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Growing Mandarin Oranges / Tangerines: Citrus reticulata

Botanical Overview

Members of the Citrus family (Rutaceae), modern Citrus fruits, according to genetic analysis, are complex hybrids arising from mandarin, pomelo, and citron ancestors, refined by more than four thousand years of cultivation. Mandarins, known for their thin, loose peels and sweet flavor, are often classified into groups based on where they were developed, such as Mediterranean, King (Indonesia and the Philippines) and Satsuma (Japan). There are hundreds, if not thousands of mandarin cultivars. The word Tangerine, originally designating mandarins from Tangiers, Morocco, is used now to describe all Mandarins or just selected cultivars.

Description

Form: Tree.
Lifespan: 20-30 productive years.
Leaf retention: Evergreen.
Growth rate: Moderate.
Mature Size: To 25' high and as wide without a dwarfing rootstock.
Flowers: Five narrow, white petals, long white, yellow-tipped stamens, fragrant, from red-tinged buds.
Bloom: Late winter and/or spring. Some cultivars tend to bloom more in alternate years.
Self-fruitful: Some are self-pollinating, except for Clementine and Minneola which need a second compatible cultivar nearby for pollination.
Years before fruiting: 3-4 for trees with grafted rootstocks.
Fruit: Orange in color, with a thin peel which is often loose or easily removed. Mandarins are smaller and less round, sweeter, less acidic and have a stronger flavor than the typical orange.
Months for fruit to ripen: 12. Mandarins do not ripen further once picked and must be left on the tree until ripe. Some cultivars must be fully colored to be ripe, others can be light green. To tell if the fruit are ripe, one must be removed from the tree and tasted. It is ripe when sweet. If sour, they need to stay on the tree longer. Rainfall, sunlight, and temperature determine ripening times and will vary from year to year. Leaving the fruit on the tree after ripening will cause it to become sweeter as the acidity is reduced.
Remove fruit from the tree using clippers, cutting the stem close to the fruit. Pulling a fruit from the stem will tear a gap in the loose skin.
Storage after harvest: Mandarins can be refrigerated up to six weeks. They can be kept at room temperature one week.
Leaves: Dark green, glossy, lance-shaped.
Stems: Slender, sometimes thorny.
Roots: These trees are grafted onto rootstock that is used to control the height of the tree from dwarf, to semi-dwarf, to standard. The part of the tree above the graft, called the scion, is selected for its desirable fruit. The rootstock is from a hardier species which commonly has less tasty fruit.
Cultivars of Note:
'Clementine' a small hybrid of mandarin and sweet orange, seedless unless cross-pollinated, easy to peel.
'Gold Nugget' seedless, moderately easy to peel, the fruit matures mid-March and stores well on tree up to summer, a fairly vigorous, medium-sized tree.
'Tango' seedless, moderately easy to peel, the fruit matures in January and stores well on the tree but should be harvested before blooming begins. The tree is fairly vigorous and medium-sized. Thinning of young fruit is required to avoid alternate-bearing.
'W. Murcott' few seeds unless cross-pollinated, easy to peel, a medium-sized tree, susceptible to alternate-bearing, handles heat well. 'W. Murcott' is very different from 'Murcott'.
Wildlife: The flowers attract bees and insects. The fruit attracts birds. This tree is a food plant for the Giant Swallowtail butterfly caterpillar – see Pests, below. Mammals may strip the bark off of young trees, consume fallen fruit, or climb the tree to eat the fruit.
Toxic / Danger: Thorns on some cultivars.
Origin: Asia.

