Garden Oracle / Drought and Heat Tolerant Gardening / Tucson - Phoenix - Arizona - California

Growing Pecan:
Carya illinoinensis

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Botanical Overview

A member of the Walnut family (Juglandaceae), the Hickory genus (Carya) has 27 species of deciduous nut trees. Carya illinoinensis, grown for its edible seed, is known as Pecan.

Description

Form: Tree.
Lifespan: 300 productive years.
Leaf retention: Deciduous.
Growth rate: Slow to moderate.
Mature Size: 50-130' high and as wide.
Flowers: Separate male and female flowers are present on the same tree. Male flowers are drooping catkins and develop at the end of last year's wood. Female flowers are short green erect spikes appearing at the end of new growth.
Bloom: Early spring. Pecan flowers can be damaged by late frosts, eliminating or substantially reducing the crop for that year.
Pecan trees are alternate bearing, producing a heavy crop one year followed by a light crop the next.
Self-fruitful: Depends on cultivar. Pecan trees are wind pollinated and fall into two cultivar groups. Type 1 (protandrous): male flowers open before female flowers become receptive, and Type 2 (protogynous): male flowers open after female flowers become receptive. For most cultivars, both a type 1 and a type 2 are needed for an abundant crop.
Years before fruiting: 5-10 for grafted trees, 10-15 ungrafted.
Fruit: A green, thin-fleshed, four-segmented husk covers a thin, hard, oblong shell (the endocarp) enclosing a seed called the pecan nut. When the seed is fully ripe, the husk turns brown and splits off the shell, allowing it to drop to the ground. Fruit that falls before becoming fully ripe is due to an overly heavy crop, or insufficient deep watering in previous months.
Months for fruit to ripen: Six.
Storage after harvest: Pecans must be quickly dried to 4.5% moisture before storage. Dried pecans may be refrigerated 1-2 years in a sealed container, with nuts in the shell lasting longer than shelled nuts.
Leaves: Green, compound leaves with 9-17 lance-shaped leaflets.
Stems: No thorns. The bark is shaggy and shedding. Pecan branches may suddenly fall in summer if they receive too much shade and not enough sun. Heavy fruit loads will also cause old limbs to break off and fall.
Roots: Pecans are grown on rootstock selected for local soil and climate. In Arizona, rootstocks from New Mexico are used because California rootstocks are not well suited to the climate. The roots may be 4-5 times wider than the height of the tree, but usually no more than 4-5' deep.
Wildlife: The flowers may attract non-pollinating insects. The seeds attract mammals and birds.
Toxic / Danger: Walnut family members produce the poison juglone, but pecan trees produce only small quantities. The tiny amount of juglone in pecan seeds usually does not bother animals but may cause gastric upset in dogs or laminitis in horses if eaten in sufficient quantities. Juglone produced by roots can cause harm to some species of plants growing nearby, such as apples, potatoes, and blackberries, that may need to be moved in favor of more juglone-tolerant plants. Pecan leaves are safe to compost.
Origin: The Mississippi river flood plain states plus river bottoms in Oklahoma, Texas, Kansas, and small parts of northern Mexico.

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Cultivation and Uses

USDA hardiness zones: 6-9
Chill hours: 100-600 depending on cultivar. While budbreak may happen after a low chill winter, pollination problems are likely.
Heat tolerant: Yes, with regular irrigation.
Drought tolerant: No.
Sun: Full sun.
Planting: Locate this eventually-to-be-huge tree in full sun, at least 40' from any structure, wall, or other large plant. Pecans need good air circulation in their branches. Plant pecan trees mid to late winter, removing any caliche from the area first.
Avoid placing a pecan tree near where cars park. In the fall, aphids feeding on sap from the leaves will drop a sugary residue on the ground underneath the tree.
Soil: Well drained. Pecans do best in soils that are pH 6-7 (slightly acidic to neutral), but can tolerate a wider range of soils as long as they drain well. They are not salt tolerant.
Fertilize: In the southwestern United States, zinc and nitrogen deficiency is common in pecan trees. Nitrogen should be applied just before budbreak to the soil in the form of nitrogen sulphate, ammonium phosphate, or urea. Avoid adding too much nitrogen to smaller trees because that will inhibit nut production. Zinc sulfate should also be included in the mix. The signs of zinc deficiency are small leaves with brown patches and shortened leaflets. Zinc should also be sprayed on the foliage using a solution of zinc sulfate and ammonium sulfate when new leaves have reached two inches in the spring, then every two weeks thereafter for a total of six applications. Wet the leaves thoroughly.
Water after becoming established: Pecan trees are native to the Mississippi river region and need regular water. Use basin or flood irrigation every week mid-spring to mid-fall, and every two weeks at other times. The soil should dry out 2-3" on top, before watering again, but must always be moist below the surface. The water must be low in dissolved salts.
Mulch: Spread organic mulch inside the drip line and 8" away from the trunk to reduce soil evaporation.
First Year Care: After planting a dormant tree, cut back all branches by one-third. Then, after the branches have grown six inches, select one to be the central leader and cut back the others.
Prune: Prune pecan trees mid winter. Remove any dead or crossing branches and branches growing inward. The branches should be spaced to allow air to flow easily within the entire structure once leafed out.
Litter: Leaves in early winter. Nuts may drop at various stages of maturity depending on the cultivar.
Propagation: Grafted cuttings.
Uses: Edible nuts, shade.

Comments

The pecan becomes a huge tree needing a large amount of water and a vast area. In a residential setting of the southwestern United States, it does best in a yard that can be periodically flooded. Most cultivars need both a type 1 and a type 2 tree to produce nuts.
Macadamia and Almond are nut trees better suited to hot, dry climates.



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By Pmg - Own work, CC BY-SA 3.0, httpscommons.wikimedia.orgwindex.phpcurid-2206710
Male catkins

By Brad Haire, University of Georgia, #5007031 at Forestry Images, operated by The Bugwood Network at the University of Georgia and the USDA Forest Service

By UserSeqqis - Own work, CC BY-SA 3.0, httpscommons.wikimedia.orgwindex.phpcurid-26486472


Latest update: July, 2024
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