Nasturtiums (Tropaeolum majus) are vibrant, easy-to-grow annuals prized for their colorful, edible flowers and leaves, which add a peppery bite to salads. Saving the seeds from your current plants is a straightforward, rewarding process that allows you to cultivate a new generation of these cheerful flowers for little to no cost. This guide outlines harvesting, cleaning, and storing nasturtium seeds, ensuring they remain viable for planting in the next growing season.
Knowing When Nasturtium Seeds Are Ready
Nasturtium plants begin producing seeds once their characteristic trumpet-shaped flowers fade and drop their petals. The initial developing seeds are large, usually appear in clusters of three, and are soft, plump, and pale green. These immature seeds must be allowed to fully ripen on the plant to ensure they contain a developed embryo capable of germination.
The clearest indicator of readiness is a change in both color and texture as the seeds mature. The green seed pods will gradually turn a light yellow, beige, or tan color, simultaneously hardening and shriveling slightly. The seeds are naturally designed to drop from the plant when they reach this fully mature state, often landing directly onto the soil beneath the foliage.
The best method to check for readiness is to gently touch the seed pods, especially those that have begun to turn pale. If the seed comes away from the stem with a light touch and no tugging is required, it is ready for collection. Attempting to pull off a seed that resists separation means it is still immature and should be left to continue ripening.
Collecting and Cleaning the Seeds
Collecting involves gently plucking mature, detachable seeds from the plant or gathering those that have already dropped. Search the soil directly beneath the plant’s canopy, as the heavy, ripe seeds often roll just a short distance from where they fell. Harvest before heavy rain or a deep frost, which can damage the seeds or cause them to rot on the damp ground.
Once collected, the seeds require a curing process to reduce their internal moisture content. Spread the harvested seeds in a single layer on a paper plate, a screen, or a sheet of newspaper, ensuring none are touching. Place the spread-out seeds in a cool, dry, and well-ventilated location away from direct sunlight.
This initial drying period should last for one to two weeks, or even longer for any seeds that were still slightly green upon collection. Proper curing prevents mold growth and prepares the seed for long-term dormancy by reducing the risk of premature germination in storage. The seeds are fully cured when they feel hard and dry to the touch and the color has uniformly changed to a tan or light brown.
Proper Storage for Viability
After the seeds are cured and dry, prepare them for storage to maintain their ability to sprout next season. Store the dried nasturtium seeds in an environment that is dark, cool, and consistently dry throughout the winter months. Exposure to fluctuating temperatures or high humidity can prematurely end the seed’s dormancy.
Airtight glass jars or small paper envelopes are excellent containers for long-term seed storage. If using paper envelopes or small paper bags, place them inside a secondary, sealed container to protect them from pests and excessive moisture. Always label the container clearly with the seed variety and the year of harvest to keep track of its age.
Nasturtium seeds stored under these ideal conditions can remain viable for planting for approximately three to five years. However, their germination rate is highest when they are planted the following spring, offering the best chance for a successful crop. Placing the sealed, labeled container in a refrigerator can further extend the seed’s viability by providing a consistently cool and stable environment.