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Growing Kumquats: Citrus japonica

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Members of the Rue family, Kumquats are more cold hardy than other citrus and have smaller fruit. Also, their fruit rind is lacking citric acid, which makes the rind sweet and edible, but provides less protection against insects.

Form: Tree.
Lifespan: Productivity up to 50 years in 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 species and 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. Seeds are a source of pectin.
Months for fruit to ripen: 6, depending on cultivar and micro-climate. Ripe when fully orange with no trace of green. Does not ripen 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. This is normal, and can be considered as the plant's way of going semi-dormant in the winter, as an alternative to dropping leaves. When temperatures warm back up in the spring, the leaves will green up.
Stems: Few or no thorns. Densely branched. Bark is prone to sunscald if not shaded by leaves, especially in higher temperatures.
Roots: Usually grafted on Trifoliate Orange (Poncirus trifoliata) rootstock because its own roots do not allow it to flourish.
Species of Note:
C. japonica 'margarita': Oval / 'Nagami' Kumquat - oval shape with sweet rind and tart pulp, unique sweet-sour flavor, eaten whole, about 1" diameter. 'Nordmann Seedless' is a variation.
C. japonica 'crassifolia': Large Round / 'Meiwa' Kumquat - nearly round shape, sweet thick rind and pulp, sweetest tasting, 1.5" diameter.
C. japonica 'obovata': 'Fukushu' / 'Changshou' Kumquat - oval with depressed apex, 1-1.5" long, sweet rind and tart pulp, thornless, spreading dwarf tree with larger leaves, 6-10' tall, less cold hardy, a hybrid, possibly kumquat-mandarin.
C. japonica 'Marumi': Round / 'Marumi' Kumquat - round shape, sweet rind and pulp, intermediate sweetness between Nagami and Meiwa, 1" diameter, flesh can be dry.
C. japonica 'hindsii': 'Hong Kong' Kumquat - a wild, bitter tasting, thorny ornamental.
Wildlife: Attracts bees, butterflies, birds.
Toxic / Danger: Possible thorns.
Origin: China and southeast Asia.

Cultivation and Uses
USDA hardiness zones: 8b-11.
Chill hours: None.
Heat tolerant: Less than other citrus members.
Sun: In very hot climates, afternoon shade is necessary to reduce heat and water stress. Avoid reflected heat.
Drought tolerant: Yes.
Water after becoming established: Every one or two weeks in winter. Deep water twice a week to maintain fruit crop. Allow soil to dry out between waterings. May need water more often in extreme heat.
Soil: Well drained, tolerate of soil types, but a plant-based soil amendment without fertilizer improves performance, pH 5.6-7.5 (acidic to neutral) for best results.
Fertilize: Do not fertilize the first year. Kumquat should be given one-half of the total annual fertilizer amount used for other citrus trees, in three doses. Apply a citrus fertilizer with citrus micronutrients, end of January, end of March, and end of August, using one-sixth of the annual recommended amount for citrus in each dose. Follow directions on package. Or, if using organic fertilizer, apply every month from mid-February to late September. Do not fertilize after September to keep the plant from producing new growth that will be harmed by early frost.
Kumquat trees are small and grow slowly, so they need less fertilizer than most citrus trees. These trees 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 three times a year is helpful.
Mulch: With organic material all year to reduce water loss and reduce heat and cold stress. Keep mulch one foot away from trunk.
Planting: Can be grown in large containers and indoors near a large, south-facing window in cold climates. Outdoors add a good quality soil amendment without fertilizer to soils low in organic content.
First Year Care: Do not fertilize. Water at least twice a week, but do not overwater. Soil must dry out between waterings.
Prune: Remove any suckers growing from the base of the tree. Remove crossing branches and shape in winter. If you prune up from the bottom to expose the trunk, you should paint the trunk with a white interior latex, diluted by half with water, to avoid sunscald.
Litter: Fruit drop.
Propagation: Cuttings grafted onto special rootstock. Seed does not grow true and often has low viability.
Pests: Giant Swallowtail Butterfly caterpillar. This larvae 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.
See Citrus: Diseases and Disorders
Uses: Ornamental, edible fruit, jams, marmalade.

Former botanical name: Fortunella. The fruit may need to be sprayed with a garlic and Habanero pepper mix to keep insects away.

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Kumquat: Citrus japonica - flowers

Kumquat: Citrus japonica - fruit

Kumquat: Citrus japonica
Citrus japonica var. margarita: Oval / 'Nagami' Kumquat

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