The Native Artemisias

There are several native artemisias that are naturally well-adapted to our soils and climate, drought-tolerant, and useful in our landscapes. These silver-leafed shrubs make great contrasts with green foliage and great foils for flowers of any color. They are now classified under three genuses: Seriphidium, Oligosporas and Artemisia.

         Big Sage, now Seriphidium tridentatum (formerly Artemisia tridentata) is a western native of semi-arid and alkaline conditions, generally preferring 7”-15” inches of annual rainfall. It is often found in gullies and ravines where water flows part of the year. Where soils are deeper with more water, this woody shrub can get 6’-12’ tall, but in poorer conditions it may only get 3’ high or less. It has a vigorous root system both tap rooted and shallow rooted to take advantage of water wherever it is available. Because it is so adaptable and is not very palatable to animals and because it produces copious seeds, it is possibly the most abundant shrub in North America.

         The silvery leaves of Big Sage are quite variable both in size and shape, usually having three-toothed ends (tri dentata), although some are not lobed. Like other artemisias, it has hairs covering the leaf surface which help reduce water loss. Like the ancient Roman dictum says, Even a hair casts a shadow. Other drought-tolerant mechanisms of Big Sage are: dropping of spring leaves which are too big and soft, reducing photosynthesis in summer, maintaining high concentrations of salts and other soluble materials such as sugars which create a resistance to water loss.

         It flowers in August with clusters of tiny flowers on upright stems. These depend on wind for pollination and so are not very attractive to insects or to people, although Big Sage is the state flower of Nevada. The pollen, like that of other artemisias, is very irritating and hay fever inducing. Two subspecies are identified: Seriphidium trid. wyomingensis, growing in the driest conditions and Seriph. trid. vaseyana, growing at higher elevations in moister conditions.

         Big Sage grows well in our area. I have one in sandy gravel with no supplemental water that has become 5’ high and 6’ wide in eight years. It is often considered a sloppy shrub, however Betsy Baldwin, a specialist in native plants, gave me a hint as to how to correct this. Of course it has a wild appearance, which can be very attractive, but what happens often is that snows break down the branches and leaves the shrub disheveled. By training it to a single trunk and by removing weak branches with narrow crotches, especially in the primary structure along the main trunk, the shrub doesn’t break as easily. Also shortening branches to keep the shrub more compact reduces breakage.

         The other native Seriphidium is S. canum (aka Artemisia cana). This sage is shorter, up to 5’, more silvery and more water-requiring than Big Sage. Of course, its great pungent and refreshing aroma is one of the main reasons to have one around.

         Two native artemisias now classified by taxonimist William Weber as Oligosporas are Sand Sage and Common Sagewort. Sand Sage, Oligosporas filifolia (commonly known as Artemisia filifolia) is a lovely, silvery-plumed variety that gets to 4’ high. It grows very dry and in the landscape is best cut back by a third after flowering. It is very ornamental, especially when planted with tall penstemons. Another Oligosporas that volunteered in my prairie neighborhood is Common Sandwort, O. campestris (Artemisia campestris). It has a greener coloration and long arching stems to 3’. Although not showy, some people really like it in my garden. It is reported to be a biennial, but I cut mine to the ground every year after flowering and it has been perennial for over ten years.

         There are a number of native artemisias that Weber and others still classify as Artemisia. Artemisia frigida, Silver Sage, is an abundant volunteer on my property. It grows 4”-14” high and has attractive silvery, fringed leaves. It looks its best where I have removed the competition of bigger weeds and have kept it mowed high. If allowed to elongate and flower, it can look ratty after blooming, and then self-seed copiously. This is fine too in our wilder areas, where a dense silver “lawn” might be just right.

         Artemisia ludoviciana is another volunteer on my property. Selected forms are sold as Silver King or Silver Queen, but even the species has very white leaves, especially on the underside. It makes a wonderful silver background or great filler with cut flowers, but gallops aggressively through the garden and is difficult to remove. I keep mine on the dry edge of a wall. The nice selection ‘Valerie Finnis’ is fine in my xeriscape, having a showy spring, then collapsing in the summer heat and returning in the fall. However it may be too invasive for many gardeners.

         There are so many other artemisias: the herbs like mugwort, tarragon and wormwood; the cultivated varieties like A. stelleriana ‘Silver Brocade’, A. ‘Powis Castle’, A. canescens (A. versicolor), A. lactiflora, A. ‘Tiny Green” etc. But these are other stories.