Types of Ironwood Tree (Olneya) ID Chart, Growing Zones & Surprising Trick

Georgette Kilgore headshot, wearing 8 Billion Trees shirt with forest in the background.Written by Georgette Kilgore

Forestry, Trees and Tree Planting | January 9, 2024

Image of an Ironwood Tree in an oval frame with desert sands around it with distinctive Olneya ironwood tree leaves, branches and roots.

The Ironwood Tree still amazes onlookers and continues to surprise gardeners around the world with it’s awesome properties.

Did you know that unlike other woods…it doesn’t float!

If you have the desire to update your landscaping design or secure your desert property, the Olneya or notably known as Olneya tesota, is a perfect addition.

The Olneya tesota enriches the surrounding shrubs and live for centuries. But there is some confusion on what are the true benefits of this keystone species.

Although there are 80 types of Ironwood Trees that are admired for their strength and durability, each Ironwood Tree has its own unique characteristics.

This powerful canopy tree can provide more than just shade for your backyard, and this complete guide explains everything you need to know about planting and maintaining an Ironwood tree, its benefits and how to identify them.

Desert Ironwood Identification Characteristics

It can get confusing when talking about the Ironwood Tree characteristics. Ironwood Trees are extremely dense and cannot float like Pine Trees or Cedar Trees.

Here are a few things you should know about the Desert Ironwood Tree (Olneya):

Ironwood Tree

(Olneya tesota)

Ironwood Tree in oval frame on green background.
  • Characteristics: The tallest tree in the Sonora desert. It provides shade and does not frost. The Olneya tesota is extremely resistant to heat.
  • Family: Part of the pea family. Some call the Desert Ironwood a relative of the Fabaceae family.
  • Genus: Olneya
  • Leaf: Oval green leaf-spine
  • Bark: A thin thorny gray-brown bark.
  • Seed: A brown and black seed.
  • Blossoms: When the leaves fall for the spring. Flowers bloom to a purple or pink color.
  • Fruit: Edible brown and black pea pods
  • Native Habitat: Arizona (Sonora Desert), California, and Mexico
  • Height: Can grow up to 50 ft.
  • Canopy: Yes. Protects plants and wildlife from extreme heat and frost.
  • Type: Deciduous, however, the Ironwood Tree sheds just enough leaves to preserve energy and water for the upcoming flowers. The Desert ironwood does not shed all its leaves.

Although the Sonoran Desert Ironwood is not deemed endangered, it is a protected species in Arizona and Mexico. The Olneya tesota have been protected by the State of Arizona since the 1970s.

Ironwood Tree Facts: How To Identify Ironwood Tree

Here is the list of factors that can be used on how to identify Ironwood Tree:

Ironwood Tree Flower

Desert Ironwood Trees bloom in the spring in what often resembles pea blossoms. They are expected in April and last for up to 18 days.

Desert Ironwood Tree identification chart showing full-grown Desert Ironwood tree with average height, Desert Ironwood Tree leaf, Desert Ironwood Tree flower, Desert Ironwood Tree fruit, and Desert Ironwood Tree bark images in circle frames on a green background.

The purple or pink flowers grow in the middle of the stem. These flowers are approximately 2.5 centimeters in size.

Ironwood Tree Leaves

For these types of Ironwood Tree (Olneya), especially in this specie, the leaves are essential. The leaves of the Desert Ironwood Tree are significant and do not fall all at once.

This Desert Ironwood Tree is never without leaves. The leaves grow in pairs and have pair spines.

Ironwood Tree Seeds

The brown or black seeds are edible. Their pods can actually be planted to grow more Ironwood Trees.

For many Southwestern residents, the thought of waiting for several years to enjoy a mature tree is not ideal.

The evolution of the Olneya tesota is a very slow-growing process. The Desert Ironwood Tree grows approximately 12 inches a year during germination.

Surprising Trick: Ironwood Sinks or Float

The welcoming surprising trick for the Ironwood is it does not float. The unique types of Ironwood (Olneya), or Olneya tesota are the densest wood in its pea family.

Although not the hardest wood in the world like the Australian Buloke, the Olneya tesota is certainly the hardest in the Southwestern area of the United States.

The hardness of the Olneya tesota is determined by the Janka Test. The density, according to the Janka Wood Hardness Scale, is about the resistance of the wood.

