by Dr. Jacqueline A. Soule
If you grew up in Arizona in the 1960s you learned that the state is renowned for “The Five C’s:” Climate, Cattle, Copper, Citrus, and Cotton. Since then, several million people have moved into the entire Southwestern region for the first C – the climate, and now the once-extensive fields, groves, and cattle ranches are mostly just a part of our history.
I like history, and am glad that there is a native cotton species we can use in our landscapes to celebrate our unique land. I am referring to Gossypium thurberi, also known as Arizona wild cotton, Thurber’s cotton, desert cotton, and in Spanish as algodoncillo or little cotton.
While cultivated cotton is treated as an annual, it is technically a perennial shrub, and so is desert cotton, forming a vase-shaped shrub to small tree that reaches 10 to 15 feet tall.
The leaves are palmately lobed and medium textured. Leaves vary in size with the amount of water the plant receives. Leaves on wild plants are generally two to three inches across, but in the landscape they can be five inches across and form a dense screening shrub with a flat emerald-green hue.
Don’t plant this as a screen though, because all those lovely leaves turn even lovelier shades of red, maroon and almost purple in autumn. Due to this deciduous nature, it is best planted as a background shrub.
At a former home, I pruned a desert cotton up into a single-trunked tree, and it never failed to have a parade of visitors in autumn, some exclaiming over my ability to grow “Japanese maple.” For anyone that desires autumn color, it is an excellent choice.
Gossypium thurberi is in the Malvaceae, the mallow family, but unlike many members of the family, individual flowers are not showy. Flowers are similar to the desert mallow in size and architecture, but colors tend to be creamy white to yellow with a hint of pink to bright crimson spots on the petals. En mass, the blooms can be quite striking, and I enjoy their mild fragrance.
The flowers develop into small dark brown pods called bolls. These are less than an inch around and fairly fragile, breaking apart and blowing away. This could be an issue in yards with pools, but are not a problem in a natural landscape. The leaf litter in autumn is confined to a three-week window. Despite my desire for more of these lovely plants, they did not reseed extensively around the yard, a plus for most homeowners.
When it comes to planting desert cotton, consider that it is usually found growing on rocky slopes, in canyons and along road sides. It is found from the Superstition Mountains of Arizona, and south and east into Mexico and Texas. Although in the wild it is generally found in well-drained soils, my “tree” did very well in clay soil with infrequent water.
As for cold hardiness, the desert cotton is dormant in winter and survived the killer freeze of 2011, the same one that killed my “ten-degree tangerine.” Although plants are not found in the wild in Nevada or northern New Mexico, this may be due to rainfall rather than temperatures.
As for wildlife, desert cotton does not appear to be browsed by rabbits or javalina. It is a larval food plant for the Arizona royal moth (Citheronia splendens sinaloensis) and appears to be pollinated by the solitary desert bees.
Back in the 1930s attempts were made to erradicate this plant from the mountains and foothills of southern Arizona. It was believed that the weevil found feeding within the bolls was the infamous cotton boll weevil. Taxonomic studies by Dr. F. Werner determined that the Thurber weevil was not the same as the cotton weevil and that it did not affect cultivated cotton. Luckily the eradication efforts failed and the plant has returned to be a fairly common, attractive native plant.
Currently there are a few local, specialty nurseries currently sell desert cotton, generally in one or five gallon sizes. It can also be found on-line with named cultivars. This charming desert native certainly deserves a second look for xeriscape use across the Southwest.
Dr. Jacqueline A. Soule is an award winning garden writer and author of 10 books, eight of them on landscape plants and gardening in the Southwest. She currently lives, teaches and writes in Tucson, AZ, where she also serves as chair of the Advisory Board of the Desert Legume Program. More about her online at Gardening With Soule.com.