The cheerful, bright yellow blooms of the Black-Eyed Susan, belonging to the Rudbeckia genus, are a popular addition to garden beds and meadows across North America. The genus includes varieties that behave differently, which dictates the best method for creating new plants. For instance, the widely cultivated Rudbeckia hirta is generally an annual or biennial, meaning it is best propagated by seed. Conversely, perennial varieties like Rudbeckia fulgida return reliably year after year and respond well to root division. Understanding these life cycles allows a gardener to choose the most efficient technique for multiplying these flowers.
Propagation Through Seed Sowing
Starting Black-Eyed Susans from seed is the most common method, particularly for the annual and biennial types. Seeds are ready for collection a few weeks after the petals drop, when the central cone becomes dry and brittle, and the nutlets inside turn a deep charcoal gray or black color. Once collected, the seeds of R. hirta can be sown directly outdoors in late fall or early spring, as they generally do not require a cold period to break dormancy.
If trying to maximize germination rates, seeds can be given a period of cold stratification for about three months at temperatures around 40°F. For an earlier start, seeds can be sown indoors six to eight weeks before the last expected frost date. The tiny seeds need light to germinate, so they should be pressed lightly onto the surface of a moist, sterile seed-starting mix and kept at a steady temperature of 68–72°F. Once germinated, the seedlings require consistent moisture and bright light until they are ready to be moved into the garden.
Increasing Stock by Dividing Clumps
Perennial Black-Eyed Susan varieties, such as Rudbeckia fulgida ‘Goldsturm’, benefit from periodic division. This process rejuvenates the parent plant and prevents the center of the clump from becoming woody and sparse, which can diminish flowering over time. Division is best performed every three to five years when the plant is dormant, either in the early spring as new growth emerges or in the early autumn after the bloom period has finished.
To begin the process, the entire root crown is carefully dug up using a garden fork, making sure to lift as much of the root system as possible. The large clump is then separated into smaller sections using a sharp, clean knife or a spade, or by simply pulling the root sections apart. Each resulting division must contain a healthy portion of the fibrous root system and at least one to two visible growth buds or shoots. The divisions should be replanted immediately into the prepared new locations before the roots have a chance to dry out.
Establishing and Caring for New Plants
The initial care is paramount to successful establishment in the garden. Black-Eyed Susans thrive in a location receiving a minimum of six hours of direct sunlight daily, and they prefer well-draining soil that is moderately fertile. For indoor-started seedlings, a process called hardening off is necessary, which involves gradually exposing them to outdoor conditions over a week before permanent transplanting to prevent shock.
Once placed in the garden, new transplants should be spaced 12 to 18 inches apart to allow for proper air circulation and future growth. Watering needs are highest immediately after planting; newly set divisions and seedlings require a thorough soaking to settle the soil around the roots. Consistent moisture must be maintained during the first few weeks until the root systems are established, after which the plants become more tolerant of dry conditions. Amending the planting hole with compost helps provide structure and initial nutrients, but heavy fertilization should be avoided as it can promote excessive foliage growth at the expense of flower production.