Desert Ironwood (English)
Compiled by Jill Lorenzini
Family: Fabaceae or Leguminosae (Pea family)
Latin name: Olneya tesota
Tohono O’odham Name: ????
Spanish Names: palo de fierro, palo de hierro, tésota, comitín, una de gato
Desert Ironwoods are one of the oldest and most intriguing trees of the Sonoran Desert. Named for their dark, dense wood, they can be recognized by their grey bark, small dark-green leaves, small thorns, and lovely pink blooms. The tree is now a protected species in Arizona. It grows at elevations below 2500 feet, often in xeri-riparian areas. It is prized among desert harvesters for its edible flowers and seeds.
Keystone Species and Beautiful Shade Tree
One of the Sonoran Desert’s most important trees, Desert Ironwood is named for the dark, dense wood it produces, long valued for its durability, decay-resistance, beauty, and strength.
Desert Ironwood is a “keystone” species of the Sonoran Desert: a tree with enormous ecological value, critical to the very structure and function of the desert. It is considered a “habitat modifier,” as it plays a primary role in creating the ecosystem it occupies, and greatly enhances desert diversity. It does this by creating shade, building soil, and providing shelter.
Although these trees shed some leaves and branches in response to drought and temperature extremes, like so many desert-adapted plants (e.g., palo verde, ocotillo, limberbush), mature Desert Ironwood trees are mostly evergreen. The bluish-green foliage is dark and dense in wet years and seasons, sparser and grayish-green in dry ones. Precious shade zones are created under their thick canopies, offering a microclimate up to 15 degrees F cooler than surrounding unshaded areas. Seedlings and plants vulnerable to desiccation from heat and aridity find sanctuary here and, subsequently, increased chances of survival.
When a Desert Ironwood sheds it leaves, branches, bark, seedpods, and flowers (as well as birds’ nests and droppings from the many species that nest or roost in Ironwoods), these materials decompose, and an enriched soil zone is formed underneath its canopy. Branches of older trees often droop down and touch the ground, enclosing and sheltering this area. Organic matter and nitrogen, amendments often in short supply in desert soils, are added to the soil year after year.
These islands of fertility provide germination and growth opportunities for many important desert plants, such as saguaro cactus and night-blooming cereus. In turn, these oases offer shelter, shade, and food to desert creatures, from insects to mammals. Also, as is typical of legumes, Desert Ironwood roots form nitrogen-fixing nodules, making this essential nutrient available to plants in its root zone. In deserts, plant growth is limited by nitrogen supply. Plants growing under or near Desert Ironwood trees gain distinct advantages due to this proximity.
Because of its significant role as a keystone species, nurse plant, and habitat modifier, Desert Ironwood has been a protected species since the 1970s in Arizona, and since 1993 in Mexico. Ironwood Forest National Monument was created in Tucson, Arizona, in 2000 to preserve habitat and teach desert dwellers about the many benefits of this special plant.
Desert ironwoods are great trees for the home landscape—mostly evergreen, they provide shade, cooling, and habitat for native birds. Plant a 5-gallon Desert Ironwood next to a water-harvesting basin and, once established (after two to three years), it will need no supplemental water.
HARVEST: Like those of other leguminous desert trees, ironwood flowers and seeds are edible. Ironwoods generally flower from late April through May and set seed pods a few weeks after. The light-beige pods will dry in June-July. Both fresh and dry pods can be harvested.
Fresh green seeds are found inside light-beige pods. Seeds should be sweet and slightly peanutty tasting. If so, gently pull whole pods off the tree and put them in your harvesting container. If they taste chalky you’ve waited too long to harvest them fresh. Let them continue to ripen on the tree and harvest when pods are fuzzy, dry, and dark brown!
Dry seeds are hard and brown and found inside dry pods, which are fuzzy and brown and easy to harvest. Rather than picking by hand, you can put a tarp on the ground and gently shake free the dry pods. But do not harvest dry pods/seeds off the bare ground.
PROCESS & STORE: Whether fresh or dry, ironwood seeds should be cleaned and processed for storage as soon as possible after picking to preserve freshness and reduce the chances of the pods moldering.
