The answer to whether Artemisia schmidtiana ‘Silver Mound’ is a perennial plant is yes, it is generally grown as an herbaceous perennial. This popular cultivar, often simply called Silver Mound, is valued in the garden for its fine-textured, silvery-gray foliage that forms a dense, cloud-like cushion. Its mounding growth habit and distinctive color make it an excellent choice for contrast, edging, or rock gardens. The plant is primarily grown for this attractive appearance rather than its inconspicuous summer flowers.
Understanding the Perennial Life Cycle
A perennial plant lives for more than two years, contrasting with annuals and biennials. Herbaceous perennials, such as Silver Mound, die back completely to the ground each winter. While the above-ground growth withers, the root system remains alive underground in a state of dormancy. This root system stores energy reserves to survive freezing temperatures. When the soil warms in the spring, the perennial breaks dormancy and sends up new shoots from the crown, allowing it to return reliably year after year.
Hardiness and Regional Growing Zones
The successful overwintering of Silver Mound depends heavily on the USDA Plant Hardiness Zone Map. This plant reliably thrives as a perennial across USDA Zones 3 through 8. Within this range, the root crown is insulated enough to withstand minimum winter temperatures and return vigorously in the spring.
However, its perennial status is nuanced at the edges of this range. In extremely cold climates, such as Zone 2, severe winter temperatures may kill the dormant root crown, forcing gardeners to treat it as an annual. Conversely, the plant struggles in regions with excessive heat and high humidity, even if the winter is mild.
The combination of heat and moisture can lead to stem or root rot, causing the plant to prematurely die back. Silver Mound’s dense foliage, which helps it tolerate drought, becomes a liability in humid conditions by trapping moisture against the crown. Therefore, its longevity requires a balance of cold tolerance and freedom from persistent moisture.
Essential Maintenance for Longevity
Ensuring Silver Mound returns year after year requires specific maintenance focused on promoting dense, healthy growth. One important practice is the “spring haircut,” or severe pruning, performed in early spring before significant new growth begins. Cutting the plant back by up to two-thirds prevents leggy growth and helps maintain its signature tight, mounding shape.
Pruning is also necessary in mid-summer if the mound begins to split or “splay” open, which can happen if the soil is too rich or the plant is overwatered. Shearing the plant by about one-third encourages a flush of new, dense foliage and prevents the center from dying out. Proper soil and light are paramount to overwintering success.
Silver Mound requires full sun and very well-drained soil; it prefers sandy or poor ground. Rich soil or excessive fertilizer encourages weak, floppy growth prone to splitting and root rot, compromising its ability to survive the next winter. To maintain vigor, mature clumps should be divided every three to five years, removing the older, woody center portions and replanting the healthier perimeter sections.