The Janka Wood Hardness Scale measures the density of wood, meaning it determines how difficult it is to make a dent in the wood.

Wikipedia The Free Encyclopedia reports determining whether an Ironwood sinks or floats is whether the wood is denser than water.1

Contemplating whether the wood can sink or float is about the proportion between the weight and volume. The weight and volume ratio provides the information needed to determine the density of the wood.

If a log wood can float down a stream, it is less dense than water. However, if the wood log is a mighty Ironwood Tree, it will sink due to being more dense than water.

Identification Chart: What Kind of Trees Are Considered Ironwood Trees?

The most drought-resistant tree in the Sonoran Desert is the Ironwood Tree. However, not every Ironwood Tree is created equal.

Each Ironwood may have some similarities in its wood density.

However, depending on the area, the Ironwood Tree may have different needs and benefits according to its ecosystem. The plants listed below are some of the Ironwood Trees located in several parts of the United States:

  • American Hornbeam Ironwood Tree
  • Black Ironwood Tree
  • Persian Ironwood Tree
  • Mountain Ironwood Tree
  • Brazilian Ironwood Tree

American Hornbeam Ironwood Tree

The American Hornbeam Ironwood Tree is also referred to as Musclewood. The scientific name is Carpinus caroliniana from the family of the Betulaceae (Beech).

This Ironwood Tree is nestled in the lower areas of Vermont, North Dakota, North Carolina, and other parts of the Eastern and Midwest areas of the United States.

Wide shot of American Hornbeam Ironwood Tree showing orange flowers blooming.

(Image: Department of Horticulture11)

With seeds starting as green seeds that become tan, squirrels and other animals appreciate the American Hornbeam seeds and fruit.

The American Hornbeam needs moisture; however, the soil can drain adequately to ensure housing its dense wood. As often seen next to riverbanks and streams, this Ironwood Tree does well in areas with more moisture than other Ironwood families.

The flowers and leaves of the American Hornbean are sensitive to extensive heat and do well in shaded areas. The flowers are yellowish-green.

The leaves are orange or red in the falls and turn to an attractive dark green in the spring and summer.

Black Ironwood Tree

Young Black Ironwood Trees with mulch on the ground, situated in a garden.

(Image: Department of Horticulture12)

From Africa, Mexico, Honduras, the Caribbean, and Southern Florida, this Blackberry Tree has one of the densest wood, almost comparable to the Olneya tesota Sonora Desert Ironwood Tree.

This plant is from the Rhamnaceae family. The species Black Ironwood Tree is from the genus Krugiodendron.

With the yellowish-green flower that blooms throughout the year with an almond aroma. However, the flower blooms in the spring and summer.

Black Ironwood is also called Leadwood because of the aroma of lead it gives when cut. Grown in the environment of a Hammock with other plants.

The Hammock may include trees such as the Oak Tree. The blackberries that grow from its dark green leaves are edible for humans and birds.

Persian Ironwood Tree

From the Ruby Vase Persian Ironwood Tree to the Weeping Persian Ironwood Tree, the habitat is similar to the Sonoran Desert. It can survive in sandy soil and in a dry climate.

This tree is native to Northern Iran but made its way to the United States.

Unlike the Olneya Ironwood Tree, Persian Ironwood Trees are found in Central California, Seattle, North Carolina mountains, and throughout the United States.

Persian Ironwood Tree situated in a park showing long branches and hues of orange and yellow leaves.

(Image: AnRo000213)

The Persian Ironwood Tree is in the Hamamelidaceae family. There are two species, the genus Parrotia in the United States and P. Subaequalis, which are grown in China.

With a distinctive peeling of silver, pink-like brown color, and cream bark, that is described as a mosaic with various colors, the leaves are famous for their fall colors of orange, yellow, red, and purple. In the summer, the leaves are dark green.

Before the foliage, the flowers appear in winter to early spring. These flowers are described as Parrotia flowers.

The flowers are dark red or pink stamens. The seeds are double capsules with one seed in each.

Mountain Ironwood Tree

Closeup of Mountain Ironwood Tree showing gray-barked branches and dark-green leaves.