FRESH PODS/SEEDS should be blanched the day you pick them to prevent ripening or moldering. They can be blanched in the pod or shelled like peas and then blanched. To do this, wash your pods or seeds in cool water. Bring a pot of water to a boil. Meanwhile, prepare a large bowl of ice water. Add whole beige pods or just the green seeds to boiling water and boil for at least 90 seconds. Remove, drain and immediately place in ice water for 90 seconds. Once cooled, drain and package in labeled and dated plastic freezer bags, getting out as much air as possible.
DRY BROWN PODS/SEEDS are also best processed the day you pick, but can also be stored in an unsealed container outside until you do. Do not store in a plastic bag or they will molder! To process dry seeds, free them from the pod by hand or by laying them on a clean tarp, covering them with a clean sheet, and walking on it to crush the dry pods. Winnow out the pod, leaving just the dry dark brown seed. Freeze seeds for two days to prevent bruchid-beetle infestation. Store in the freezer until use or take them out, dry thoroughly and then store in a sealed jar.
EAT: Desert Ironwood flowers can be eaten raw in salads or candied for use in desserts.
Although the seeds can be eaten raw, both green and dry/brown stages of seeds may be most easily digested when blanched, sprouted or cooked.
After blanching beige pods, salt and eat the green ironwood seeds from the shell like edamame. Or use them in salads or soups, as garnish, or sauté or roast with seasoning.
Dry seeds are best eaten simply sprouted, or sprouted and then parched/roasted. To sprout: soak overnight and then rinse daily until seed coat splits open and sprout emerges. Remove sprouts by squeezing the split seed coat. Rinse with clean water and then use sprouts raw or lightly cooked. To parch/roast: Sprout seeds just until the tiny root emerges (1-2 days). Dry seeds in the sun, solar oven, or conventional oven set to 150 F. Once dry, put seeds in a dry skillet over medium heat to cook until seeds pop. Season with salt or other spices.
Click to download the information from the section above as a PDF file: Desert Ironwood
(credits correction: URL for Bean Tree Farm is www.BeanTreeFarm.com)
Workshop Description: The Desert Ironwood workshop has been designed to be used in situations both with and without electricity and access to a computer. It is a hands-on workshop that teaches the basics of how to identify, harvest, and process Desert Ironwood seeds. It is recommended to be given in a situation where you can first discuss the information and then go out when pods/seeds are ripe and actually harvest, giving participants hands-on experience with tasting and picking good pods. The season for this is usually late spring/early summer for green seeds and June for dry seeds – although this varies with elevation and yearly rainfall. However, if actual harvesting is not possible, the workshop can be given indoors or outdoors without the harvesting component.
The workshop begins with discussion about the importance of planting native trees in urban areas and using water-harvesting techniques to maintain these trees around one’s home and neighborhood. Participants then engage in activities to learn how to identify Desert Ironwood trees, as well as learning about this keystone species’ important role in the Sonoran Desert. Participants then learn how they can harvest and process their seeds at home, and how to preserve seeds for long-term storage. Suggestions are also given for good ways to incorporate Desert Ironwood seeds into their meals.
This Workshop Kit Contains:
- Labeled jars with dry samples of Desert Ironwood seeds and pods.
- A flash drive with:
- PowerPoint presentation with photos of basics of rainwater harvesting, Desert Ironwood trees, plant parts for identification, processing and storage options,
- Desert Ironwood video,
- Workshop outline in Microsoft Word, and
- Instructions for gathering plant samples to bring to the workshop.
- Laminated color photos of all slides in the PowerPoint presentation.
- Desert Ironwood Pocket Guides for handouts.
- A copy of Eat Mesquite! A Cookbook, for display.
Other Desert Foods Workshops
Desert Harvesters offers workshops on harvesting, processing, and cooking with a variety of desert foods: Mesquite, Prickly Pear Fruit and Pads, Desert Ironwood, and Palo Verde. If you prefer a generalist approach, or need a workshop that is indoors and doesn’t include harvesting, we also offer a 2-hour Desert Foods Overview which combines the individual plant kits and offers a simple introduction to these plants and foods rather than in-depth explorations into each. Contact us for more information.
Need a Workshop Instructor? Hire a Desert Harvester!
Experienced harvesters are available to teach a workshop for your organization, business, or school. Please contact us for information on availability and fees.
Funds for this project were provided by the Urban and Community Forestry Financial Assistance Program administered through the State of Arizona Forestry Division – Urban and Community Forestry and the USDA Forest Service.