Caren White is a Master Gardener and instructor at Home Gardeners School. She has been associated with Rutgers Gardens for over a decade.
A gardening friend asked me if I would like an orange tree. One of her coworkers had grown several seedlings from seed and was sharing them to anyone who was interested. She showed me a photo of the parent tree and with a little research, I determined that what I was being offered was a calamondin orange, which is suitable for indoor container growing.
What is a Calamondin Orange Tree?
Calamondin orange trees (Citrus × microcarpa) are a hybrid resulting from a cross between a kumquat and a mandarin orange. The fruit has a sour taste that is more like lemons or limes than oranges. The trees are native to Indonesia and southern China. The fruit is integral to Philippine cuisine. Calamondin were introduced to the US in 1900.
The trees are hardy in zones 8b – 11. Gardeners in colder zones bring them indoors during the winter.
Calamondins are small trees, growing to a height of 10 - 20 feet. They can be kept to 6 – 10 feet if grown in containers and pruned. The trees are columnar in shape meaning that they are taller than they are wide.
The leaves are oval. They are glossy and dark green on the upper sides and yellowish green on the undersides. They grow to 3 inches in length.
The flowers are very fragrant. Not surprisingly, they smell of oranges. The flowers appear at the ends of the branches in bunches of 2 or 3. They are white and about 1 inch wide.
The flowers are self-fertile which means that they don’t need another calamondin tree to pollinate them. When grown outdoors, the flowers are pollinated by the local insects. When grown indoors, if you want fruit, you will need to pollinate the flowers by hand using a small paintbrush.
Calamondins will bear fruit year-round. The largest amount of fruit is produced from November to June.
The fruit is round and small like a lime. It is usually 1 – 2 inches in diameter although some grow to 2 inches in diameter. Inside of the fruit, the pulp and the juice are orange like a tangerine. The rind is also orange and very thin. The fruit can take as long as a year to ripen. The longer you leave the fruit on the tree, the sweeter it will be. Each fruit produces 8 – 12 seeds.
How to Grow Calamondin Orange Trees Outdoors
For gardeners lucky enough to live in zones 8b – 11, they can grow their calamondin oranges outdoors in their gardens. The trees tolerate a wide range of soils. Grow your trees in full sun to part shade. Water them deeply and then allow the soil to dry before watering them again. Too much water will kill them.
Fertilize with either a fertilizer specifically formulated for citrus or for acid-loving plants such as azaleas and camellias. Fertilize as the trees are coming out of dormancy in late February and then again in both May and July.
How to Grow Calamondin Orange Trees Indoors
Most gardeners grow their calamondin orange trees indoors in containers, putting them outdoors only during the summer. When grown indoors, the trees need to be somewhere where they will get a lot of light. A south facing window is best.
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They grow best in temperatures ranging from 70°F - 90°F, so keep them indoors until the nighttime temperatures outdoors reach 70°F. Bring them back indoors in the fall when the nighttime temperatures fall below 70°F. During the winter, keep them away from drafts from outside doors.
Calamondin oranges like to grow in slightly acidic soil. You can make your own by combining 1/3 potting soil, 1/3 peat moss and 1/3 compost.
Water regularly just like you do with your houseplants, allowing the top of the soil to dry out between waterings. Calamondin oranges need humidity and our homes are too dry for them. You will need to provide your tree with humidity either by misting it or using a humidity tray.
During the growing season, fertilize monthly with a water soluble fertilizer at full strength. During the winter, cut the fertilizer back to half-strength.
How to Harvest Calamondin Oranges
When to harvest your calamondin oranges depends on what you want to use them for. They take up to a year to fully ripen to an orange color. That is when the fruit is at its sweetest. If you prefer a more sour flavor, for instance if you want to substitute it for lemons or limes, it’s best to harvest the fruit when it is half-ripe, with only a little orange color.
The rind on the fruit is very thin and very fragile. If you try to harvest by pulling the fruit from the branch, the rind will tear. Use scissors or small pruners to carefully cut the stem from the branch.
How to Store Calamondin Oranges
Calamondin oranges have a very short shelf life. You should use them within a week if you are not refrigerating them. Like most citrus, the fruit starts to decay the minute you cut them from the tree.
Store your oranges in the crisper drawer of your refrigerator for best results. Stored in a refrigerator, the fruits will last 2 – 3 weeks.
How to Prune Calamondin Orange Trees
Plan on pruning your calamondin orange tree in February or March, whether it is growing indoors or outdoors. That is when the trees are coming out of their winter dormancy period and beginning to grow again.
Always remove any dead or diseased branches. The trees don’t require a lot of pruning. Most gardeners who grow them outdoors, prune them to shorten their height to make it easier to harvest the fruit. Gardeners in colder climates who grow them in containers, prune both the branches and the roots to keep their trees small and easy to transport in and out of the house depending on the season.
How to Propagate Calamondin Orange Trees From Cuttings
Calamondin oranges trees can be propagated using either softwood cuttings taken in the spring when the plant is actively growing or hardwood cuttings taken in the fall when the tree is entering dormancy.
Make an 8 inch cutting from a branch that doesn’t have flowers or fruit on it. If you use a branch with flowers or fruit, it will put its energy into growing fruit rather than roots. Remove the leaves from the bottom half of the cutting and dip the cut end in rooting hormone.
Gently press your cutting into a container filled with pre-moistened slightly acidic soil. Then place a straw next to it and cover the whole thing with a plastic bag to create a mini greenhouse. The straw keeps the plastic bag upright so that it doesn’t squash the growing seedling.
Set the bagged container on a sunny windowsill. Keep the soil moist. Roots should start to grow in 2 – 4 weeks. You will know that roots are growing because your cutting will start to grow new leaves. Plants without roots cannot grow new leaves.
Once the roots start to grow, you can remove the plastic bag. You can expect to start harvesting fruit in approximately two years.
How to Grow Calamondin Orange Trees From Seed
Calamondin orange trees are easy to grow from seed. The secret is to use fresh seed from freshly harvested fruits. Plant your seeds 1/2 inch deep in a container filled with pre-moistened slightly acidic soil. Cover the container with plastic to create a mini greenhouse. Place it on a sunny windowsill and check it periodically to make sure that the soil remains moist.
The minimum temperature for germination is 70°F. The warmer the environment, the faster the seeds will germinate. Using a heat mat will help. Germination should occur in 3 - 6 weeks. At that point, you can remove the plastic.
You can expect to start harvesting fruit in approximately two years.
© 2022 Caren White