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Olneya tesota

desert ironwood

Fabaceae Sonoran Desert

Attracts Pollinators Attracts Butterflies Drought Tolerant

Native to North America

SunFull Sun

WaterVery Low · drought-tolerant

HardinessZones 9–11

Overview

Olneya tesota is a slow-growing, evergreen to drought-deciduous tree in the pea family, and the only species in its genus. It is native to the Sonoran Desert of Arizona, southeastern California, and northwestern Mexico, where it is a dominant tree of desert washes and bajadas. Mature trees reach 15-30 feet (4.5-9 m) tall and about as wide, with a dense, rounded crown and gray, fissured bark. The gray-green leaves are pinnately compound with small oval leaflets, and a pair of short, curved spines sits at the base of each leaf. In late spring it carries clusters of pea-like flowers in pale lavender-pink to white, about 0.5 inch (12 mm) long. Flat seed pods follow, holding shiny brown seeds that were a food source for Indigenous peoples. The wood is extremely dense and heavy, sinking in water, and the tree can live for several centuries. It grows very slowly, is damaged by hard frost when young, and casts dense shade that shelters seedlings of other desert plants beneath it.

Native Range

Native to the Sonoran Desert of southern Arizona, southeastern California, and northwestern Mexico, including Sonora and the Baja California peninsula, along desert washes, arroyos, and rocky slopes below about 2,500 feet (760 m).

Suggested Uses

Used as a drought-tolerant shade or specimen tree in desert and xeriscape gardens, spaced well away from structures for its broad crown. It supplies cover, nectar, and seed for desert wildlife and shelters tender seedlings as a nurse plant. The dense canopy gives filtered shade for understory desert plantings.

How to Identify

Identify Olneya tesota by its dense, rounded crown of gray-green pinnately compound leaves, each guarded by a pair of short curved spines at the base. The bark is gray and fissured, not green like the palo verdes it grows among. In late spring it bears clusters of pale lavender-pink pea flowers, followed by flat, constricted seed pods.

Appearance

Size & Dimensions

Height15' - 30'

Width/Spread15' - 30'

Reaches mature size in approximately 30 years

Colors

Flower Colors

Foliage Colors

Fall Foliage Colors

Bloom Information

Bloom Period

~4 weeks

Spring Summer

Flowering occurs in late spring, mainly May into June. Short clusters of pale lavender-pink to whitish pea flowers open across the crown over two to three weeks. Flat pods ripen through early summer and split to drop shiny brown seeds.

Detailed Descriptions

Flower Description

pale lavender-pink to white

Foliage Description

gray-green

Growing Conditions

Sun Requirements

SunFull Sun

Requires 8-12 hours of direct sunlight daily

• Full Sun: 6+ hours of direct sunlight

• Partial Shade: 3-6 hours of direct sunlight

• Full Shade: Less than 3 hours of direct sunlight

Soil Requirements

pH Range7.0 - 8.5(Alkaline)

357912

Soil Types

sand rocky loam

Drainagewell drained

Water & Climate

Water Needs

Very Low

Frost Tolerance

tender

Time to Maturity

10-15 years

Drought Tolerance

Drought tolerant when established

Care & Maintenance

Care Guide

Grows in full sun in hot, low-desert conditions on sandy, gravelly, or rocky soils with sharp drainage. It is highly drought tolerant once established and needs only occasional deep watering in extreme heat. Alkaline desert soils with a pH of 7.0 to 8.5 suit it. Young trees are damaged by hard frost and grow slowly, so they need a warm, sheltered position for the first few years. Established trees have few pest or disease problems. Propagation is by scarified seed, which germinates quickly in warm soil.

Pruning

Light structural pruning to establish a single or multiple trunk is done on young trees in the dry, frost-free season. Mature trees need only the removal of dead or crossing branches. Heavy cuts are avoided because the slow growth is slow to mask them.