Plant of the Month – Ironwood

June 3, 2024

The spines on the ironwood provide a great defense against predators.

Desert Ironwood, Olneya tesota

Dense, thorny, and strong like steel, the Desert Ironwood Tree (Olneya tesota) is an under recognized super tree of the Sonoran Desert. It is naturally found along washes and hillsides of Arizona’s deserts under 3,000 ft of elevation. It offers valuable protection for understory plants and habitat for our native wildlife. When in their natural environment, these trees are unassuming and blend into the surroundings. They can get large for a desert tree at 25 x 25, but they are slow growers and can take on a shrub like multi trunk form.  In late spring you suddenly notice a light pink to purple hue, like a pastel cloud on silver branches. It is when in bloom that the Ironwood trees stand out and you realize they have been hiding in your local hiking spots the whole time.

“Take a deeper look at this Sonoran Desert super tree, the Ironwood. We will learn about what makes this tree special and how its vicious adaptations allow for cacti to thrive in its protective embrace.”

At closer inspection you will notice the wonderful metallic silver color to the young branches which surprisingly have short wicked thorns. Like any true desert plant worth their weight, the Ironwood has some defense against predators like voracious bunnies and zealous Gila Woodpeckers. If you’re a plant you have to get vicious to survive and thrive in the desert. Not only is the Ironwood tree loaded with stout spines, but the wood is incredibly dense! If you were to pick up a fallen branch you would be surprised at how heavy it is, it may even sink if placed in water (not common for wood). The trunk is resistant to rotting, and even if the tree dies the wood may remain intact for up to 1600 years. [reference Arizona-Sonora Desert Museum]

A mature tree offers dense shade.


A desert tree with unique characteristics and critical importance for Sonoran Desert ecology

If you have not been won over yet by this stalwart tree, I have more to tell! The Desert Ironwood is considered a keystone species in the Sonoran Desert for its ability to act as a nurse plant. Not only do these super trees increase the number of bird species in an area, but the understory of an Ironwood provides  even more critical services. It protects  protection from herbivores, heat and direct radiation, freezing night temperatures, and the soil beneath increases the chance of germination of succulents and cacti. That means our threatened or endangered cacti (saguaros🌵) rely on Ironwoods to ensure baby cacti have a chance.

Ironwood flowers and fruit occur in most years, but are typically abundant only four years per decade. It will depend on weather conditions.

Is Ironwood the tree for you?

Ironwood flower.
Pinkish-lavender pea-like flowers appear in May and June that are vital to pollinators.

Now if you think this all sounds wonderful, but what does that mean for my landscape, let’s walk through some pros and cons on if the Ironwood is the right tree for you.


  • They are slow growing, so if you need shade and a big tree right now, this may not be your tree
  • They are evergreen, but that means they do drop leaves throughout the year, especially right before they bloom, just not all at the same time
  • They eventually grow to a large tree (25 x 25) and need the room to grow
  • They do have thorns. As they grow larger the main trunk gets woodier and will not be as thorny, but the smaller newer branches will have attitude.


  • Dense heavy wood that is less prone to breakage
  • A wildlife powerhouse as it provides shelter, food, and nesting sites
  • Low water needs and a native tree
  • Lovely color and architectural addition to a landscape
  • Low maintenance- It’s a set it and forget it tree once it establishes a good root zone


If this is not the right tree for your yard, that is a great distinction to make before you plant one. However, the next time you are hiking and exploring in the desert, take a closer look at the trees and see if you can find the Ironwood tree hiding in plain sight.

You may be interested in this other related article:

Ironwood – the Desert’s Oldest Nurse

Did you know that up to 70 percent of water use is outdoors? That’s why we love desert plants and feature them each month. You can learn more about Ironwood and other plants on our Arizona Low-Water-Use Plants page. Visit our page on Choosing and Planting Low Water-Use Plants for tips on plant selection and how to plant properly. Also, be sure to read through all of our featured Plant of the Month blogs!

Victoria Castor is a Sustainability and Water Conservation Coordinator with the City of Peoria, AZ, one of 19 Water– Use It Wisely partners to offer water-saving advice and programs. Victoria is a Master Gardener and overall nature aficionado. Being a Arizona native, she sees the shift and need locally to educate and help people embrace our unique desert.