(Image: Department of Horticulture14)

The Mountain Ironwood Tree is found in Arizona, California, Mexico, Northwestern New Mexico, and Oregon. The bees and butterflies enjoy habituating in the Mountain Ironwood.

The Mountain Ironwood is in the Rosaceae family and genus Cercocarpus. The spring flowers are white and clustered.

Often called the Mountain Mahogany. Although not an authentic Mahogany Wood, like each dense wood, this Ironwood is tolerant to dry climates.

The Mountain Ironwood helps its environment to prosper with its seeds and shading feather leaves.

The Mountain Ironwood is also a companion plant for its plant and tree neighbors. As a nitrogen-fixing plant, it helps increase the nutrients in the soil for its surrounding habitat.

Brazilian Ironwood Tree

The Brazilian Ironwood Tree is not only in Brazil, Bolivia, and Singapore, it can be found in the United States. Because of its similar look to Rosewood, some may call it Bolivian Rosewood.

The Brazilian Ironwood is in widespread use to make guitars and basses. But it can be found in certain parts of California, Louisiana, Texas, and Florida.

Wide shot of Brazilian Ironwood Tree situated next to a road showing dense and rich foliage.

(Image: John Robert McPherson15)

The Sonoran Desert Ironwood Tree and the Brazilian Ironwood Tree are in the same legume group, the Fabaceae family. This plant genus is Libidibia.

The leaves are feathery and oval. With flowers growing in bunches, it’s a stunning yellow that began as a seed pod.

The bark of the Brazilian Ironwood Tree has a nickname of the “Leopard Tree.” The bark has similar spots to the leopard.

These trees mentioned above do well in drought climates compared to other trees.

Trees such as the Magnolia Tree care need a lot of watering, especially their first two years of growth.

Unlike Magnolia Tree, Ironwood Tree can survive and flourish with less water intake. Magnolia Tree requires more maintenance compared to the Ironwood Tree family.

Each tree above has a common trait; they each are shading Ironwood Trees. Not all sturdy trees are Ironwood Trees, such as the Basswood Tree, Hazelnut Tree, and Chocolate Mimosa Tree.

However, the Chocolate Mimosa Tree is in the same family as the Fabaceae or Legume family, like the types of Ironwood Tree (Olneya).

Types of Ironwood Tree (Olneya) and Its Ecosystem

Often referred to as a nursing plant because of its impressive ability to shade the Sonoran Desert, such as bobcats and birds, these types of Ironwood Tree (Olneya) are also a desert wildlife source for food and shelter.

The plant seeds from the Ironwood Tree provide nutrition to birds, small reptiles, various birds, and other large animals such as coyotes. These brown seeds are high in protein.

How dense the wood is for the ironwood species is repeatedly reported in studies and preferred by wood artisans. The thorny wood from the Ironwood Tree can weigh up to 66 pounds, according to the University of Arizona.2

But the ecosystem of the Sonora Desert relies on the Ironwood Tree, including the cactus that nestles under the Olneya tesota for its survival.

Approximately 500 different animals and desert plants rely on the shelter and nutrients of the Ironwood Tree, according to the Arizona-Sonora Desert Museum.3

The genus Olneya tesota protects wildlife species and desert plants from extreme heat. The ecological need for this Sonoran Desert Ironwood Tree helps cool the habitat with shade.

However, during those chilly nights, the nursing plant prevents the freezing of its habitants.

This up-to-50-foot Ironwood Tree houses several birds that nest with their new baby chicks and various mammals that give birth to their new young under the canopy.

Ironwood Tree Growing Zone

Growing zones for Ironwood Tree where to grow is repeatedly asked for green thumb enthusiasts. However, each Ironwood Tree growing zone depends on the types of Ironwood Trees and the proper soil to germinate properly.

According to Arizona State University, the Sonora Desert Ironwood Tree growing zone is 9-11.4 These hardiness zones are especially rich in the best dry weather with rich soil.

The best growing conditions for Ironwood Tree vary in each zone. The Sonora Desert is located in the southern part of Arizona and in the southeastern parts of California.

The Arizona region is in Zone 10b and California 11a. The Olneya tesota Ironwood Tree lives in these areas.

The Olneya tesota Ironwood Tree does not cause harm to the environment like an invasive tree. Blackcoyote Medicine reports the Desert Ironwood can live 1,500 years.5

As beautiful as many of the different Ironwood species are, the Sonoran Desert Ironwood Tree may not do as well on the Island of Hawaii.

