Mother Earth News, Sep/Oct 1987
Care and Handling
By Nancy Bubel
No matter what kind of seed you're collecting, be sure to pick it when it's dry, not green. Green seeds may contain incompletely developed embryos or may lack sufficient endosperm (stored nourishment) to survive until planting time. Green seed is also more likely to spoil in storage. (If you bag heads of plants that ripen their seed gradually, cut a few slits in the bag for better air circulation.) If at all possible, gather seeds on a dry, sunny day - and preferably before the weather gets too cold. Frost itself won't hurt most seeds, but the condensation of moisture caused by alternate freezing and thawing might shorten their useful life span.
Even seeds that look and feel dry when you pick them should be spread on newspaper to air-dry for up to a week before packaging. Large seeds like beans and corn benefit from several weeks of air-drying before storage. Never dry seeds in an oven. Prolonged temperatures over 95°F can damage or kill them. And be sure to label your seeds as soon as you can after collecting them, so you don't mix them up during the drying process.
Beans and many grain seeds must be threshed to knock off the pods. You can eliminate much of the chaff - pieces of broken pods, leaves and stemsthat remains by winnowing. To accomplish this pleasant harvest ritual, pour the seed several times from one container to an other in a stiff breeze or in front of a fan. The light, dry stuff will blow away as the heavier seed falls straight down.
The general rule is, if the seed is green, wait. I had peas that looked completely dead but the pods were still green and soft for two weeks. My beans are the same way now. You can pull the whole plant and hang them up to dry (if the plant stem is completely dry and dead, not processing fluids), but if you aren't needing the space for anything else right away, just wait until the seeds dry out naturally. The absolute best way to dry seeds is the way nature intended, in the sun! In the absence of sunlight, try to emulate it. It's not the UV light that does the trick, its the percolation (evaporation). You could place them under a lamp (regular incandescent or fluorescent light) or even an infrared heat lamp.
If you don't have any of these available, a food dehydrator would work, but be careful about the temperature. I have a dehydrator I purchased from Wal-mart for $40 a couple of years ago and it works fine though it runs at a relatively low temperature (takes longer to dry food than other products out there). It's not thermostatically controlled, but it's fairly easy for me to judge the temperature and I never allow it to run more than a hour or so at a time with seeds. I would not advise using an oven, the temperature control is rather tricky at the low end and it is easy to forget you have them in there and they get too dry!
It is possible to dry out the seeds too much. This can be monitored by not allowing the seeds to get too hot in the dehydrator. How hot is too hot? That's hard to say, if your dehydrator is thermostatically controlled, just use a temperature of no more than 100 degrees (F). If your dehydrator is not thermostatically controlled, don't allow the seeds to sit in there for more than an hour at a time. Turn off the dehydrator and let them cool to room temperature, then check them by picking up a seed and carefully squeezing it to see if it is hard yet. Be sure to check several this way. If the majority are still somewhat soft, dry them for another hour and so on. Above all, be careful.
Offered by Roger.