Western Mugwort

With the common name of mugwort and a summertime floral display that can only be described as underwhelming, Artemisia douglasiana is on no published lists of the top perennials for a knockout spring or summer garden. Mugwort is humble and unassuming, yet handsome in its own distinctive way and a workhorse in revegetation projects, especially where subjected to both drought and seasonal flooding.

Artemisia douglasiana, western mugwort

Mention mugwort and most people, if they know the name at all, will respond with an opinion about its medicinal uses or the allergies caused by its wind-blown pollen. Usually they are thinking of another mugwort, Artemisia vulgaris, a highly variable plant native to Eurasia and found throughout much of the northern hemisphere. Western mugwort, A. douglasiana, is native to western North America from the southwestern tip of British Columbia to the northern Baja California peninsula.

Depending on who’s counting, there are more than 300 to 500 species of Artemisia, at least a dozen of which are commonly known as mugwort. Mugworts and many other artemisias, commonly known as sagebrush or wormwood, have been in use for centuries for medicinal, spiritual, and culinary purposes. A. douglasiana is no exception.

 Common mugwort (Artemisia vulgaris), known in medieval times as the “mother” of herbs, has been shown by modern research to have antioxidant, anti-inflammatory, analgesic, antibacterial, and many other medicinal qualities. Japanese mugwort (A. princeps) is native to China, Japan, and Korea, where leaves and young seedlings are still used in preparing many different foods. Annual mugwort (A. annua) is an important component of traditional Chinese medicine and a source today of drugs for the treatment of some types of malaria. A. douglasiana, our focus here, has long been used by native American tribes for medicinal and ceremonial purposes.

Some parts of some artemisias can be highly toxic in some applications so caution is always advised in considering their use as food or medicine. Caution should also be advised for their use in gardens. These are, for the most part, good-looking plants with stunning foliage, adapted to full sun and little to no summer water. They are especially useful in gardens in summer-dry climates.

Artemisia suksdorfii, coastal mugwort

However, many artemisias spread by rhizomes and some spread rather fast. Of these some are more easily controlled than others. Artemisia vulgaris is considered an invasive weed in some parts of the world and can be virtually impossible to fully contain.

Artemisia douglasiana may suddenly extend its reach with sufficient winter rains, but with restricted summer water it does not usually overwhelm other plants. A. suksdorfii, also native to western North America but mostly closer to the coast, spreads by rhizomes to form small colonies. Unless I prove to be wrong in the long run (always possible with natural spreaders), it seems to travel less and to be more easily removed than other rhizomatous artemisias. A. suksdorfii and A. douglasiana may hybridize where their ranges overlap.

In my experience, Artemisia douglasiana is not so aggressive as to be considered invasive where it is naturally found. In 1978 I planted three one-gallon plants of another rhizomatous spreader, Matilija poppy (Romneya coulteri), on a steep, surficially slipping bank below my house in northern California. Some years later, when the poppies had already spread widely and were doing their job, a few plants of A. douglasiana appeared on their own and these have also spread, gradually inserting themselves among the poppies. This fortuitous combination has secured the bank and, at least so far, the two plants have co-existed amicably. Neither seems to impede the other and together they are holding the bank.

Artemisia douglasiana in the Santa Barbara Botanic Garden

Something else about Artemisia douglasiana that cannot go without comment: Like those of most others in the genus, the leaves of A. douglasiana have a strong and uniquely pleasing fragrance that makes working among them a special treat and causes deer to routinely avoid them.

If you have the space to accommodate their spread, and you don’t mind the fact that they are dormant in winter, welcoming western mugwort into your garden can be surprisingly rewarding. Cut it the ground in late summer or fall and wait for the emergence of new, lusciously soft, gray-green leaves in the earliest weeks of spring.