Lupines, with their tall flower spikes, are often associated with the classic cottage aesthetic. These perennials are frequently confused with plants that spread aggressively through underground roots, causing concern about them overtaking a flowerbed. Lupines multiply, but their expansion is not through an invasive root system. Understanding how this plant spreads allows gardeners to either encourage a naturalized look or maintain control over their placement.
The Primary Method of Spread: Seed Dispersal
The main mechanism by which lupines expand their territory is prolific self-seeding. After the flower spikes fade, the plant forms long, velvety green pods, each containing several seeds. As summer progresses, these pods dry out and turn brittle brown or black. When fully mature, the pods use explosive dehiscence, forcefully twisting open and scattering the seeds up to 16 feet away from the original plant.
A significant characteristic of this seed dispersal is the genetic variability of the resulting new plants. Seeds from hybrid varieties, such as Russell Lupines, rarely grow “true to type” like the parent. Instead, seedlings often revert to ancestral colors, typically shades of blue, purple, and white, creating a naturalized, multi-colored look. The seeds have a tough outer coat, often requiring cold, moist stratification to encourage successful germination, mimicking the natural winter cycle.
Understanding Clumping Growth Versus Runners
Gardeners often worry that lupines will colonize a space using aggressive horizontal runners, similar to mint or bamboo. However, the perennial lupine has a strong, deep taproot. This single, thick root grows vertically, anchoring the plant firmly and helping it access deep moisture.
The plant grows in a tight, vertical clump from a central crown. While the clump increases in size each year, it does not send out rhizomes or lateral roots to establish new plants nearby. This clumping habit ensures the plant remains contained within its original footprint. The presence of this deep taproot is also why mature lupines tolerate transplanting or division poorly, as disturbing the main root can cause fatal shock.
Techniques for Managing Propagation
Controlling the spread of lupines is straightforward and targets the self-seeding mechanism. The most effective method is deadheading, which involves promptly removing the spent flower spikes after they finish blooming. Cutting the flower spike prevents the plant from producing seed pods, eliminating dispersal.
For gardeners who wish to encourage new plants or maintain a specific color, seeds can be collected manually before the pods burst. This requires monitoring the pods closely and harvesting them when they are brown but still closed and dry. The collected seeds can then be scarified—gently nicked or soaked—to break the hard seed coat, and planted in a desired location.
While lupines are not easily divided, propagation can be achieved by taking basal cuttings from new shoots that emerge near the base of the plant in early spring. This technique is more reliable than dividing the mature crown and produces a genetically identical clone of the parent plant. Division of the main root crown is discouraged, as it often leads to the decline or death of the established perennial.