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in Tucson, Phoenix,
Arizona and California

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Growing Limes: Citrus aurantiifolia etc.

Botanical Overview

Citrus fruits called Limes are members of the Citrus family (Rutaceae) and Citrus genus. According to genetic analysis, Limes are complex hybrids arising from mandarin, pomelo, citron and hystrix ancestors, refined by thousands of years of cultivation. Key Lime, for example, is a cross of Citrus hystrix with citron. Persian Lime, in turn, is Key lime crossed with Lemon. Australian Finger Lime, the exception, is related to kumquat, but not C. hystrix.
Several citrus species and hybrids are called Lime because of their flavor. A few are in commercial production or sold by nurseries for residential use.

Description

Form: A shrub or small tree.
Lifespan: 50-150 years, with the first 50 being the most productive.
Leaf retention: Evergreen.
Growth rate: Moderate to fast.
Mature Size: Citrus aurantiifolia: 12-16' high and as wide.
Flowers: White, five petals, fragrant to scentless. Reddish buds.
Bloom: Depends on cultivar. Often spring through fall, possibly all year in regions without freezes.
Self-fruitful: All lime cultivars self-pollinate.
Years before fruiting: Grafted: 3-6. Cuttings and air layers: 1 year after planting. Seed: 4-8 years after planting. Remove all small fruit in the first 3-5 years to speed growth of roots, stems and leaves.
Fruit: Round to oval, sometimes with a nipple at the blossom end.
Months for fruit to ripen: 5-6 after flowering. Limes are picked green commercially, but most are mature when the skin is light green or pale yellow.
Storage after harvest: 6-8 weeks in refrigeration.
Leaves: Oval to lance-shaped, glossy green, slightly fragrant.
Stems: Thorny to thornless depending on cultivar.
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.
Species / Cultivars of Note:
Citrus australasica: Australian Finger Lime – cylindrical fruit filled with fleshy, round vesicles, fewer, separate seeds, and an enjoyable lime-like flavor. Hybrids with other citrus species have produced a variety of rind colors, including red. This species is known as lime caviar because the flesh is made up of small, round, thin-skinned drops. The tree has noticeably smaller leaves.
Citrus x latifolia: Bearss / Persian Lime – larger, oval fruit, seedless, dark green to light green at maturity, milder flavor, grown commercially;
Citrus aurantiifolia: Sweet / Palestinian Sweet Lime – lemon-sized fruit, light green to yellow at maturity, refreshing sweet juice lacks acidity (sourness);
Citrus aurantiifolia: Key / Mexican Lime – Very frost sensitive, small round fruit, the standard for lime flavor, yellow at maturity, limited commercial production;
Citrus aurantiifolia x japonica: Limequat – a small hybrid of kumquat and Key lime, with a lime-like flavor, somewhat more cold hardy than Key lime but not as hardy as kumquat. The rind is sweet and edible. Many consider this highly productive plant to be the best residential lime;
Citrus hystrix: Thai / Makrut Lime – its fragrant leaves are used in Asian cooking. The fruit of this ancestral species has bumpy green to yellow rind used in Asian curry and Creole cuisine, and unpalatable fruit juice used in shampoos and believed to kill head lice.
Wildlife: The flowers attract bees and other pollinating insects, and the leaves are food 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: For some cultivars, exposure to the rind oil or tree sap, and sunlight, causes dermatitis in sensitive individuals. Possible thorns.
Origin: Asia.

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Cultivation and Uses

USDA hardiness zones: 8b-10 for Limequat; 9b-11 for Persian Lime and Sweet Lime; 10-11 for Key Lime and Finger Lime.
Chill hours: None.
Heat tolerant: Yes.
Drought tolerant: Depends on rootstock. Drought will damage the fruit crop.
Sun: Full sun with afternoon shade, except for Finger Lime which is an understory shrub or small tree that needs shade most of the day in hot climates.
Planting: The best time to plant a citrus tree is after the danger of frost is past, in late winter or early spring.
Place limes trees in a sunny location, with afternoon shade, away from the coldest part of the yard, and out of the wind. Finger Lime, the exception, needs part shade most of the day. 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.
Lime 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 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. Water near the drip line, not at the trunk.
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: 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: Low. Fruit if not harvested.
Propagation: Cuttings grafted onto rootstock. The seed of Key Lime grows true, other cultivars may not, and may be sterile.
Pests: The Giant Swallowtail Butterfly caterpillar 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.
Distorted leaf shapes are a sign of thrips, which do no real damage. They are attracted to plants that are given too much nitrogen or are overwatered.
For other problems, see Citrus: Diseases and Disorders
Uses: Fruit, ornamental, shade.

Comments

This website uses World Flora Online as the definitive source for plant species names.


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Sweet Lime: Citrus aurantiifolia - flower

Sweet Lime: Citrus aurantiifolia - fruit

Sweet Lime: Citrus aurantiifolia
Citrus aurantiifolia: Sweet / Palestinian Sweet Lime - flowers, fruit and plant.


Makrut Lime: Citrus hystrix - fruit
Citrus hystrix: Thai / Makrut Lime


Limequat: Citrus aurantifolia x japonica - fruit
Citrus aurantiifolia x japonica: Limequat


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Latest update: October, 2020