Kumquat

Tree facts

Scientific name

Citrus japonica

Origin

Southern China

Tree size

6–15 ft; easy to keep small or in a pot

Growth rate

Slow

Sun

Full sun

Soil

Any soil that drains well, including sand. Never waterlogged; plant high where water stands.

Soil pH

6.0–7.5

Pollination

Self-fertile; one tree is enough

Cold hardiness

Among the hardiest citrus; dormant trees take about 18°F

USDA zones

9–11 (8b with protection)

Years to first fruit

2–3 for a grafted tree

Season

Nov–Mar

Water

About every 7 days once established, without rain; more in heat, in pots and while young

Feeding

About every 60 days, Feb–Oct

Pruning

Mar–Apr

Taste

Sweet, fragrant peel around tart, juicy flesh

Nutrition

High in fiber and vitamin C, since the peel is eaten

Is kumquat safe to eat? Edible and toxic parts

What you can eat

• Whole ripe fruit, peel included (spit out the seeds)
• Cooked into marmalade, candied, or preserved in syrup or salt

Toxic parts and cautions

• Good to know: Kumquats are eaten whole, so they're a choking risk for small children. Halve and seed them for little ones.
• Good to know: Citrus juice or peel oil left on the skin in strong sun can cause a burn-like rash that darkens the skin for weeks (phytophotodermatitis). Wash your hands after peeling or squeezing fruit outdoors.

Pets: Don't share whole kumquats with pets. The peel, leaves and seeds contain essential oils (limonene, linalool) and psoralens that can cause vomiting, drooling and skin irritation in dogs and cats. A bite of the flesh is usually harmless.

How to eat and enjoy kumquat

• Eaten whole, straight from the tree
• Candied kumquats and marmalade
• Salt-preserved kumquats, stirred into hot water for sore throats (China and Vietnam)
• Sliced into salads and cocktails
• Potted trees as a Lunar New Year symbol of good fortune

Kumquat varieties (5)

• Centennial Variegated · also Centennial

  A Nagami-type kumquat with cream-and-green leaves and green-striped young fruit that turns orange as it ripens.

  Taste: Tart, like Nagami · Size: Small, oval

  Grown as much for looks as for fruit.

• Fukushu · also Changshou

  A larger kumquat with thin, sweet peel on an attractive compact tree with broad leaves.

  Origin: China, via Japan · Taste: Sweet peel, mildly tart flesh · Size: Medium for a kumquat

  Often grown as an ornamental.

• Marumi · also Round kumquat

  A small, round kumquat with sweet peel and tart flesh on a slightly thorny tree.

  Origin: China, via Japan · Taste: Sweet peel, tart flesh · Season: Nov–Mar · Size: Small, round

  One of the more cold-hardy kumquats.

• Meiwa · also Sweet kumquat

  A round kumquat with thick, sweet peel, the sweetest for eating fresh.

  Origin: China · Taste: Sweet throughout · Season: Nov–Mar · Size: Small, round

  Many consider it the best kumquat for eating out of hand.

• Nagami · also Oval kumquat

  The common oval kumquat, with tart flesh; the best type for candying and marmalade.

  Origin: China · Taste: Sweet peel, tart flesh · Season: Nov–Mar · Size: Small, oval

Pests and diseases to watch for

• Citrus greening (HLB)

  Blotchy, uneven yellowing that isn't the same on both halves of a leaf; small, lopsided, bitter fruit that stays green at the bottom; twig dieback.

  What to do: There's no cure. Keep the tree well fed with a complete citrus fertilizer and micronutrients to slow decline.

  A regulated disease in Florida, Texas, California and elsewhere. If you suspect it, contact your county extension office or the state agriculture department.

• Citrus leafminer

  Silvery, winding tunnels in young leaves, which curl and twist.

  What to do: Mostly cosmetic on mature trees; leave them be.

• Scale insects

  Small bumps, waxy or shell-like, on stems and leaf veins; sticky honeydew and black sooty mold below.

  What to do: Scrub small colonies off with a soft brush.

• Mealybugs

  White cottony clusters in leaf joints, under leaves and on fruit stems; honeydew and sooty mold.

  What to do: Blast off with a strong spray of water.

• Aphids

  Clusters of tiny soft insects on new shoots; leaves curl and get sticky.

  What to do: Spray off with water.

• Sooty mold

  Black, papery film on leaves and fruit that wipes off; it grows on honeydew.

  What to do: Control the insects making honeydew; the mold then weathers away.