Although some may wonder if the Ironwood Tree Hawaii invasive to the island. Like many USDA Hardiness Zones on the mainland, Hawaii is proud of the She-Oak Ironwood Tree.

The She-Oak plant is appreciated due to its slow growth and is maintained by The City and County of Honolulu.

The She-Oak is famous for aligning the King Carriage Road at the Kapi’olani Regional Park. This family of Ironwoods belongs to the Casuarinaceae family.

The USDA Hardiness Zones are 9a and 13a.

Whether an Ironwood Tree or not, each plant grows healthy in the right growing zone to ensure it thrives. Not too many plants, such as the Black Locust Tree, can grow prosperous in several climates and temperatures.

According to U.S. Forest Service, the Black Locust Tree is found throughout the U.S. and can be grown on virtually any soil type.6

The Black Locust Tree is also in the same pea family as the Olneya Ironwood Tree, the Fabaceae family.

Ironwood Tree Growth Rate

The slower the growth of the tree, the harder and dense the wood will be.

Although Ironwood Tree growth rate may vary, the primary growth rate is extremely slow.

Ironwood Tree growth chart showing full grown Ironwood Tree on a line graph with Ironwood Tree age on the x-axis and Ironwood Tree height on the y-axis.

The slow growth can decrease to a snail’s pace during a drought. This pace is exactly what you want.

These types of Ironwood Tree (Olneya) grow slowly by design.

In the proper habitat, the Desert Ironwood Tree can grow at its proper growth rate of 1 to 2 feet a year as a minimum growth rate in a well-maintained garden.

Some Ironwood Trees grow slightly faster, such as the Ostrya virginiana. The University of Kentucky Department of Horticulture reports that Ostrya virginiana grows up to 10 to 15 feet within a 15-year time.7

Certain Ironwoods, such as the Persian Ironwood Tree, have a medium growth rate. Although 10 to 15 feet in a 10-year time span is a normal tree growth rate.

A medium growth rate is 1 to 2 feet per year. However, slow growth is under 1 foot a year.

How To Grow an Ironwood Tree

The Sonoran Desert Ironwood Tree or the Olneya tesota is a keystone species and is needed for the desert ecosystem.

The idea of growing an Ironwood Tree of this type is encouraged.

Desert Ironwood tree situated in a desert showing few leaves growing on branches.

(Image: Photo by Brad Sutton, NPS16)

The Olneya tesota cannot thrive in a soil with high salt content. Certain areas, such as Southeastern Florida, would not be ideal for this type of Ironwood Tree.

However, dry and desert temperatures are the best climate to grow a healthy Ironwood Tree.

To accomplish germination within a week, you must decide if you will do the following:

  • Scarification Ironwood Seeds
  • Seeding an Ironwood Seed
  • 15-gallon container Ironwood plant

Some don’t believe the scarification of Desert Ironwood seeds is necessary, and others prefer seeding. The below will give you more of a better idea of how you want to grow your Olneya tesota.

Scarification Ironwood Seeds

Scarification is the process of soaking a seed prior to planting and a great way to growing Ironwood Tree from a seed. Soaking your Olneya tesota seed will provide ample moisture to signal its germination process.

Because the natural soil made for this type of Ironwood Tree is drier than most, scarification or soaking your Ironwood Tree seeds may be a great idea.

Pre-planting treatment by soaking your Desert Ironwood seed is often up for debate. But if you believe your soil may need some help, soak the seed in water for 12 to 24 hours.

Seeding an Ironwood Seed

Growing an Ironwood Tree from a seedling is a great option. A Desert Ironwood seeding has already begun its plant-growing process.

Seeding is often a small tree plant that must have the correct depth of a hole to be planted.

15-Gallon Container Ironwood Plant

Supporting your local nursery by purchasing a 15-gallon container Ironwood plant puts you ahead of the germination. The other benefit is your Ironwood Tree will be approximately 6-12 inches tall.

This 15-gallon Ironwood Tree is about six months to one year old. As required by the seeding method, placing the container in the proper deep depth will prevent drying out the roots or the plant not getting enough oxygen.

