Catnip (Nepeta cataria) is a perennial herb in the mint family, valued for its aromatic leaves and seeds. Saving catnip seeds from existing plants ensures a fresh supply for future seasons, whether for feline enjoyment or other herbal uses. The process requires careful timing to collect and preserve the tiny, viable seeds. This guide outlines the necessary steps, from identifying mature seed heads to preparing the seeds for long-term storage.
Identifying Mature Seed Heads
Successfully harvesting catnip seeds depends on recognizing when the plant has finished its reproductive cycle. Catnip produces dense whorls of small purple or white blossoms on tall, square stems throughout the growing season. Seeds develop within the calyxes, the small, cup-like structures surrounding the base of the flower.
Wait until the flowers have completely faded and the entire seed head assembly has dried out on the plant. The calyxes, which contain the seeds, will transition from green and soft to a brittle, brown, or gray-brown color. A key indicator of ripeness is a hard, dry texture; the seed heads should feel crispy, and the supporting stems should also begin to turn brown and dry. Harvesting while the seed heads are still green or pliable results in immature seeds that lack the viability to germinate the following season.
Harvesting the Stems and Initial Curing
The ideal time for collection is on a dry, sunny afternoon after any morning dew has fully evaporated. Harvesting dry material minimizes the risk of mold developing during the subsequent curing process. Use sharp shears or scissors to cut the stems several inches below the dried flower heads, collecting only the portions containing the mature seed pods.
Gather the cut stems into small bundles and secure them loosely with twine or a rubber band. Initial curing is necessary to remove residual moisture before extraction. Hang the bundles upside down in a warm, dry location with good air circulation, such as an attic or shed. This curing phase should last one to two weeks, ensuring the calyxes are completely desiccated and ready to release the seeds.
Extracting and Cleaning the Seeds
After the initial curing period, the dried material is ready for threshing—the process of breaking open the seed pods to release the seeds. Place the thoroughly dried catnip stems inside a bucket, a large paper bag, or spread them on a clean tarp. Gently crush, rub, or beat the dried flower heads to dislodge the tiny seeds from the brittle calyxes.
Catnip produces very small, dark brown or black, oval-shaped seeds. Gentle rubbing between your hands or lightly crushing the material with a rolling pin inside a bag is often sufficient to release them. This action creates a mixture of seeds and lightweight plant debris, known as chaff. The next step is winnowing, which separates the heavier seeds from the lighter chaff.
To winnow, use a steady, low-speed breeze, such as the air from a small electric fan. Carefully pour the seed and chaff mixture from one container into another, allowing the stream to pass through the air current. The heavier seeds will fall straight down into the second container, while the lighter chaff is blown away. Repeat this process several times to achieve a clean sample. For the smallest particles, use a fine mesh strainer or kitchen sieve to sift out the remaining debris.
Preparing Seeds for Long-Term Storage
Once the seeds are extracted and cleaned, ensuring they are completely dry is paramount for long-term viability. If moisture is a concern, spread the seeds in a thin layer on a ceramic plate or tray for a few additional days in a dry location. Proper storage relies on maintaining a cool, dark, and consistently dry environment.
The ideal storage condition prevents the seeds from prematurely breaking dormancy or developing mold. Store the clean, dry catnip seeds in an airtight container, such as a glass jar with a tight-fitting lid, or sealed plastic baggies. Paper envelopes can be used, but they must be placed inside a larger, sealed container to protect them from humidity and pests. Label the container immediately with the plant name (Nepeta cataria) and the date of harvest for tracking viability. Storing sealed containers in a refrigerator provides a stable, low-temperature environment that maximizes the length of time the seeds remain capable of germination.