Russian Sage (Perovskia atriplicifolia or Salvia yangii) is a popular, drought-tolerant perennial valued for its silvery foliage and late-season lavender-blue flowers. Although gardeners often describe this plant as aggressive due to its vigorous spreading habit, it is generally not classified as an ecologically invasive species in most regions of the United States. Its tendency to expand rapidly within a cultivated flower bed is a function of its natural growth mechanisms, which can be managed with proper gardening techniques.
Distinguishing Aggressive Growth from Invasive Status
The terms aggressive and invasive describe two distinct types of plant behavior. A plant is considered aggressive when it spreads rapidly and vigorously within a managed garden space, often outcompeting nearby cultivated plants for resources like water and nutrients. This growth is typically limited to the boundaries of the garden or landscape.
In contrast, an invasive species is defined as a non-native plant whose introduction causes or is likely to cause environmental or economic harm. Official invasive status is often regulated at the state or federal level and involves the plant escaping cultivation to colonize wild areas. Russian Sage rarely meets the criteria for this ecological classification because it does not typically displace native flora in undisturbed habitats.
How Russian Sage Spreads
The reputation Russian Sage has for being aggressive stems from its two main biological mechanisms for lateral expansion. The first is through rhizomatous growth, which involves underground stems or runners that radiate outward from the parent plant. These rhizomes send up new shoots, resulting in the plant forming a steadily widening clump.
This perennial also possesses a strong tendency toward prolific self-seeding, especially when planted in ideal, well-drained conditions. The numerous seeds produced by the long-lasting flower spikes are highly viable and can disperse easily, leading to many volunteer seedlings popping up throughout the garden the following season. These two factors, the subterranean runners and the dispersed seeds, combine to give the plant its vigorous, space-consuming nature.
Managing Garden Expansion
Gardeners who wish to enjoy Russian Sage without its aggressive characteristics taking over their beds can employ a few targeted management strategies. To control the spread of underground rhizomes, consider installing a physical barrier around the planting area, such as a root barrier sunk into the soil. Planting the sage in a large container or pot sunk into the ground also creates an effective underground containment system.
Managing the plant’s tendency to self-seed involves deadheading. Removing the spent lavender flower spikes immediately after the blooms fade prevents the formation of viable seeds that would otherwise drop into the soil. This must be done before the seed heads fully mature and dry out, typically in late summer, which significantly reduces the appearance of volunteer seedlings.
Finally, a hard pruning in early spring, cutting the plant back to six to twelve inches, encourages strong, upright growth and helps maintain a tidy, controlled shape.