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Mandarin Orange / Tangerine: Citrus reticulata - flowers

Mandarin Orange / Tangerine: Citrus reticulata - fruit

Cultivation and Uses

USDA hardiness zones: 9-11.
Chill hours: None.
Heat tolerant: Yes, except for Satsuma cultivars which are unsuitable for high temperatures.
Drought tolerant: Somewhat, after three years, but not without damage to the fruit crop.
Sun: Full sun with afternoon shade when temperatures are over 90°F.
Planting: The best time to plant a citrus tree is after the danger of frost is past, in late winter or early spring.
Place mandarin trees in a sunny location, with afternoon shade, away from the coldest part of the yard, and out of the wind. Do not position the plant next to a frequently watered location, such as grass. Make sure there is enough space for the tree to grow to its full width and height, with clearance to walk around and where overhead lines will not be a problem.
Dig a hole twice as wide as the rootball, with the root crown at 1-2" above ground level. The top roots must extend out from the trunk, just above, and uncovered by, soil. The soil should slope gently downward from the trunk to the drip line.
Mandarin trees can be grown in containers.
Soil: Well drained to prevent root rot. Do not amend the soil when planting. The roots will adjust to the native soil surrounding the planting hole.
Fertilize: Apply an organic fertilizer every month or two from mid-February to early October. Alkaline soils will cause iron deficiency. Apply a citrus micronutrient solution as necessary when leaves become yellow with green veins, signalling a micronutrient deficiency. Only use products containing iron in chelated iron form, which is more easily absorbed by the plant. Avoid chemical fertilizers because they increase salt build-up in the soil. Do not fertilize after September to keep the plant from producing new growth that will be harmed by early frost.
Water after becoming established: Basin irrigate or deep water for 1.5 hours or more until the water has reached a 3' depth. The frequency of irrigation depends on the species, the age of the tree and the month of the year. For trees in the ground three years or more, irrigate as follows: December-February, every 21-30 days; March-April, every 14-21 days; May-June, every 14 days; July-September, every 10-14 days; October-November, every 14-21 days.
Inward leaf curling, when the leaves are uniformly green, or drooping leaves, are signs of insufficient water. Solid yellow leaves are a sign of overwatering. Do not water at the trunk but near the drip line.
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. Place a rodent gnaw guard around the trunk at the bottom.
First Year Care: Remove all fruit, if any, when first planted. Remove all fruit developing in the first three years so the plant will direct its energy to growing roots, branches and leaves. Water at planting, then for the first month, every 2-3 days; for months 2-3, every 3-5 days; from four months on, water according to temperature, from every 2-5 days July-September to every 14 days December-February.
Prune: Prune only after danger of the last frost is over in late winter or early spring. Flower buds develop during the winter dormant period, so pruning after the last frost makes it possible to avoid excess flower removal.
Citrus trees are best grown as shrubs, so that leafy branches protect their entire trunk from direct sun. Only prune the lowest branches if their tips touch the ground. If you prune up from the bottom to expose the trunk, you must paint it with a tree trunk paint to avoid sunscald.
Remove branches that are dead, damaged, diseased, or malformed. Remove any branches growing less than 45° from the vertical because they may split away as they get larger. Remove any new branches that have an angled cross section (malformed) rather than round. These have restricted veins and will not fruit well. Remove any branches growing from below the trunk graft as they occur. These are rootstock branches, not fruiting stock branches, and will produce inferior fruit.
Never prune to restrict the size of a citrus tree. Rootstocks are used to control the size of these trees.
Remove grass and other plants under the canopy that can compete for water and nutrients by hand-pulling, not with tools that can damage roots close to the surface.
Litter: Leaves throughout the year, mostly during flowering. Flower and fruit drop in spring and summer as the tree self-regulates the number of fruit it can bear.
Propagation: Seed, cuttings.
Pests: The Giant Swallowtail Butterfly caterpillar 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.
Leaf wrinkling in the summer may be due to thrips or heat. Thrips do no real damage. They are attracted to plants that are given too much nitrogen or are overwatered. If you do not see scars on the leaf, it is probably due to heat, and watering should be increased. This form of leaf wrinkling is most often found on Mandarins as opposed to other citrus. See Citrus: Diseases and Disorders
Uses: Edible fruit, ornamental, shade.

Comments

Seedless cultivars are available.


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Latest update: October, 2020