Coreopsis, commonly known as tickseed, is a popular group of flowering plants encompassing both annual and perennial varieties. Gardeners favor them for their bright, daisy-like blooms and long flowering season. These North American native plants are low maintenance and thrive in sunny, well-drained locations. Coreopsis plants actively spread and multiply, but the degree and mechanism of this expansion vary widely depending on the specific species or cultivar planted. Understanding the plant’s propagation method is necessary for successful long-term management.
Mechanisms of Coreopsis Spread
Coreopsis utilizes two distinct biological strategies for propagation, meaning its spread is not uniform across the genus. Many varieties, particularly annual types and some perennials like Coreopsis grandiflora, multiply through self-seeding. Once the summer bloom period ends, spent flowers mature into small, dark seed capsules that resemble a tick, giving the plant its common name. These seeds drop into the soil, leading to new plants appearing the following season, often resulting in a larger, naturalized patch.
The second primary method of expansion, common in many perennial species, is through underground runners, known as rhizomes. A rhizome is a horizontal, modified stem capable of producing new shoots and roots. Varieties that utilize this clonal growth method expand horizontally as the rhizomes push out new plants from the original clump. This process physically widens the established plant mass, causing the clump to become denser and larger each year, which may necessitate periodic division to maintain vigor.
Varietal Differences in Growth Habit
The Coreopsis genus contains a wide array of species, and their growth habit is linked to the intensity of their spreading behavior. Tidy, “clumping” varieties, such as Coreopsis grandiflora (Large Flower Tickseed), tend to form a dense crown and expand slowly. While these types can spread by self-seeding, their root systems remain in a cohesive clump, making them easier to manage in a formal garden setting. Cultivars derived from C. grandiflora are favored for their contained growth habit.
In contrast, other species are much more vigorous, primarily utilizing their rhizomatous root structure. The threadleaf Coreopsis (Coreopsis verticillata), and popular cultivars like ‘Moonbeam’ and ‘Zagreb’, are classic examples of this running habit. These varieties are highly effective at forming dense stands because their underground runners can spread aggressively through the soil. For gardeners seeking groundcover, this spreading tendency is a benefit, but in a confined border, these rhizomatous types require active management to prevent them from overtaking nearby plants.
Managing and Controlling Coreopsis Growth
For gardeners who wish to limit the spread of their Coreopsis, specific actions can control both seed and rhizome propagation. To control self-seeding, the most effective method is deadheading. This involves removing the spent flower heads before the seeds fully mature and drop. Snipping off the wilted blooms redirects the plant’s energy away from seed production and back into creating new flowers, extending the bloom season while preventing unwanted seedlings the following year.
Managing the spread from underground rhizomes requires physical intervention, typically through division. Coreopsis plants that spread clonally, such as C. verticillata varieties, may need to be dug up and separated every three to five years to prevent overcrowding and maintain health. The best time to divide the clumps is in the early spring or fall. A sharp trowel or shovel can be used to split the mature plant into smaller sections, each with a healthy root mass. These divided sections can then be replanted or disposed of, effectively resetting the plant’s footprint. Conversely, to encourage spread, gardeners can allow spent flowers to remain for self-seeding or intentionally divide and replant rhizome sections in new areas.