Star Fruit Tree: Growing Unique Tropical Fruit
What is star fruit? You’ve come to the right place. The star fruit is a rich source of vitamin C, B9, B6, B2, and dietary fiber. It also contains various minerals, such as potassium, zinc, phosphorus, and iron. It’s a low-calorie fruit, with only 31 calories per 100 grams. And the star fruit tree is beautiful, too!
A mature tree can produce as much as 200 to 400 pounds of fruits every year. The star fruit is pulpy with a grape-like texture. The flavor is described as similar to feijoa, but with hints of banana and pear and the acidity of pineapple.
It’s also a widely popular ornamental plant. With beautiful foliage and lovely clusters of lilac-colored flowers, this tree can enhance the aesthetic appeal of your garden. The flowers also attract bees, so it can entice more pollinators to your yard.
Good Products When Caring For A Star Fruit Tree:
- Bonide All-Seasons Horticultural & Dormant Spray Oil
- Safer Brand Insect Killing Soap
- PyGanic Organic Pyrethrin Concentrate
- Serenade Garden Disease Control
- Monterey Liqui-Cop Liquid Copper Fungicide
Quick Care Guide
|Common Name(s)||Starfruit, carambola, five-finger, bilimbi|
|Scientific Name||Averrhoa carambola|
|Days to Harvest||60 to 75 days after the fruit sets|
|Water:||Regular watering, 2-3x per week if no rain|
|Soil||Well-draining, many soil types|
|Fertilizer||Depends on age of tree|
|Pests||Scale insects, weevils, stink bugs, squash bugs, thrips|
|Diseases||Fungal leaf spot, algal rust, anthracnose fruit rot, pythium root rot|
All About Star Fruit
The star fruit plant goes by the botanical name Averrhoa carambola. However, the tree and the fruit have many common names in different regions. For example, in Spain and the surrounding areas, the tree is known by the name carambola. In Indonesia, it is called bilimbi, although that name also refers to Averrhoa bilimbi, and thus isn’t used to refer to star fruit often.
The Averrhoa carambola tree is generally multi-branched, with dark-green bushy foliage. It can grow up to 20 to 30 feet in height and 20 to 25 feet wide, but is often maintained in a smaller size for ease of harvest.
It produces small, bell-shaped flowers with five petals. Their color is lilac, but they have purple streaks along the petals. When grown in tropical conditions such as the southern parts of Florida, the plant typically blooms in April and May but may produce a second bloom in September to October. A few scattered flowers can appear year-round.
The star fruit season is long, with harvestable fruit appearing from June sometimes all the way to the following February. Roughly oval in shape, the fruit has deep indentations along its sides. When cut in cross-sections, the indentations make it form a star, hence the name of starfruit. It is usually light to dark yellow in color with slightly darker skin.
There are many types of carambolas, but they fall into one of two categories: sweet, or tart. The tart varieties are generally used as a garnish or in savory applications such as curries or stews. The sweet ones are used for jams and jellies, juicing, cocktails or desserts.
Like other exotic fruits, it may not be for everyone. The starfruit contains enough oxalic acid that it may be potentially risky for people with kidney disease to consume it.
Starfruit hails from tropical Southeast Asia, where it has been cultivated for centuries. It was introduced to the subcontinent and Sri Lanka by Austronesian-speaking traders. Today, it is cultivated and enjoyed almost all over the world, with Australia, Malaysia, Philippines, Taiwan, and the USA being the top producers. India is the biggest producer in Southeast Asia.
Planting Star Fruit Trees
Planting a starfruit tree in your garden can be a lot of fun. Plus, the delicious fruit is well worth it if you’re in the right area to grow it! Here’s some tips on planting these the right way.
When To Plant
As a tropical, the star fruit tree should be planted in locations where frost isn’t likely. Having said that, it’s still wise to plant this tree in the early spring to ensure it has time to settle in prior to the hot months.
If starting a carambola seed, they require warm soil to germinate. Make sure you’re using a seedling heating mat at a temperature of at least 70 degrees to ensure good germination. You’ll likely still need to have young trees container grown for a while before you transplant into the soil, possibly as much as 2-3 years.
