The genus Artemisia contains about 300 species of plants, so there's a good deal of variety, including evergreen and deciduous shrubs, perennials and annuals. It is in the Asteraceae, or daisy, family, but you won't see a lot of showy flowers. Most artemisia plants are grown for their filagree-like leaves. Some you might be familiar with are southernwood, wormwood, Sweet Annie, Absinth, mugwort, sagebrush and the culinary herb tarragon.
Artemisia is often considered an herb, either culinary or medicinal. Most of the species are heavily scented and many have a somewhat bitter taste, which makes them very unattractive to browsing animals, but useful for their essential oils.
A vignette of all silvery and white plants looks striking in semi-shade, for instance, artemisia, lamb's ear, pulmonaria, and white variegated grass. Gray leaves also pair nicely with just about any pastel, especially pinks and blues, as well as with mauve-pinks, like Joe Pye Weed and Centranthus ruber.
A beautiful use for artemisias is to pair with the spiky, deep blues and purples of salvias and iris. Or watch what it does to liven purple coneflowers. Small plants are great for containers. Taller and bushier varieties can be used as a summer hedge.
Leaves: Alternate, in various shapes. Very often the leaves are lobed and they are generally covered with whitish hairs that give the leaves a silvery, gray look.
Flowers: Small (1/16 to 3/8 inches), white or yellow, cylindrical flowers, often in panicles, but sometimes single.
Artemisia ludoviciana (USDA Hardiness Zones 4 through 8) with multiple subvarieties including:
- 'Latiloba': Compact, and less aggressive than most, with heavily lobed leaves. They grow up to two feet wide and three feet high.
- 'Silver King': probably the most widely available. Attractive and nice for arrangements, but it can be very aggressive. 'Silver Queen' is similar, with more finely cut foliage. They grow up to five feet high and four feet wide.
- 'Valerie finnis' (western mugwort, white sage): a North American native, it tends to spread quickly, but it has attractive, coarsely toothed leaves. Washes out in hot sun. They grow up to three feet high and three feet wide.
- Artemisia 'Powis Castle': Very delicate-looking, deeply cut, gray leaves. Can become woody and looks best if cut back by ½ to 2/3s, before new growth starts in the spring. USDA Hardiness Zones 6 through 8; they grow up to three feet high and three feet wide.
- Artemisia schmidtiana 'Nana': A dwarf cultivar, also known as Silver Mound, forms tight clumps of lacy, silver foliage. They can become woody, without pruning, and can look somewhat ratty in the center in hot, humid summers. USDA Hardiness Zones 3 through 8; they grow up to one foot high and one foot wide.
- Artemisia stelleriana 'Silver Brocade': Deeply cut, almost oak-like leaves and very tolerant of poor conditions. They grow up to 12 inches in height and 30 inches wide.
Artemisia is relatively low maintenance, but it does have some preferences when it comes to their environment.
Soil: Artemisia are not particular about soil pH and they do not like overly rich soil. As with most silver-gray leaved perennials, they are very drought tolerant. They will need regular water, until the plants are established, but can take care of themselves after that. With a few exceptions, like Artemisia lactiflora, artemisias need well-draining soil. If left sitting it damp soil, they will decline and/or be short-lived.
Planting: Plants can be started from seed, divisions or cuttings. Many of the newer hybrids are sterile and the others won't grow true to seed.
Exposure: They will grow best in a full sun location, although most varieties can handle partial shade.
Since artemisia do not like rich soil, no supplemental fertilizer should be necessary, if you are regularly adding organic matter to your beds.
Perennial artemisias can be cut back in the fall or spring. Shrubby varieties should be pruned in the spring. They can handle being cut back hard if you want to keep their size in check.
Even non-woody artemisia can get floppy, especially after flowering. Give them a shearing mid-summer, to prevent them from splitting open in the middle.
Divide plants every two to three years, or when you start to notice the center beginning to die out.
Pests and Problems
Luckily, if the conditions are ideal, artemisia is quite a resilient plant. There are, however, a few things to watch out for when it comes to their health:
Diseases: Artemisia can be prone to many fungal and rusts diseases, like white rust, powdery mildew and downy mildew. Hot, humid weather exacerbates these problems. Growing them in an open area with good airflow will help mitigate the problems.
Pests: Because of their strong scent, insects tend to avoid artemisias.