Seed of the Week: Ironwood Tree

Our mystery seeds from last week came from the ironwood tree, Olneya tesota.

This unique tree gets its common name from the extreme hardness of its wood. Because there are a number of other trees with the same common name, it is sometimes called desert ironwood.

Desert ironwood is a small, shrubby tree found throughout the Sonoran Desert. The lower branches droop, giving a lovely form in its natural state.

The bark of the younger trunks and branches are pale gray to green at the tips.

It is a legume, having compound leaves of narrow, elliptical leaflets.

As with many desert plants, it is well armed, with many pairs of curved spines.

Desert ironwoods produce many lovely purplish-pink flowers in the spring. See Firefly Forest for a photograph of ironwood flowers.

The seed pods mature on the plant and then fall off.

The clue I mentioned that you might have noticed in the the mystery seed photograph last week was a drying leaf toward the bottom of the shot.

You can grow new trees from these seeds, but people often chose to purchase larger trees because desert ironwoods are very slow growing.

If you travel through the low desert you will often see dead ironwood trees. That is because the wood contains strong chemicals that prevent decay after the tree has died and the wood remains in place, sometimes for hundreds of years.

For more detail, see Natural History of the Desert Ironwood Tree (Olneya tesota) from the Arizona-Sonora Desert Museum.


  1. Sean

    How many years after germination, does it take a young Ironwood tree to start producing its’ own seeds.

  2. Roberta


    Ironwood trees are extremely slow growing, which is why their wood is so dense. In my experience it might be around 15 years or even longer.

  3. Sean

    Thank you for responding. You are certain that it takes 15 years for it to produce seeds on its’ own?

  4. Roberta

    We have a tree that is at least 15 years old and it is yet to flower, let alone produce seeds. Ironwood trees do not necessarily flower every year, even when mature. You can read more about them here:

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.