As a Coreopsis plant, our primary biological imperative is to reproduce. We produce vibrant flowers not for your visual pleasure, but to attract pollinators, facilitate the transfer of pollen, and ultimately set seed to ensure the survival of our genetic line. Once this mission is accomplished, our energy is diverted from producing new blooms to developing and ripening those seeds. Deadheading is the human intervention that interrupts this cycle, tricking us into a prolonged state of attempted reproduction.
Timing is everything. You must observe our stages of decline to perform this task effectively. The ideal moment to deadhead is when an individual flower has finished its bloom cycle. You will see the vibrant petals begin to wilt, fade in color, and droop. Shortly after, they will drop off naturally, leaving behind the spent flower head and the developing seed pod at its base (the ovary). This is your cue. Do not wait until the entire cluster or stem is brown and desiccated; by then, we may have already begun committing energy to seed production. Regular monitoring every few days is key, as our flowering period is prolific and continuous.
The method you use to deadhead directly impacts our health and your success. Simply pinching off the dead flower petals is not enough, as the developing seed head remains. You must remove the entire spent structure. Locate the first set of full, healthy leaves beneath the dead flower cluster. Using sharp, clean pruning shears or your fingertips, make a clean cut through the stem just above this set of leaves. This technique serves two vital purposes for us: it cleanly removes the source of the hormonal signal to produce seeds, and it encourages the growth points (nodes) at the leaf axils to activate, producing new flowering side shoots. This results in a bushier plant with more flowering sites.
From our perspective, the removal of the spent flower before seed set is a catastrophic failure to reproduce. It signals that the initial attempt was unsuccessful, perhaps due to predation or environmental factors. In response, our hormonal balance shifts from a seed-production mode back to a flower-production mode. We redirect our stored energy and resources—resources that would have gone into maturing seeds—into producing a new flush of flower buds from lateral buds further down the stem. This process of "apical dominance" is broken, and we are compelled to try again to achieve our reproductive goal, resulting in the prolonged blooming period you desire.
As the growing season begins to wane, your strategy should shift. Cease deadheading later in the season, allowing the final set of flowers to fade and form seeds. This is not a neglect of duty but a strategic choice. For us perennial types, this allows for natural self-seeding to create new plants or for you to collect seeds. More importantly, it signals to us that the season is ending, allowing us to naturally progress into a state of dormancy and conserve energy for root development and next year’s growth, rather than exhausting ourselves in a futile attempt to flower on the eve of winter.