Where To Plant
Full sun is necessary for good star fruit growth. Make sure your starfruit tree receives at least 8 hours of sunlight every day, and that it’s sheltered from winds.These plants are not tolerant of high winds, cold climates, or in alkaline soils.
Your tree should be 20-30 feet from any other trees or from structures. This reduces the likelihood of the tree getting too much shade. Similarly, trees that are grown in containers need to be well away from other trees and structures to enable good growth.
How To Plant
Once your plant is roughly 2-4 feet in height and has sized up to at least a 3-gallon container, it’s time to plant it in the soil. Be sure it isn’t rootbound and that it’s in good health. Try planting young trees in Air Pots, as these are expertly-designed to promote the healthiest possible roots.
Prepare your soil in advance by loosening it up in the area where the roots will grow. Do not apply fertilizer, compost, or other additives to the soil. Instead, make sure that if there’s large rocks that they’ve been removed, and that the soil is well-draining and slightly acidic. Plant at the same depth the tree was planted in its pot, but no deeper.
The carambola is fairly low-maintenance once established, provided you’re giving it the right care. Let’s go over the conditions that your tree wants to produce incredible star fruit!
Sun and Temperature
Carambola plants prefer full sun conditions. The plant prefers a hot and humid environment and is prone to frost damage. Temperatures under 35 degrees get steadily more dangerous, and temperatures below 25 degrees can cause tree death.
When grown outdoors, it performs best in the USDA zones 9 to 11. The temperature must be 60° F or higher for good tree health, and preferably 70-95 for fruit production.
Watering and Humidity
Not a drought-tolerant species, your carambola will need regular watering. Keep the soil moist, but not over-saturated, at all times. Aim for 1-2 deep waterings per week if there hasn’t been rain. Reduce watering in the winter months when it’s unnecessary. A soaker hose around the tree can be used to do a slow, deep watering, but base your placement on a ring that’s at about the midpoint of the tree’s canopy all the way around.
Your tree can tolerate flooded conditions for between 2-10 days, depending on its current health, but will begin to suffer from lack of oxygen around its roots. It’s better to avoid flooding for this species, but if it can’t be avoided, it won’t immediately suffer damage.
Humid environments are great for this species. However, watch for any symptoms of plant diseases that are common in humid locations.
Once your tree is 1-2 years old, consistent irrigation is important from flowering through fruiting. Make sure it has the water it needs to produce lots of fruit.00
Carambolas do well in a wide variety of soil textures. As long as the soil drains off excess moisture, it should be fine to plant your tree in.
Slightly acid-loving, to grow star fruit you’ll need an acidic to neutral pH range. In more alkaline pH levels, they are susceptible to nutrient deficiencies. Aim for a range between 4.5 and 7 for best growth.
Carambola trees are moderately-high feeders. Mature trees should be fertilized 4-6 times per year, and young trees every 30-60 days throughout the growing season. Aim for a 6-2-6 or 6-4-6 fertilizer range when possible, preferably one that includes micronutrients such as manganese, iron, zinc, and magnesium.
If your tree is in alkaline soil, it may suffer from nutrient deficiencies. These should receive foliar sprays 4-6 times a year that contain manganese, iron, and zinc.
In the first 1-2 years after planting, tip trimming branches in excess of 3 feet in length will encourage lateral growth. This should be done during the winter while the tree is dormant. Mature trees can be trimmed to maintain them at 6-12 feet in height for ease of harvest.
Each year, it’s also good to examine the tree closely and make sure there are not any inward-growing branches. Selective pruning at the crotch of the branch to remove a couple inward-growing branches will improve airflow and light to the rest of the canopy.
Propagation of these trees is typically one of two methods: from seed, or from grafting. Other methods are rarely effective.
Grafting a carambola branch onto another rootstock is a common technique used to generate nursery stock. However, it’s not an easy process, and is likely best left to the professionals.
Harvesting and Storing
The only thing better than growing the Carambola plant is enjoying the harvest! Here’s how to harvest and store the delicious, tangy fruits.
Star fruit does not ripen once it’s harvested. When the grooves in the sides of the fruit are completely yellow, and only the very upper tips of the raised sections are still green, it’s time to start harvesting. You can wait for the upper tips to turn yellow as well, but it won’t have as long of a storage life if you do.
