Citrus japonica – Kumquat

Citrus japonica – Kumquat

Kumquat is a compact citrus grown for small orange fruit with sweet aromatic peel and sharper flesh. The ripe fruit is usually eaten whole when it comes from a plant grown for edible use.

A kumquat tree stays fairly compact in a pot, with dense branching, slender woody shoots and small fruit. With steady care, Citrus japonica can grow well for years in a container.

Sweet peel, sharp flesh and compact growth

• Growth habit: Compact evergreen shrub or small tree with dense branching.
• Leaves: Small glossy citrus leaves on slender woody shoots.
• Flowers: Fragrant white flowers on mature plants during strong seasonal growth.
• Fruit: Small orange fruit, round to oval depending on the kumquat form.
• Eating quality: Aromatic sweet rind with sharper flesh. Harvest fruit for eating from plants grown for food use.
• Wintering: Bright, cool, frost-free winter care suits container kumquats well.

Kumquat range and plant labels

Kumquat is Citrus japonica, a citrus-family plant native from southeastern China to Hainan. The old name Fortunella is still seen on some plant labels.

Its slender branches build a dense evergreen canopy and may carry small thorns. White scented flowers are followed by small orange fruit that can stay on the plant for a long period.

Kumquat care in a pot

• Light: Place kumquat in very bright light, with direct sun where possible. Strong light helps the plant keep dense growth and ripen fruit.
• Water: Soak the full rootball when the upper part of the mix has dried, then let the pot drain. Fruiting plants need steady moisture, but the roots still need air.
• Substrate: Use an airy citrus mix that drains well but still holds light moisture. Avoid compacted potting mix around the roots.
• Wintering: Keep bright, cool and frost-free where possible.
• Feeding: Feed during the growing period with citrus fertiliser. Long-term potted kumquats need regular feeding while leaves and fruit are developing.
• Air and humidity: Dry heated air can cause leaf drop and pests. Use humidity support if indoor air is very dry, and keep the plant in bright conditions with some air movement.
• Fruit balance: Let young plants build roots and branches before carrying a heavy crop. Remove excess fruit if a small plant looks strained.
• Repotting: Repot when the container is well rooted, moving up only one pot size. On established plants, refresh the top layer of potting mix between full repots.
• Pruning: Shape lightly after fruiting or before stronger growth. Remove crowded shoots and any growth from below the graft point, if your plant is grafted.

Pale leaves, fruit shrivel and winter leaf drop

• Small pale leaves: Check feeding, iron supply, root health and potting mix condition. Long-term potted kumquats can develop pale growth when feeding or root health is off.
• Winter leaf drop: Review light, watering and temperature swings. A bright, cool winter position helps reduce leaf drop.
• Shrivelled fruit: Check whether the rootball dried too far or watering has been uneven. Fruiting citrus needs moisture available through the full rootball.
• Sparse flowering: Sparse flowering is usually linked to weak winter light or plant age.
• Sticky residue on leaves: Inspect for scale, aphids or mealybug, especially where leaves meet stems.

Kumquat peel, pets and naming

Kumquat peel, leaves and stems contain citrus oils and psoralens. Remove fallen fruit, loose leaves and pruned stems where pets can reach them, and take care around small thorns during shaping or repotting.

The name kumquat comes from Cantonese and is commonly interpreted as golden orange or golden mandarin.