There is something about the leaves of the Wild Senna that beckon to be touched. Perhaps it’s because they look very much like the leaves of the Sensitive Plant (Mimosa pudica) – both in the Fabaceae family – that respond to touch by closing its leaves. Whether you touch it or not, Wild Senna’s tropical vibe is delightful for several reasons. With its adaptability to many conditions and soils, its beauty, and wildlife benefits, Wild Senna is a must in any landscape. Underutilized Wisconsin native perennial in most residential gardens, Wild Senna is an attention-grabbing perennial with distinctive, delicate leaves and uniquely shaped bright yellow flowers that bloom in mid-July.
You may also know this plant as American Senna or Indiana Senna.
While flowers are somewhat short-lived and diminutive, they will stop you in your tracks with their unusual appearance. Bonus: Wild Senna flowers provide substantial nourishment to butterflies, solitary bees, and bumble bees!
In fall, leaves turn a brilliant golden yellow, and in winter dark brown seed pods add color and texture to the garden.
If you need more reasons to plant Wild Senna, it’s considered threatened or endangered in many parts of the Northeastern United States. In Wisconsin, it’s plant of Special Concern or categorized as a Species of Concern. Be a conservationist in your own yard and plant Wild Senna!
Wild Senna does well in part to full sun and while they are naturally found in areas with clay and moist conditions, they can tolerate dry areas, and once established can withstand occasional drought.
Growing upwards of 6-feet tall and 3-feet wide, Wild Senna is shrub-like in appearance making it a great backdrop for shorter perennials, along woodland edges, or as a hedge. They are excellent additions to pollinator and native gardens providing height and structure, and as abundant food for many species. With their ability to withstand high winds and a deep taproot, they are excellent for use on slopes.
Adding to the uniqueness of Wild Senna, its flowers do not have nectaries to attract pollinators like that of other flowering plants. Even so, its pollen attracts bees in droves, particularly Bumble and Sweat Bees. According to a 2016 study conducted by Penn State, Picky eaters: Bumble bees prefer plants with nutrient-rich pollen, it was found that Wild Senna is a favorite of Bumble Bees with high protein-to-lipid ratio pollen. When visiting, bees use buzz pollination to shake, rattle and roll the pollen onto their lower abdomen and legs. It’s a delightful sound and one that you need to experience! With declining bee populations worldwide, planting more Wild Senna is a great way to help our apian friends. Note: in addition to Wild Senna, other plants in this study ranked highly with our bee friends including Spiderwort and Culver’s Root – perennials native to Wisconsin!
For an added layer of protection, Wild Senna has secondary nectar sources that are separate from the flowers. Strategically positioned on the leaf stems near the primary plant stem and next to the flower buds, ants, parasitic wasps, and lady beetles are rewarded with nectar for protecting the plant against leaf-eating predators. Smart AND sneaky!
Wild Sennas are a host plant for a variety of butterflies including the Orange-barred Sulphur (Phoebis philea), one of the largest Sulphurs in Wisconsin, and the Silver-Spotted Skipper (Epargyreus clarus). The Gorgone Checkerspot (Chlosyne gorgone), a Wisconsin Special Concern species, is attracted to the pollen of the Wild Senna.
A rare migrant to Wisconsin, the Cloudless Sulphur butterfly prefers Wild Senna as it is one of their host plants. Larvae will eat both the leaves and flowers. The caterpillar will turn green when eating the leaves or pale yellow if eating the flowers.
Once flowering is complete, clusters of flat and long brown seeds resembling pea pods appear, providing food for game birds such as the Northern Bobwhite (Colinus virginianus), a quail of Special Concern in Wisconsin, as well as wild turkeys, and songbirds.
An easy-to-grow perennial that adapts to a variety of conditions, Wild Senna needs minimal care. It tends to reseed and sprawl, making it an excellent choice in naturalized or restoration settings. If planted in a contained area, seed pods can be removed in late summer or early fall before they split open in winter and disperse.
In-Season Foliage & Fall Foliage
Black Walnut Tolerant: Yes
Deer Resistant: Yes
Rabbit Resistant: Yes
Wild Senna has no serious insects or disease problems unless you consider caterpillar damage by the aforementioned sulphurs and skippers to be problematic. Most mammals, including deer and rabbits, don’t dare sample Wild Senna as it contains a compound called anthraquinones, which causes severe stomach and bowel upset.
The genus Senna, is from the Arabic ‘sana’, meaning “brightness and radiance.” The species epithet hebecarpa is from two Greek words, ‘hebe’, for “youth”, or “dawn of puberty” and ‘carpos’ for “fruit”, referring to the fuzzy seed pods.
According to Nicholas Culpeper’s book, English Physician and Complete Herbal, penned in 1789, the leaves of Wild Senna were used as a laxative as well as to clear away obstructions in the body, blood, and lungs.
Other sources indicate that the Cherokee used the root of the plant to treat high fevers, fainting spells, and pneumonia. The Iroquois used a compound as a tapeworm remedy and the Meskwaki ate the seeds to soothe sore throats. Infusions of the plant were also used for cramps, heart trouble, and poultices for sores. The Kiowa ground and boiled the seeds to make a coffee-like beverage.
With its carefree habit, the options for companion plants are limitless. For a riot of colors and textures plant alongside Red Milkweed, Pale Purple Coneflower, Wild Bergamot, Ironweed, Rattlesnake Master, Prairie Blazing Star, Sky Blue Aster, as well as ornamental grasses such as Prairie Dropseed or Little Bluestem.
If a monochromatic look is desired, pair Wild Senna with other yellow flowers such as Stiff Coreopsis, Cup Plant, Compass Plant, Moonshine Yarrow, or any number of Black-eyed Susan varieties. The combinations are endless – go wild!