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

Growing Olneya tesota:
Desert Ironwood

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Form: A single to multi-stemmed shrub, or with pruning, a tree.
Lifespan: 50-150 years.
Leaf retention: Evergreen except will it will drop its leaves under three conditions: before blooming (which does not happen every year), extreme drought, and cold temperatures below its hardiness range.
Growth rate: Slow. Supplemental water speeds growth.
Mature Size: 15-30' high and as 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: Spring, after its leaves have dropped. This plant usually blooms less than once every five years.
Fruit: A short brown seed pod. The pea-sized black seeds are edible only after roasting.
Leaves: Tiny, oval, thick, green to bluish-green, paired leaflets. Each compound leaf has a 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: The flowers attract bees, the seed pods attract birds, and the leaves are browsed by large mammals. This plant provides shade to smaller plants and many animals in the desert.
Toxic / Danger: Thorns. The wood contains toxins; sawdust is a possible breathing hazard.
Origin: California, Arizona, and 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. Trim to maintain a balanced shape, when young. In the wild, these trees sometimes grow awkwardly unbalanced.
Litter: Leaf drop, which is prevented by monthly watering during drought.
Propagation: Seed.
Uses: Ornamental, xeric garden.

This plant is a member of the Legume family (Fabaceae). It is a protected species and long lived — some specimens are centuries old. A few commercial varieties have been selected for improved cold hardiness.
The overall appearance of this tree in full bloom, with pale pinkish blossoms, is very subdued.

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Olneya tesota: Desert Ironwood - flowers

Olneya tesota: Desert Ironwood - seed pods

Olneya tesota: Desert Ironwood - seed in pod

Olneya tesota: Desert Ironwood - leaves

Olneya tesota: Desert Ironwood - tree

Latest update: July, 2021
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