced with beautiful flowers you will also receive fruit. The fruit can not only be eaten raw but can also be juiced, cooked, grilled, or made into a salad.

The placement of the plant will make it stand out as it will need a lot of space. The tropical look of the tree, its leaves, fruit, and flowers will make any space look more alive and special. 

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