Russian Sage (Perovskia atriplicifolia, now often classified as Salvia yangii) is a hardy, fragrant perennial valued for its silvery foliage and lavender-blue flower spikes. This drought-tolerant plant is a popular choice for gardens and xeriscaping, thriving in difficult, dry conditions. Its ability to withstand heat and poor soil is directly linked to the specialized structure of its root system. Understanding how deep and wide these roots grow is key to successfully managing this vigorous plant.
Structure of the Root System
The Russian Sage develops a dual-purpose root structure composed of two primary components. Over several seasons, the plant establishes a deep, woody taproot that anchors the shrub and penetrates far into the subsoil. This deep structure is responsible for the plant’s exceptional drought tolerance, allowing it to seek out moisture long after surface water has evaporated.
Complementing this taproot is a network of finer, fibrous roots closer to the soil surface that absorb nutrients and water during periods of regular moisture. The development of this extensive system is encouraged by watering new transplants deeply and infrequently during their first year. Once established, this tough, woody root mass makes mature Russian Sage plants difficult to successfully relocate or transplant.
How Russian Sage Spreads
The lateral spread of Russian Sage is facilitated by underground stems known as rhizomes. These rhizomes grow horizontally beneath the soil surface, acting as runners that extend outward from the main plant crown. As they grow, they periodically send up new shoots, sometimes called suckers or offsets, which emerge as new plants several inches away from the parent clump.
This rhizomatous growth pattern allows the plant to naturalize, which can be seen as aggressive in a contained garden space. While the plant is not formally classified as invasive, its tendency to expand its footprint is a concern for gardeners. To manage this lateral spread, establish a physical boundary, such as a buried root barrier, around the planting area. Alternatively, simply dig up and remove the unwanted new shoots and runners as they appear to maintain the desired clump size.
Root Division and Propagation
Gardeners can utilize the plant’s root system to create new plants through division or cuttings. Dividing the root ball is the most reliable method for propagation and is often performed every four to six years to rejuvenate an aging or oversized clump. The best time for this process is typically in the early spring as new growth emerges or in the late fall after the plant has finished flowering.
To divide, the entire plant is carefully dug up, and the woody root ball is sectioned using a sharp spade or knife. Each resulting division must contain a healthy portion of established roots and several stems to ensure successful re-establishment. An alternative method is to take softwood stem cuttings in the summer, dipping the cut end in a rooting hormone to encourage new root growth.
Planting Depth and Soil Requirements
When planting Russian Sage from nursery stock or divisions, proper depth is important for root health. The plant crown, where the stems meet the roots, should be set level with the surrounding soil surface. Planting the crown too deeply can lead to crown rot, a common cause of plant failure, especially in cooler, wetter climates.
The root system requires specific soil conditions to thrive and prevent disease. Excellent drainage is paramount, as the roots are susceptible to rot in heavy, waterlogged soil. Russian Sage performs best in lean, rocky, or sandy soil with a slightly alkaline pH, mimicking its native arid habitat. When planting multiple specimens, spacing them 18 inches to 3 feet apart provides sufficient air circulation and room for the deep root system to expand.