Your harvested star fruits can be stored in a sealed plastic bag in the refrigerator for up to 21 days. Most starfruit is consumed fresh, rather than stored for longer periods of time.
For longer-term storage, puree the star fruit and freeze it in an ice cube tray. You can also dry starfruit using a food dehydrator. The puree can also be used to make jams or jellies. Remove the seeds while processing it for storage.
Let’s discuss problems you might face with your home-grown star fruit plants as you care for them. There aren’t a lot of them, but they do exist!
Soil above a pH level of 7 can cause your home-grown carambola tree to suffer from nutrient deficiencies. An iron deficiency can cause yellowed leaves with green veins or smaller-sized leaves. Manganese deficiencies cause reduced leaf size and yellowing of leaves. Magnesium deficiencies produce mottled yellow and green leaves. Treat with the appropriate micronutrient if these appear.
In addition, while mature trees can handle cold temperatures for short periods of time, it comes with varying stages of potential damage. At temperatures below 60 degrees Fahrenheit, carambola fruit production stops. At temperatures of 30-32 degrees, young leaves can die off. Young trees, mature leaves and young branches can be killed at temperatures between 25-29 degrees. Temperatures 24 degrees and below can kill mature trees.
Three different types of scale insects are common pests for carambola. Plumose scales (Morganella longispina) and philaphedra scales (Philephedra tuberculosa) attack leaves and twigs. Brown scales (Coccus hesperidum) attack the fruit directly. Regular spraying of horticultural oil will reduce the appearance of these.
Two types of weevils stop by, too. The diaprepes weevil (Diaprepes abbreviatus) causes damage to roots and can cause root and shoot dieback. A fruit weevil called Myctides imberbis can also appear intermittently, consuming the delicious starfruit. These are both treatable with pyrethrin.
Stink bugs and squash bugs both can create small holes in the fruit that can then allow in fungal or bacterial pathogens, causing the fruit to rot. Insecticidal soap is effective against stink bugs. For squash bugs, pyrethrin is a better bet, and it’s effective against stink bugs as well.
At least one kind of thrips, red-banded thrips, attack the flowers and fruit as well. Treat with insecticidal soap, neem oil, or horticultural oil to deal with these pests.
An assortment of fungal leaf spot diseases are common on star fruit. Cercospora averrhoa, Corynespora cassiicola, Gloesporium sp., Phomopsis sp., and Phyllosticta sp. are all fungal pathogens that cause these. While typically not very dangerous to your tree, they do provide the warning that your tree is suffering some sort of stress. This could be nutritional deficiencies or stress due to the climate. No control is necessary, only determining the cause of the stress and easing it.
Algal rust is caused by Cephaleuros virescens. This form of rust causes rough grey or red circular patches on the bark and can result in twig dieback. If you believe your tree is experiencing algal rust, contact your local agricultural extension to confirm and to provide information on treatment options.
Anthracnose fruit rot is not uncommon, but you’ll usually see anthracnose leaf spotting first. Treatment of the leaves should prevent the spread to the fruit and to prevent a risk to your tree’s fruit production. To treat, use either a biofungicide that contains Bacillus subtilis, or use a copper fungicide spray. Once fruit is infected, dispose of the damaged fruit.
Finally, root rot caused by Pythium fungi can occur in overly-wet soil conditions. Make sure the soil around your tree readily drains off excess moisture. Some soil mycorrhizae are showing signs of helping protect plants against fungal root rot, but there is no cure once the star fruit tree is already infected, so prevention is essential.
Frequently Asked Questions
Q: How long does it take for a star fruit tree to bear fruit?
A: In the first year, star fruit trees typically don’t produce much if any fruit. After you care for it through its first year, you can expect fruit in either year 2 or 3. Home-grown star fruit trees that are protected from high wind can often be harvested within 10-14 months of planting provided that they’re 2 years or older.
Q: Are star fruit seeds poisonous?
A: Yes and no. For people who have kidney disease, star fruit is generally not recommended at all, as it contains high amounts of oxalic acid. If you are healthy, the seeds or fruit should not harm you.