Seeds come in many shapes and sizes. Some are fat and round, while others are long and skinny. But regardless of their size, seeds require proper treatment if you plan to save them from year to year. For those of us who save fruit, herb and flower seeds from our gardens, it’s important to learn how to dry seeds to ensure your chances of success.
Below, you’ll find three seed-drying techniques to prolong the life of your seeds and keep them from developing mold or rot while in storage. But before we dive into these techniques, it’s important to understand why properly drying seeds is so critical.
Why Dry Seeds Before Storage?
Each seed, no matter which plant species it comes from, contains the same things: an embryonic plant that consists of the initial leaves (cotyledons) and the initial root (radicle), the endosperm (food for the newly germinated plant) and the seed coat. While seed coats are designed to keep the embryonic plant and its food source well protected, they aren’t an impenetrable fortress. Seed coats can crack if the seeds are kept too dry in storage. Conversely, they can rot or develop mold if kept in conditions that are too damp. Both of those issues can lead to a limited shelf-life and a reduction in seed viability.
Learning how to dry seeds involves allowing the ideal amount of moisture to evaporate from the seed without it becoming too dry. While the ideal moisture content varies from species to species, most require a moisture retention rate between 5 percent and 8 percent. Seed companies and long-term seed storage facilities can dry seeds to the exact required moisture content level, but for home gardeners, it’s all an educated best guess. The trick is to try them well, but not completely.
Here are three techniques for success when drying seeds.
1. How to Dry Seeds in Open Air
The first seed-drying method requires no special tools or equipment. Once the seed pods or fruits have been harvested from the plant, crack them open and collect the seeds. If the seeds came from a “wet” fruit or vegetable, such as a cucumber, tomato, pepper or squash, wash off the “slime” according to these instructions. If the seeds came from a “dry” seed pod or capsule, like a zinnia, marigold, parsley or cosmos plant, you can skip this step.
Once the seeds are free from their pods or fruits, spread them out on a coffee filter, wax paper or a fine window screen laid on a flat surface in a dry, cool room. Do not use paper towels or newspaper if the seeds are wet. They’ll stick to it and be nearly impossible to remove later.
Spread the seeds out over the area so they don’t touch. Let the seeds rest for a week to ten days before gently stirring them with your finger or a small spoon. Let them dry for another two to three weeks. At this point, they should be dry enough to put into storage.
2. How to Dry Seeds in a Paper Bag
When it comes to learning how to dry seeds, gardeners can’t forget how useful a simple brown paper lunch bag can be. This technique is best used for dry seed pods and capsules, but it should not be used for saving seeds of wet fruits, such as tomatoes, squash, peppers, melons and the like. I find it especially useful for flower seeds and for dry vegetable and herb seeds borne on stalks, like those from lettuce, carrot, spinach and dill plants.
For this seed-drying method, harvest the entire flower head or stalk soon after the flowers are spent. Put the flower stalk into a brown paper bag, top end first, allowing the cut stem end to stick out of the bag’s opening. Place the open paper bag on a table or tray in a dry, cool room with the stem end sticking up. If the bag is top heavy, you can also lay it on its side. Allow the stem to fully die and turn brown in the bag over the course of two to three weeks.
Once the stem is brown and dry, reach into the bag and use your fingers to pull the seeds out of the dead flower head or seed capsule. For some seeds, you might have to crack the seed pod open. The seeds will fall out into the bag and collect at the bottom. Pull out any non-seed materials, such as the plant stems, dried up petals and chaff, and discard it.
After the seeds are collected in the bottom of the bag, leave the open bags sit in the room for another two to three weeks, shaking them occasionally to stir up the seeds. When that time passes, your seeds are now ready for storage.
3. How to Dry Seeds With Silica Gel
Silica gel is a granular substance that pulls and absorbs moisture from the air. You’ll often find little sachets of it in shoe boxes and purses when making a purchase from the store. Loose silica gel is available from craft stores and is very useful when it comes to drying seeds.
To dry seeds using silica gel, prepare the seeds accordingly to separate them from their fruits or pods. Once the seeds are separated, weigh them. Place the same amount by weight of silica gel into the bottom of a glass screw-top jar. Place a small piece of screening on top of the silica gel and then place the seeds on top of the screening. Spread them out as much as possible so they sit in a thin layer. Put the lid of the jar and keep it sealed for 7 to 10 days. Large seeds, like squash and pumpkins, might need a few more days.
Once that time passes, open the jar, remove the seeds and store them appropriately.