Gardening
in Tucson, Phoenix,
Arizona and California

Gardening in Tucson, Phoenix, Arizona and California

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Olneya tesota: Desert Ironwood

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Description
Form: A single to multi-stemmed shrub, or with pruning, a tree.
Leaf retention: Evergreen except will it will drop its leaves under three conditions: before blooming (only in some years), extreme drought, and cold temperatures below its hardiness range.
Growth rate: Slow. Supplemental water speeds growth.
Mature Size: 15-30' high and 15-25' wide.
Flowers: Pea-flower shaped, light purple wing petals with other petals being white or pink, clustered on short shoots that grow from the middle of stems.
Bloom: In spring after leaves have dropped, but blooms less than half of all years in total.
Fruit: Hairy, brown seed pod. Seeds are edible only after roasting.
Leaves: Tiny, oval, thick, bluish gray-green, paired leaflets. Each compound leaf has pair of thorns at its base. This plant provides medium shade.
Stems: Thorny. The wood is dense, heavy, sinks in water, and contains chemicals toxic to wood-rotting microbes.
Roots: Nitrogen-fixing*.
Wildlife: Attracts bees, birds, browsed by large mammals. It provides shade to smaller plants and many animals in the desert.
Toxic / Danger: Thorns. Chemical-laden dust from wood cutting is a possible breathing hazard.
Origin: California, Arizona, Mexico.

Cultivation and Uses
USDA hardiness zones: 9-11. Young trees are hardy to 25°F, older ones to 20°F.
Heat tolerant: Yes.
Drought tolerant: Yes.
Sun: Full sun.
Water after becoming established: Once every month or two during drought.
Soil: Well drained, dry, low in organic content, pH 6.6-8.5 (neutral to alkaline). *Do not use a nitrogen fertilizer.
Prune: Clip lightly to shape and thin.
Litter: Leaf drop; prevented by monthly watering during drought.
Propagation: Seed.
Uses: Ornamental, shade, xeric garden.

Comments
This plant is a protected species and is very long lived — some specimens are centuries old. A few commercial varieties have been selected for improved cold hardiness.



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By Ken Bosma from Tucson, Arizona, USA - Iron Wood, CC BY 2.0, httpscommons.wikimedia.orgwindex.phpcurid-20666566

Olneya tesota: Desert Ironwood - leaves

Olneya tesota: Desert Ironwood - tree