Desert Senna: Wildflower for Wildlife

Desert senna is an excellent wildflower for attracting and supporting bees, butterflies, hummingbirds, and other pollinators. It’s carefree and blooms much of the year with virtually no maintenance. Here’s how to grow and care for this southwest desert native.

Desert senna (Senna covesii) is a shrubby perennial with small, leathery green-gray leaves reminiscent of those of pea plants. Ruffled, lemon-yellow flowers bloom intermittently from spring through fall. Flowers are followed by thin brown seed pods that split open to release their seeds.

This wildflower is native to the Mojave and Sonoran Deserts. You’ll see it growing in sandy washes and along roadsides, sidewalks, and just about anywhere the soil is poor or disturbed.

Desert senna is easy to grow. These plants are tough. They can easily handle the desert’s heat, sun, and aridity, and require almost no maintenance.

They need little water. In their natural habitat, they can survive on as little as 3” of annual rainfall.

Desert senna is a boon to wildlife. The flowers attract hummingbirds, bees, and butterflies, while the seeds provide food for birds and mammals. Additionally, it serves as a larval host for many species of moths and butterflies.

Why I Like This Plant

• Cheerful yellow flowers
• No thorns, non-toxic, low-litter
• Thrives on neglect
• Important plant for wildlife

Things to Watch Out For

Desert senna reseeds freely, so you may find seedlings popping up where you didn’t plant them. This may be a drawback or a feature, depending on your situation. (I eagerly look forward to volunteers in my garden!)

Optimal Growing Conditions

If you’re thinking of adding desert senna to your garden, you need to find a suitable place that will keep your plants looking good and coming back every year.

Here are the key factors to keep in mind.

Temperature

Desert senna can take whatever heat is thrown at them. Some transportation departments use them as a roadside wildflower to populate barren land and help prevent erosion.

They can survive temperatures down to 25℉ and should ideally be grown in USDA Hardiness Zones 9 – 11.

Sun Exposure

Desert senna grows best in full sun, and I mean real death-star Arizona sun. These are tough desert survivors that can handle unrelenting sun and reflected heat.

Size and Growth Rate

Desert senna grows moderately fast and typically reaches a size of 2 feet tall by 1 to 2 feet wide.

Soil

Desert senna prefers sandy soil, but will grow in rocky or clay soil provided it’s well-draining. In their native habitat, these plants can be found growing in disturbed areas, rocky slopes, or sandy river washes.

Desert Senna:
The Essentials

Common Name	Desert senna
Scientific Name	Senna covesii
Origin	Mojave, Sonoran Deserts
Plant Type	Perennial
USDA Zones	Zones 9 – 11
Cold Hardiness	To 25℉
Flower Color	Yellow
Flower Season	Spring, summer, fall
Mature Size	2′ high x 1-2′ wide
Growth Rate	Moderately fast
Sun Tolerance	Full, reflected sun
Water Needs	Low
Pests & Diseases	None
Garden Friendly	No thorns, low litter, non-toxic
Wildlife	Supports birds, bees, butterflies

Growing Desert Senna: Seed & Transplants

Desert senna is not commonly sold at most nurseries, but you may find it at a nursery that specializes in native plants.

If you can’t find plants locally, you can easily grow them from seeds. You can order seeds online from Phoenix Desert Seeds or Native Seeds/SEARCH.

You can gather seeds, provided you do so responsibly. Please see A Guide to Collecting and Growing Sonoran Desert Wildflowers. This brochure, published by the Native Arizona Plant Society, will tell you everything you need to know about collecting wildflower seeds.

While this plant is plentiful in Arizona, it’s considered “rare or endangered” in California, so please refrain from gathering seeds there.

Do not dig up wild plants!
They rarely survive and you will have deprived
the area of next year’s seedlings.

When to Plant

If you’re starting with transplants, plant them as soon as you buy them. Disturb the roots as little as possible — wildflowers do not like being transplanted.

Since desert senna is considered a warm season or “monsoon wildflower”, the best time to sow seeds is in late spring, shortly before the monsoon rains begin.

Recommended Reading:
The Easy Way to Grow Desert Wildflowers

How to Care for Desert Senna

Desert senna doesn’t require much care. In fact, care guidelines are more about what not to do.

There is no need to fertilize desert senna, which evolved to grow in desert soil. And since it is a member of the legume family (Fabaceae), its roots fix nitrogen, which naturally improves the surrounding soil.

They should not be on irrigation. Rainwater should provide your seeds and plants with most of the water they need. While they can survive on rainwater alone, they’ll look better with some supplemental water. If you experience a prolonged dry spell, hand water every few weeks.

Pruning is not necessary, but you can remove any dead or cold-damaged branches in late winter or early spring.

Plant Lover Facts

Desert senna (Senna covesii) goes by a large number of other names, most commonly coves’ cassia. But it is also called Coues’ cassia, Coues’ senna, cove senna, rattlebox, rattlebox senna, rattleweed, and dais.

‘Cassia’ refers to its previous scientific name, Cassia covesii. ‘Coues’ refers to Elliot Coues, an American ornithologist.

It is native to Arizona, Nevada, New Mexico, California, and northern Mexico.

Did you enjoy this article?
Sign up for our weekly newsletter
where you’ll find more great info on creating &
maintaining a beautiful, carefree desert landscape.

Photo Credits

Chris English, CC BY-SA 3.0, Wikimedia Commons

Krzysztof Ziarnek, CC BY-SA 4.0, Wikimedia Commons

Krzysztof Ziarnek, CC BY-SA 4.0, Wikimedia Commons