Calamondin

About Calamondin

Calamondin, called calamansi in the Philippines, is a small, upright, nearly thornless citrus thought to be a natural cross of a sour mandarin and a kumquat. It bears loads of tiny, very sour orange fruit and fragrant white flowers much of the year. It is the citrus most often grown as a houseplant.

NC State lists zones 8b-11b; UF says it is hardy to about 22 F once established, and young trees need protection.

When to plant

Timing is counted from your average last spring frost (and first fall frost). Sow & Tell works out the actual dates for your ZIP code.

• Set out plants: up to 2 weeks after the last frost

A potted tree goes outside after the last spring frost and is eased into full sun over about two weeks (Maryland Extension; Wisconsin says wait until temperatures stay above 50 F). Budded citrus usually starts bearing in its second or third year (Texas A&M).

Soil

Well-drained soil rich in organic matter, acid to neutral (NC State); in pots a fast-draining mix with some peat (Minnesota Extension).

Pot it in a fast-draining, slightly acid potting mix (bark-based, or palm-and-cactus mix) in a container with drainage holes, never garden soil; in the ground, test the soil and keep the pH around 6.0-7.0 (Mississippi State; UC Master Gardeners; UGA).

Feeding

• First feeding after planting, once new growth starts (about 4 to 6 weeks): citrus fertilizer with micronutrients (about a 2-1-1 or 3-1-1 N-P-K ratio with iron, manganese and zinc, or a slow-release 12-6-6 or 12-4-6). Follow the label for a pot; in the ground, UGA starts a young tree with about 1/3 lb of 8-8-8 with micronutrients spread in a 30-inch circle and watered in.
• Early spring each year, as new growth begins: citrus fertilizer with micronutrients (N-P-K about 2-1-1 or 3-1-1). Slow-release granules need 2 to 3 feedings a season; a water-soluble citrus food can instead go on about once a month from late winter to fall (Clemson; Maryland; UC Master Gardeners; Texas A&M).
• Early summer: citrus fertilizer with micronutrients. Repeat the spring feeding at the label rate and water it in (Maryland Extension).
• Late summer (the last feeding of the year): citrus fertilizer with micronutrients. Give the final feeding, then stop by early fall so new growth can harden before winter; in the ground, UGA says no fertilizer from August 1 to February 15.
• Any time young leaves turn yellow with green veins: chelated iron fertilizer or a sulfur soil acidifier. Apply as the label directs; this pattern usually means iron is short or the mix is not acid enough (Maryland Extension).

Don't feed through the winter indoors (Wisconsin and Minnesota feed only about April to September), and don't overwater or let the root ball dry out: too much water drops leaves and too little drops flowers (Maryland; Mississippi State).

Harvest

Fruit starts green and turns orange as it ripens, which can take up to a year; trees flower and fruit on and off all year (NC State; UC Riverside).

Calamondin blooms in spring and then repeats 4 to 5 times through the season, so a tree often has flowers and fruit at once. Fruit can take up to a year to ripen, so pick as fruits turn orange.

Varieties (2)

Only two garden forms are documented: the regular calamondin and the variegated form. UC Riverside also keeps a few research selections that are not sold.

Pests to watch for

Scale insects, Mealybugs, Whiteflies, Twospotted spider mite, Aphids, Citrus leafminer, Asian citrus psyllid

Diseases and problems

Root rot, Sooty mold, Citrus greening (HLB)

In the kitchen

Too sour to eat out of hand; the juice is used like lemon or lime in drinks and cooking, and it is an important juice fruit in the Philippines (UF/IFAS; NC State; UC Riverside).

Keeping it: Fruit holds well on the tree, so pick as needed. Like other citrus, picked fruit keeps a few days on the counter or longer in the refrigerator.

Safety: The fruit is eaten as a food. The sources we checked list no toxic parts for people, and we found no research-based guidance on pregnancy, drug interactions or allergies.

Pets: Toxic to dogs, cats and horses (ASPCA, listed as calamondin orange): essential oils and psoralens can cause vomiting, diarrhea, depression and sun-sensitive skin irritation.