Tickseed (Coreopsis) is a popular perennial known for its daisy-like flowers that bloom throughout the summer. Native to North America, it is valued for its adaptability and drought tolerance. Its reputation for spread varies significantly depending on the species, leading gardeners to often ask if it will aggressively take over a space.
Primary Spreading Mechanisms of Tickseed
Coreopsis colonizes new areas using two primary biological methods: self-seeding (sexual reproduction) and vegetative spread (asexual reproduction). Self-seeding occurs when the plant completes its flowering cycle. Spent flower heads mature into small, dark, rounded seeds—which give the plant its common name, tickseed. These seeds are dispersed by wind, water, or gravity.
Vegetative spread relies on specialized underground stems called rhizomes. These horizontal stems grow outward from the main plant crown, generating new shoots and roots at nodes. This process creates a dense, widening clump. The speed and distance of this spread differ greatly among the various types of Coreopsis.
How Different Varieties Spread
Spreading intensity is linked to the species or cultivar, which fall into two growth habits. Clumping varieties, such as Coreopsis grandiflora (‘Early Sunrise’), spread slowly, if at all, using short, tight rhizomes. These types expand by gradually increasing the size of the central root ball and may require division every few years to maintain vigor. While they may self-seed, the resulting seedlings are usually easily managed.
Running or aggressive varieties expand rapidly through extensive rhizome systems. Coreopsis verticillata (threadleaf coreopsis), including cultivars like ‘Moonbeam’ and ‘Zagreb,’ forms large colonies. Other aggressive spreaders include Coreopsis rosea and C. tripteris. These vigorous species are better suited for large, naturalized areas where their assertive nature is less of a concern.
Controlling Unwanted Growth
Controlling spreading Coreopsis requires addressing both self-seeding and vegetative growth. To halt self-seeding, the most effective action is deadheading—promptly removing spent flowers before they form mature seeds. Deadheading prevents seed dispersal and encourages the existing plant to produce more flowers. For large plantings, shearing the entire plant back by up to half its size after the first major flush of blooms accomplishes the same goal quickly.
Controlling vegetative spread requires physical intervention to contain the rhizomes. Aggressively running varieties should be divided every two to three years, preferably in early spring or fall. Division involves digging up the clump and removing the outer, younger sections of the root ball. For highly aggressive types, installing a physical barrier, such as plastic or metal edging sunk into the soil, helps prevent rhizomes from spreading outside a designated area.