Is seep willow part of the willow family? How can I tell a seep willow plant from a willow tree?
Today’s flora feature explores these commonly asked questions. We’ll break down the differences between seep willows and willow trees (hint: they may look similar, but they are not closely related) and provides some identification tips so you can keep an eye out for these water-loving Sky Island plants when hiking, camping, or participating as a volunteer in our Spring Seeker program.
P.S. Be sure to read all the way to the end for a bonus willow surprise!
While the name is deceiving, seep willow (Baccharis salicifolia) is actually a member of the sunflower family Asteraceae. Seep willow is a tall, narrow shrub with long, widely serrated, pointed leaves. From March to December, it forms clusters of fuzzy white flowers toward the tips of its stems, which attract pollinators including native bees and butterflies. When the flowers go to seed, they turn puffy—a sight resembling a mature dandelion flower.
Seep willow is native to the Southwest U.S. but can also be found throughout Mexico. It is sometimes used for medicinal purposes. Alternative names for seep willow include mule-fat and water wally. Seep willow’s specific name in Latin, Baccharis salicifolia, means “willow-leaved.”
Fun fact: Seep willow is cousin to desert broom, a common desert plant in the same genus.
The willow family (Salicaceae) is a large one. Under this family we have the genus Salix. There are approximately 129 willow species detected in North America, and according to Southwest Desert Flora, we can find 20 of these Salix species in the Sky Island region, including . Unfortunately, not all of them are native to the southwest. (For example, weeping willows are native to China.)
Different willow species grow as shrubs or trees. In Arizona, willows generally have long rigid or loosely hanging branches covered in thin, finely serrated leaves. Between March and June (depending on the species), willows will grow fuzzy yellow or white along the stems. Some species bear small fruits in the summer months after flowering.
Fun fact: Our local cottonwood trees (Populus) are also a part of the willow family Salicaceae.
The seep willow plant grows at elevations up to 5,500 feet. It prefers riparian areas or wetlands where there is a consistent water source, so it is most likely found near springs, year-round streams, or shallow groundwater areas .
Willow species grow at elevations up to 9,500 feet. Nearly all willow species prefer riparian areas with streams, creeks, and seeps—so they’ll often be found in ecosystems also inhabited by seep willow.
In the Sky Island region, seep willow and willow species are both listed as stable. However, in certain states, willow species are listed as threatened and endangered due to degraded habitats.
Seep willow and willow species are most often found near seeps, springs, or other water sources. Here are some traits to look for when hiking, camping, or volunteering for our Spring Seeker program:
- Woody plant, shrub
- Musky, incense-like scent, stronger when flowering
- Grows between 3 and 10 feet tall (usually ~7’)
- Green, widely serrated leaves
- Leaves between 3 and 6 inches long, slightly sticky
- Green or tan stems (often tan or lighter brown than willows)
- Fuzzy round white flowers, clustered, tinged pink or red
- Fluffy bristles once flowers mature (imagine the seeds of a dandelion)
- Flowers nearly year round
- Woody plant, tree or shrub
- Tree growth between 40 to 65 feet tall
- Green, finely serrated leaves, or smooth-edged
- Leaves between 2 and 5 inches long, can alternate sizes
- Grey bark with deep fissures/cracks
- Long yellow catkins, sometimes dotted pink or red
- Flowers between March and Jun
Bonus: Desert Willow
You know what else isn’t a true willow? Our desert willow (Chilopsis linearis).
Desert willows are willows in name only. They can be found in drier areas than both seep willows or real willows. Desert willows are trees and produce beautiful large pink flowers in the summer that attract all sorts of pollinators. In non-blooming seasons, long, slim, empty seedpods hang from desert willow branches. Wildlife often eat these seeds as part of their diet.
AZUTM Tree Guide Southwest Desert
SEINet – Baccharis Salicifolia
Southwest Desert Flora – Seep Willow