How to grow cumquat
Overview
Cumquat (Citrus japonica) is a compact evergreen citrus grown for its fragrant white flowers, glossy dark leaves, and small oval fruit. It is one of the few citrus that can be eaten whole, skin and all, making it both ornamental and productive in warm, sunny gardens.
Varieties
- Nagami — The standard oval cumquat, widely grown in Australia for its sweet skin and tart flesh.
- Marumi — Round, sweeter fruit with a thinner skin; less common but excellent for eating fresh.
- Meiwa — Large, round, very sweet fruit; ideal for home gardens in warm climates.
Soil Preparation
Cumquat prefers slightly acidic soil (pH 6.0–6.5) with good drainage. Before planting, incorporate 2–3 kg of well-rotted manure or compost per square metre. If soil is heavy clay, raise the bed or plant in a mound to prevent waterlogging.
Growing Guide
Plant cumquat in a sunny, sheltered spot with well-drained soil. Space trees 2–3 m apart; for pots, use a 40–50 cm container. Dig a hole twice the width of the root ball, backfill with compost and aged manure. Water deeply at planting, then every 7–10 days until established. Mulch with 5–7 cm of organic matter, keeping it clear of the trunk.
Sowing
Cumquat is rarely grown from seed; most plants are grafted onto rootstock. For seed, sow 1 cm deep in seed-raising mix, keep warm and moist, and expect germination in 2–4 weeks. Transplant seedlings after 1–2 years.
Care
Feed cumquat with a balanced citrus fertiliser (e.g., 13:5:13) in early spring and late summer. Prune lightly after harvest to shape the canopy and remove dead or crossing branches. Top-dress with compost in autumn and water during dry spells.
Companion Planting
Plant cumquat near marigolds, nasturtiums, and lavender to repel aphids and attract beneficial insects. Avoid planting near eucalypts or other citrus that host gall wasp. Keep a 1 m clear zone around the trunk for airflow.
Common Pests & Risks
Scale insects appear as brown bumps on stems and leaves; treat with horticultural oil in winter. Citrus leaf miner causes silvery tunnels on new leaves; control with neem oil or remove affected leaves. Citrus gall wasp creates lumps on branches; prune out galls in winter and dispose of them.
Harvesting
Harvest cumquats when the fruit is fully bright orange and yields slightly to pressure. The skin is sweet and the flesh tart; pick by clipping the stem to avoid damaging the tree. Fruit can be stored in the fridge for 2–3 weeks or preserved whole in syrup.
In the Kitchen
Cumquats are eaten whole: the skin is sweet, the flesh tart. Slice them into salads, use in marmalades, or candy them whole. They can also be preserved in syrup or used as a garnish for cocktails and desserts.
Troubleshooting
Yellow leaves: often caused by poor drainage or overwatering; check soil moisture and improve drainage. Brown leaf edges: usually from salt burn or dry air; mulch well and water deeply. Fruit drop: may be due to sudden temperature changes or inconsistent watering; maintain steady moisture. Stunted growth: check for citrus gall wasp or scale; treat as needed.