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in Tucson, Phoenix,
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Growing Kumquats: Citrus japonica

Botanical Overview

Members of the Citrus family (Rutaceae) and Citrus genus, Kumquats are more cold hardy than most cultivated citrus and have smaller fruit. The fruit rind is lacking citric acid, which makes it sweet and edible, but provides less protection against insects.

Description

Form: A shrub.
Lifespan: Productive up to 50 years in a good location with proper care.
Leaf retention: Evergreen.
Growth rate: Slow.
Mature Size: 8-25' high and as wide.
Flowers: White, five petals, sweetly fragrant, borne singly or in a cluster of three or four.
Bloom: Mid spring into fall, or throughout the year in regions without freezes.
Self-fruitful: All Kumquat cultivars self-pollinate.
Years before fruiting: 3 years after grafting.
Fruit: Oval or round, golden yellow to reddish orange, 1" to 1.5" diameter, sweet edible rind, tart to sweet flesh, entire fruit, except seeds are eaten. The seeds are a source of pectin.
Months for fruit to ripen: 6, depending on cultivar and micro-climate. The fruit are ripe when fully orange with no trace of green. They do not ripen further after harvest.
Storage after harvest: At room temperature up to 3 days, or refrigerate up to 2 weeks.
Leaves: Glossy green, ovate. Citrus leaves have a tendency to turn pale-green or yellow in cold weather. When temperatures warm back up in the spring, the leaves will green up.
Stems: Few or no thorns. Densely branched. The bark is prone to sunscald if not shaded by leaves or covered by tree trunk paint, especially in higher temperatures.
Roots: Usually grafted on Trifoliate Orange (Citrus trifoliata) rootstock because its own roots do not allow it to flourish.
Cultivars of Note:
'Meiwa' - nearly round shape, sweet thick rind and pulp, sweetest tasting, 1.5" diameter.
'Nagami' - oval shape with sweet rind and tart pulp, unique sweet-sour flavor, eaten whole, about 1" diameter. This cultivar is more vigorous and hardy than others and grows faster. 'Nordmann Seedless' is a variation.
'Marumi' - round shape, sweet rind and pulp, intermediate sweetness between Nagami and Meiwa, 1" diameter, flesh can be dry.
'Fukushu' / 'Changshou' - a hybrid, possibly kumquat-mandarin, less cold hardy, oval with depressed apex, 1-1.5" long, sweet rind and tart pulp, thornless, spreading dwarf tree with larger leaves, 6-10' tall.
Wildlife: Attracts bees, insects, birds, and is a food plant for the Giant Swallowtail butterfly caterpillar – see Pests, below. Mammals may strip the bark off of young shrubs, consume fallen fruit, or climb the shrub to eat the fruit.
Toxic / Danger: Possible thorns.
Origin: Asia.

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Cultivation and Uses

USDA hardiness zones: 8b-11.
Chill hours: None.
Heat tolerant: Less than other citrus members.
Drought tolerant: Yes.
Sun: In very hot climates, afternoon shade is necessary to reduce heat and water stress. Avoid reflected heat.
Planting: Place the shrub in a sunny location with afternoon shade. Do not position it next to a frequently watered location, such as grass. Make sure there is enough space for the shrub to grow to its full width and height.
The best time to plant is after the danger of frost is past, in late winter or early spring.
Plant the shrub so that the root crown is at least one inch above ground level. The top roots must extend out from the trunk, just above, and uncovered by, soil. Kumquat can be grown in large containers. Indoors, in cold climates, the shrub should be placed near a large, south-facing window.
Soil: Well drained, tolerate of soil types, pH 5.6-7.5 (acidic to neutral) for best results.
Fertilize: Never use an NPK chemical fertilizer in desert soil, to avoid salt buildup. Apply an organic fertilizer, starting three months after planting, every month from mid-February to late September. Apply citrus micronutrients in irrigation water three times a year in February, May, and August. Do not fertilize after September to keep the plant from producing new growth that will be harmed by early frost.
Kumquat shrubs are small and grow slowly, so they need less fertilizer than most citrus trees. These shrubs are prone to zinc deficiency, signaled by smaller leaves, reduced shoot length and possibly yellow blotches between green leaf veins, so application of citrus micronutrients is necessary.
Water after becoming established: Every one or two weeks minimum. Deep water twice a week to maintain the fruit crop. Allow the soil to dry out between waterings. Water may be needed more often in extreme heat. Inward leaf curling, when the leaves are uniformly green, is a sign of insufficient water.
Mulch: Apply organic mulch inside the drip line and 8" away from the trunk to reduce soil evaporation and reduce root zone heat and cold stress.
First Year Care: Water at least twice a week, but do not overwater. The soil must dry out between waterings.
Prune: Remove any suckers growing from below the graft on the trunk. Remove crossing branches and shape in winter. If pruning up from the bottom to expose the trunk, the trunk should be painted with tree paint to avoid sunscald.
Litter: Fruit drop.
Propagation: Cuttings grafted onto special rootstock. Rooted cuttings have very weak roots that do not allow the plant to thrive, although they might do well in a container. Some, but not all, varieties of kumquat seed may grow true to their parents.
Pests: The caterpillar of the Giant Swallowtail Butterfly resembles bird poop and has white and black and/or brown splotches. On a large plant it will cause no harm. On a small plant, relocate it to a large citrus. The fruit may need to be sprayed with a garlic and Habanero pepper mix to keep insects away. See Citrus: Diseases and Disorders
Uses: Ornamental, edible fruit, jams, marmalade.

Comments

Former scientific name: Fortunella.


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Kumquat: Citrus japonica - fruit

Kumquat: Citrus japonica
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Latest update: June, 2020