It is recommended by Iowa State University that when planting your tree in a container, allow the root ball to be your guide.8 Digging a hole 2-3 times wider than the diameter of the root ball is a rule for most green thumb gardeners.

5 Planting Tips for Ironwood Tree

Planting your Ironwood Tree requires more planning and adequate preparation.

Although the Ironwood Tree is known for its dense wood due to its very slow growth to maturity, it’s also low maintenance.

Wide shot of Desert Ironwood tree situated in a desert showing wide foliage span with the blue sky in the background.

(Image: Bob Wick17)

To make sure your Desert Sonoran Ironwood Tree is planted properly, consider the 5 planting tips for Ironwood Tree below:

  1. Seeds should be planted ¼ deep in well-drained soil.
  2. Place the Ironwood seed or 15-gallon in a location it can grow large.
  3. Planting a seed is best in May-July.
  4. Plant the 15-gallon Ironwood Tree in October for better-continued growth.
  5. Watering needs for Ironwood Tree plants, in the beginning, are frequent.

After your Ironwood Tree is over a year old, watering is once a month. Because this is a desert tree.

During the first year, the more you water, the more tree trunks will grow. Be sure to plant the tree where it can grow up to 30 feet wide.

Planting your Ironwood Tree in full sunlight with very little shade is what your tree needs. It can withstand temperatures no colder than 20 Fahrenheit.

The Ironwood Trees germination process is best in 60-70 degree weather.

Types of Ironwood Tree (Olneya): Pruning and Winter Care

When the Desert Ironwood Tree is young, pruning often is needed. Removing water sprouts from the young tree branches is necessary.

Low and crowded branches should also be removed.

Taking vegetative shrubs away from your young Ironwood Tree will help the nutrients keep the tree healthy. As the tree gets older, pruning should be required less and less.

Incorporating manure or fertilization also helps the growth of the Ironwood Tree.

Be sure to consult with your local nursery about how much fertilizer or if it’s needed for your Ironwood Tree. Some believe the use of manure or fertilizer may increase the risk of root rot or possible pest issues while the tree is young.

Growing an Ironwood Tree from a cutting is unnecessary for this Desert Tree. Ironwood Trees in various genus are known to need very little maintenance as it matures.

The Best Use of a Desert Ironwood Tree

The Desert Ironwood Tree and other species of Ironwood Trees are primarily used for tools and artifacts.

However, many Southwestern residents enjoy Ironwood Trees for their beauty and security.

Ironwood Tree situated in front of a building showing wide canopy with dark green leaves.

(Image: Department of Horticulture18)

Incorporating Desert Ironwood in your landscaping design is ideal for rock gardens and a grove of security trees. But ultimately, less irrigation is the primary benefit of Desert Ironwood Trees.

Besides using Ironwood Trees as an aesthetic for low-maintenance landscaping, the Ironwood Tree is also used for firewood, fence posts, and wood carvings.

Ironwood Tree Disease Prevention: Common Pests of the Ironwood Tree

Olneya tesota has had to withstand droughts and sometimes unusual weather trends for over 1,000 years. The non-biodegradable wood or wood trunks are protected from rooting and often common tree diseases because of the toxic chemicals it carries.

Among the toxins that are infectious to humans is Silica. However, without Silica and other toxic chemicals, the Ironwood Trees would be susceptible to disease.

A healthy Desert Ironwood Tree is often resistant to disease and pests. If you’re located in the best place that is suitable for planting an Ironwood Tree, as noted in the Hardiness zone 9-11, ideally, your sandy soil may be perfect for the Olneya tesota.

The right soil is crucial in preventing disease and pests from invading the trunks and foliage of your Ironwood Tree. The foliage or the leafy canopy can be the entrance point for common pests and fungi such as:

  • Texas Root Rot
  • Aphids

The Texas Root Rot and Aphids can wreak havoc on your Ironwood Tree. However, it is preventable.

Here is a better overview of how these pest attack Desert Ironwood Trees:

Texas Root Rot

The Texas Root Rot is a fungus,10 also known as Cotton (Texas) Root Rot, that the Sonoran Desert Ironwood Tree has been infected. The Texas Root Rot infects trees and plants in lower desert areas.

The Olneya tesota grows in the lower desert below 2,500 feet. This fungus thrives in warm weather and wilts the leaves, and kills the tree much faster than an Ironwood grows.

