Artemisia schmidtiana ‘Silver Mound’ is a perennial cherished for its soft, finely dissected, silvery-gray foliage. This cultivar forms a dense, cushion-like mound, making it a popular choice for garden edging, rock gardens, and providing textural contrast in landscape design. Its delicate, lacy leaves offer a striking visual element throughout the growing season, acting as a neutral spacer that complements flowering plants with cooler colors like pinks and blues.
Defining the Growth Habit
The core question of whether Artemisia schmidtiana ‘Silver Mound’ spreads can be definitively answered: it is a clump-forming perennial, not an aggressive spreader. Unlike some relatives in the Artemisia genus, this particular cultivar is not invasive and does not send out runners or aggressive underground rhizomes. Its growth is primarily outward from a woody central crown, resulting in a slow, predictable expansion of its diameter.
This naturally contained habit means it remains well-behaved in garden beds and does not require containment barriers. The plant achieves a relatively modest mature size, typically reaching a height of 6 to 12 inches. The width, or spread, usually ranges from 12 to 18 inches, though some mature specimens can reach 24 inches in diameter. This full size is often reached relatively quickly within the first few months of the spring growing season.
Managing Mature Size and Shape
While ‘Silver Mound’ is not aggressively spreading below ground, its above-ground growth often requires intervention to maintain its tidy, hemispherical shape. The primary management concern is the tendency for the plant to “flop” or split open in the center during the mid-summer heat. This splaying is often a result of rapid vegetative growth, which causes the stems to become too heavy for the plant’s structure to support.
To counteract this, gardeners employ a preventative pruning technique known as the “Chelsea Chop” in the late spring. This process involves cutting back the entire plant by about one-third to one-half of its current height. This is typically done around late May or early June, coinciding with the first major flush of growth. This timely shearing stimulates dormant buds lower on the stems, leading to denser, more compact new growth.
The resulting bushier habit is significantly less likely to collapse under its own weight later in the season. Furthermore, this pruning removes the small, yellow, and horticulturally insignificant flower buds that appear in mid-summer. Removing these buds redirects the plant’s energy away from reproduction and back into producing the characteristic, fine, silvery foliage, thus maximizing its ornamental appeal.
If the plant has already flopped in the summer, a hard cutback of several inches can be performed to encourage a new, tighter flush of growth. This mid-season trim is done to reset the appearance, though it is less effective than the preventative spring chop. The resulting foliage will also be less dense than a plant that received the earlier maintenance.
Environmental Factors Affecting Plant Health
Maintaining the signature dense, silvery cushion depends heavily on providing the correct environmental conditions, as stress often leads to the same splaying issues that pruning addresses. The most common cause of failure is excessive moisture, which can cause the plant to rot or “melt out” from the center. This perennial requires full sun exposure, meaning it needs at least six hours of direct light daily to maintain its silvery color and dense form.
It is adapted to thrive in poor, lean, and very well-drained soils, often tolerating sandy or rocky conditions. Planting in rich, fertile ground or over-fertilizing encourages weak, excessive vertical growth that inevitably leads to the plant flopping open. Gardeners should avoid adding nitrogen-rich fertilizers, which promote soft, leggy growth that easily collapses.
Once established, the root system is quite drought tolerant. Watering should be infrequent, allowing the soil to dry out considerably between applications, sometimes up to three inches deep. High humidity combined with excessive moisture is particularly detrimental, making the foliage prone to rot and further exacerbating the collapse of the central crown.
Ensuring good air circulation and avoiding overhead watering helps mitigate the risk of fungal issues in humid climates and allows the delicate foliage to dry quickly. Proper site selection is paramount to the plant’s long-term health and ability to hold its tight, mounded shape.