Black-Eyed Susans (Rudbeckia hirta) are classic North American wildflowers known for their bright yellow petals and distinctive dark centers. As a self-seeding annual or short-lived perennial, saving the seeds is an economical way to ensure these vibrant blooms return yearly. Collecting seeds allows you to propagate the plant efficiently, whether expanding a meadow or refreshing flower beds. Careful timing and preparation ensure a high yield of viable seeds for the next growing season.
Identifying Ripe Seed Heads
Timing the harvest correctly is essential, as harvesting too early results in non-viable seeds. Maturity begins after the petals drop and the central cone, which contains the seeds, starts changing color. This usually occurs in late summer through mid-October, about three to four weeks after the flower first bloomed.
The cone must transition from a green or spongy state to a dark brown or black color, becoming hard and dry. The supporting stem should also be dried out and brittle. A simple test for ripeness is to gently shake the seed head; if you hear a slight rattling sound, the tiny, dark, mature seeds are ready for release.
Harvesting and Extracting Seeds
When seed heads are mature and the weather is dry, use sharp shears to cut them off, leaving a short length of stem attached. Immediately place the severed heads into a paper bag, jar, or bowl to prevent loose seeds from scattering. A single plant can produce hundreds of seeds.
The seeds are tightly embedded within the cone’s spines and require physical action for release. After ensuring the heads are fully dried, extract the seeds by rubbing the cones vigorously between your hands or over a bowl. Alternatively, place the heads in a sealed jar with a small, hard object, like a coin or a bolt, and shake forcefully to dislodge them. This action separates the tiny, charcoal-gray to black seeds from the dry floral debris known as chaff.
Preparing Seeds for Long-Term Storage
After extraction, the mix of seeds and chaff must be cleaned and thoroughly dried before storage to prevent mold and rot. Cleaning, or “chaffing,” involves separating the small, heavy seeds from the lighter plant material.
You can use a fine-mesh sieve to filter the mixture, allowing the seeds to fall through while retaining larger cone debris. Another effective method involves pouring the seed mixture from a height in front of a gentle fan; the lighter chaff blows away while the heavier seeds drop into a container.
Once clean, spread the seeds in a single, thin layer on a paper plate, screen, or newspaper. Allow them to dry completely for one to two weeks in a cool, dark, and well-ventilated area, avoiding direct sunlight. This final drying step prevents storage failure and viability loss caused by residual moisture.
Optimal Storage Conditions
To maintain seed viability, the storage environment must be cool, dark, and dry. Seeds store best at consistently low temperatures, making a refrigerator, typically the vegetable crisper drawer, an ideal location. Cool storage slows the natural degradation process of the seed’s internal structure.
Use an airtight container, such as a small glass jar or a sealed plastic bag, to protect the seeds from fluctuating humidity. Include a small desiccant packet or powdered milk wrapped in tissue to absorb any remaining moisture. Always label the container clearly with the plant name (Rudbeckia hirta) and the date of harvest, as germination rates decline over two to three years.