How to stop Ironwood Tree disease like the Texas Root Rot is unfortunately unstoppable. The white Fungus in the sandy soil cannot be cleansed with fertilizers or chemicals.

Although the Desert Ironwood Tree is semi-evergreen, the fungus may appear with light brown web lines on the surface of leaves, which cannot be stopped. It is not an immune plant to Cotton (Texas) Root Rot.

The only solution, according to the University of Arizona report published by the United States Department of Agriculture, is to remove the tree and re-plant it if the Ironwood Tree is viable.9

Aphids

Aphids are an insect that happens to be a vampire when it comes to a leaf’s sap.

The Aphids suck the sap from leaves, especially from ornamental trees such as the Olneya tesota.

Yellowish-green Aphids infesting a leaf.

(Image: Scot Nelson19)

Tulip Trees and Weeping Willows are known to drip sap, not Ironwood Trees. Ironwood Trees are deciduous trees that do not drip sap which is known as honeydew.

This honeydew is due to a possible infestation of Aphids.

Leaving behind a sticky residue and attempting to spread viruses and diseases can be prevented. It’s not ideal to see yellowish leaves and damage to the aesthetics of your tree, but there are natural pest controls for your garden and landscaping.

The best natural pest control for Ironwood Tree in your backyard oasis are ladybugs, Mummified Aphids, and lacewings. Carnivorous insects such as ladybugs and lacewings help the Desert Ironwood Tree live a long, healthy life without disease.

Small parasitic wasps lay eggs into the Aphids and later hatch as a larva that eats the inside of the Aphids. The Aphids become mummified after their death.

These mummified Aphids can no longer do any damage to the tree.

In contrast, the Purple Leaf Plum tree is often plagued by diseases such as root rot and leaf curl, to name a few.

The Desert Ironwood Tree has historically been unaffected by debilitating diseases and remains one of the best canopy trees for desert areas, so if you’re interested in adding one to your garden, it can last for centuries.

Frequently Asked Questions About Ironwood Tree

What Are the Best Months on When To Plant Ironwood Tree for the Best Yield?

It’s recommended to plant an Ironwood seed directly in the soil from early April to June. To plant in the ground with a 15-gallon, mid-summer to October is the best time for planting.

What Are Some of the Companion Plants for Growing Ironwood Tree?

Ironwood Trees are nitrogen-fixing trees. The Sonoran Desert Tree will enrich the soil and roots of companion plants such as Cacti, Mesquite Tree, Brittlebush, and more.

What Distance Should Be Considered on How Far Apart To Plant Ironwood Tree?

Desert Ironwood Trees grow their canopy of leaves up to 30 feet wide. Ideally, trees are planted 50 to 60 feet apart to allow ample space for the trunk’s growth.

How Much Sunlight Does Ironwood Tree Need Each Day?

It is recommended that the Olneya tesota Ironwood Tree get a minimum of six hours of direct sunlight.

How Often Do a Young Olneya Tesota Ironwood Tree Need To Be Watered?

It’s recommended to water your Sonoran Desert Tree deeply. Watering deeply may require an hour or two several times a week to ensure the roots grow down to the soil strong.

How Can I Avoid Sunburn to the Sonoran Desert Ironwood Tree?

Pruning your Ironwood Tree in the cooler months, such as Winter, is recommended to avoid sunburn.

Is the Olneya Tesota an Evergreen Ironwood Tree?

The Olneya tesota is a semi-evergreen tree. This means the Ironwood Tree is part deciduous and only sheds some of its leaves to preserve water.

Can I Eat the Seeds From the Olneya Tesota?

The young green bean taken directly from the pod in early summer can be eaten without roasting. The mature beans can be roasted after soaking for various recipes.

Besides Olneya Tesota, Is There Another Common Name?

Yes. These types of Ironwood Tree (Olneya) are also called Palo Fierro.

