Greetings, Gardener. We are the Black-eyed Susans (Rudbeckia spp.), and we understand your concern. Our cheerful, golden blooms can indeed become enthusiastic in our pursuit of sun and space. To live in harmony, you must understand our nature. Here is how you can manage our spread from our perspective.
Our primary method of expansion is through prolific seed production. Each of our dark, cone-like centers is packed with hundreds of tiny seeds. As we stand tall through autumn and winter, these seeds are a feast for finches and other birds, who carry them far and wide. Furthermore, we spread locally through rhizomes—underground stems that creep outward from the parent plant, sending up new shoots. To control us, you must address both of these strategies.
The most effective and simplest method to check our spread is to engage with us before our seeds mature. This practice is known as deadheading. As our vibrant petals begin to fade and droop, we are diverting energy from bloom production to seed creation. If you clip off our spent flower heads just below the base of the bloom, you prevent this energy shift and, more importantly, halt the production of thousands of potential new plants. Do this consistently throughout the blooming season, and you will encourage us to put energy into more flowers on the existing plant rather than into creating new generations across your garden.
If our underground advance is the main concern, you can install physical barriers to contain our root system. Sink metal or heavy-duty plastic edging at least 10-12 inches deep into the soil around our clump. This barrier should form a continuous circle, leaving us enough room to grow healthily within our designated area for a few seasons. This method physically blocks our rhizomes from traveling beyond their allotted space, effectively corralling our colonial ambitions without harming the main plant.
Every few years, we become crowded in the center as our outer edges expand. This is your opportunity to manage our size and vigor. In early spring or fall, use a sharp spade to dig up our entire clump. You can then divide us into smaller sections, ensuring each new division has healthy roots and several growing points (eyes). Replant one division in the original location or a new spot and share, compost, or discard the extras. This process not only controls our spread but also rejuvenates us, leading to stronger growth and more abundant blooms on the remaining plants.
We thrive in full sun and well-drained soil. By altering these conditions, you can naturally reduce our vigor. Planting taller perennials or ornamental grasses to our south can limit our sunlight, making us less aggressive. While we are tolerant, consistently wetter soil conditions can also slow our rhizome growth. However, this method requires careful planning to avoid harming other desirable plants in the vicinity that may share similar cultural needs.
