Solomon’s Seal (Polygonatum species) is a perennial plant known for its gracefully arching stems and bell-shaped flowers. This plant does spread, but typically in a manageable fashion. Its growth habit is less aggressive than many groundcovers, yet it is vigorous enough to form attractive colonies over time. Understanding how this perennial expands its footprint is key to effective garden management.
The Mechanism of Spread: Rhizomes and Seeds
The primary method of propagation is through underground stems, known as rhizomes. These thick, white, fleshy structures grow horizontally beneath the soil surface, slowly creeping outward from the main plant. As the rhizome grows, it develops dormant buds, and each year a new arching stem of foliage emerges from one of these buds, gradually increasing the size of the plant’s colony.
The rhizomes serve as storage organs for water and nutrients, allowing the plant to colonize an area steadily by vegetative reproduction. Seed propagation is a secondary and much slower method of expansion. The plant produces blue-black berries in the fall that contain seeds, which are typically dispersed by birds or small mammals. These seeds require a long period of dormancy and stratification before they can germinate, often taking two to three years to sprout, making rhizome expansion the dominant concern for gardeners.
Comparing Spreading Habits of Common Varieties
The rate at which Solomon’s Seal spreads depends on the specific species or cultivar planted. The native North American species, such as Polygonatum biflorum (Smooth Solomon’s Seal), tends to be the more vigorous spreader. This variety uses its rhizomes to colonize woodland areas, forming dense patches that spread aggressively in ideal conditions. P. biflorum can expand its territory by up to a foot or more per year once established.
In contrast, the popular ornamental cultivar Polygonatum odoratum ‘Variegatum’ (Fragrant Solomon’s Seal) exhibits a much slower rate of spread. This variegated form is clump-forming, meaning its rhizomes remain tighter to the original planting location. This slower, contained growth makes the fragrant variety a favored choice for smaller garden beds or formal borders where containment is a priority. Gardeners should select their variety based on whether they desire a fast-filling groundcover or a restrained perennial accent.
Strategies for Controlling Spread in the Garden
For gardeners wishing to manage the spread of Solomon’s Seal, the plant’s rhizomatous nature provides several clear and effective control methods. The most common practice is routine division of the clumps every three to five years. This is best done in the early spring, just as new shoots are emerging, or in the fall after the foliage has died back. Digging up the established clump and slicing off sections of the rhizome limits the plant’s size and simultaneously provides new plants for other areas of the garden.
Another effective physical control method is the use of root barriers, which can be installed around the planting area to contain the creeping rhizomes. Alternatively, planting the Solomon’s Seal within a container that is then sunk into the ground can achieve the same containment for more aggressive types. The growth rate can also be moderated by careful site selection. Although Solomon’s Seal thrives in rich, moist soil, planting it in slightly drier or less fertile soil naturally slows the speed of its rhizome expansion.