Read More About Ironwood Tree

References

1Wikipedia. (2022, September 1). Olneya. Wikipedia. Retrieved May 7, 2023, from <https://en.wikipedia.org/wiki/Olneya>

2Rymer, C. (2003, July 28). The Ironwood: Stately Sanctuary in the Sonoran Desert. Cooperative Extension Maricopa County Journal. Retrieved May 7, 2023, from <https://cals.arizona.edu/maricopa/garden/html/pubs/0803/ironwood.html>

3Hubbard, T. (2023). Biological Survey of Ironwood Forest National Monument. Arizona-Sonora Desert Museum. Retrieved May 7, 2023, from <https://www.desertmuseum.org/programs/ifnm_ironwoodtree.php>

4Martin, C. (2023). Olneya tesota. Virtual Library of Phoenix Landscape Plants. Retrieved May 7, 2023, from <https://www.public.asu.edu/~camartin/plants/Plant%20html%20files/olneyatesota.html>

5Blackcoy. (2022, February 1). Ironwood. Blackcoyote Medicine. Retrieved May 7, 2023, from <https://blackcoyotemedicine.org/2022/02/01/ironwood/>

6Taylor, D. (2023). Black Locust (Robinia pseudoacacia). USDA | U.S. FOREST SERVICE. Retrieved May 7, 2023, from <https://www.fs.usda.gov/wildflowers/plant-of-the-week/Robinia-pseudoacacia.shtml>

7University of Kentucky. (2023, May 3). American Hophornbeam. University of Kentucky | College of Agriculture, Food and Environment. Retrieved May 7, 2023, from <https://www.uky.edu/hort/American-Hophornbeam>

8Iowa State University. (2023). How Large of a Hole Should Be Dug When Planting a Tree? Iowa State University Extension and Outreach. Retrieved May 7, 2023, from <https://hortnews.extension.iastate.edu/faq/how-large-hole-should-be-dug-when-planting-tree>

9Olsen, M. W. (2009, May). Cotton (Texas) Root Rot. USDA | NRCS Field Office Technical Guide. Retrieved May 7, 2023, from <https://efotg.sc.egov.usda.gov/references/public/AZ/Texas_Root_Rot.pdf>

10UNIVERSITY OF CALIFORNIA AGRICULTURE AND NATURAL RESOURCES. (2017, March). Phymatotrichopsis Root Rot (Texas Root Rot). UC | IPM. Retrieved May 7, 2023, from <https://ipm.ucanr.edu/agriculture/alfalfa/phymatotrichopsis-root-rot-texas-root-rot/>

11Breen, P. Oregon State University. Retrieved from <https://landscapeplants.oregonstate.edu/plants/carpinus-caroliniana>

12Krugiodendron ferreum Photo by Daderot / CC0 1.0 Universal (CC0 1.0) Public Domain Dedication . Resized and Changed Format. From Wikimedia Commons <https://commons.wikimedia.org/wiki/File:Krugiodendron_ferreum_-_McKee_Botanical_Garden_-_Vero_Beach,_Florida_-_DSC03107.jpg>

13Persischer Eisenholzbaum Photo by AnRo0002 / CC0 1.0 Universal (CC0 1.0) Public Domain Dedication . Resized and Changed Format. From Wikimedia Common <https://commons.wikimedia.org/wiki/File:20141119Parrotia_persica1.jpg>

14Cercocarpus betuloides Photo by Dinkum / CC0 1.0 Universal (CC0 1.0) Public Domain Dedication . Resized and Changed Format. From Wikimedia Common <https://commons.wikimedia.org/wiki/File:Cercocarpus_betuloides.JPG>

15Libidibia ferrea Photo by John Robert McPherson / Attribution-ShareAlike 4.0 International (CC BY-SA 4.0). Resized and Changed Format. From Wikimedia Common <https://commons.wikimedia.org/wiki/File:Libidibia_ferrea_Sunbury_St_Geebung_P1100865.jpg>

16Desert ironwood tree NPS Photo by Brad Sutton / Public Domain Mark 1.0. Resized and Changed Format. From Flickr <https://flic.kr/p/M28Npy>

17Ironwood Forest National Monument Photo by Bob Wick / Public Domain Mark 1.0. Resized and Changed Format. From Flick <https://flic.kr/p/GCTgx1>

18Breen, P. Oregon State University. Retrieved from <https://landscapeplants.oregonstate.edu/plants/olneya-tesota>

19Aphids, feeding on a leaf Photo by Scot Nelson / CC0 1.0 Universal (CC0 1.0) Public Domain Dedication . Resized and Changed Format. From Flickr <https://flic.kr/p/C4cmCd>