I started saving more seeds this year. Fall it is often quite humid here, and the seed swap wants plastic bags, so this is what I have come up with for getting the seeds nice and dry. Let's hear from you what other systems you are using successfully.
1- collect, dry, and separate the seeds on the kitchen counter, letting them dry for a few days to room humidity.
2- put seeds in paper envelopes, in a big plastic box that closes tightly, with a cat food tin with some DampRid that I got at Lowe's. The bag with the plain powder, labeled for refills, seemed fine and I think cost something like 7$. I put it in an open cat food dish. For myself, I just use paper envelopes, I bought a huge box of them at Staples that are a nice size. I like that moisture will easily pass though the paper, so the seeds will get dryer, and have no risk of mold. The box with seeds and Damp-Rid goes in a cool dark cupboard.
3- for the swap, I bought lots of the little plastic Zip-Lock bags at Michael's. Once the seeds have been in the box in paper envelopes at a very low humidity for a week or more, I figure the seeds are now at about 24% humidity, which is where my box seemed to settle. That is really low, so I figure I can put them in the plastic bags now. Then they go back in the plastic box in the cupboard, waiting for trade day.
4- I have an old temperature/humidity monitor I put in there to see what happened. Right now at Lowe's in the garden section these are on sale for $10, but I think you can truly do without this, and just assume this is working. i found that opening the box briefly even several times a day does not raise the humidity in there except very temporarily and just a few percent. I think it would take time for the paper and seeds to extract enough moisture from the air to matter much.
5- If you have kids or other household members that might tip the box over, you might find a more secure way to put the powder in, but for me the cat food can works fine. I have also heard that buying the DampRid is not necessary, one can use dry powdered milk, maybe I will play around with that but I think it might work fine.
Here are some photos of my setup, complete with lots of seed packets, in both paper and plastic. You can see I keep my purchased seed packets and ones received in trades all together in the box. I bought a big enough box for everything.
