Leftover seeds and seeds harvested from heirloom and other favorite flowers and vegetables should be stored in a sealed paper or plastic envelope, and labeled clearly to ensure that they will be ready to be planted another day. Whether you keep the seeds for your own supply, trade them for others' seeds or give them as gifts will determine what kind of paper or other material you use to make your homemade seed envelopes.
Match Envelope and Seed Types
First, assess your needs. Large seeds need larger envelopes, and smaller seeds require that the envelopes have no gaps at the corners through which the seeds would slip out. If you want to give your seeds as gifts, you'll want an attractive envelope, but economical envelopes fashioned from recycled materials suffice for seeds you save for your own use.
One of the easiest ways to make seed envelopes is to fashion a business-sized envelope into three seed packets. Choose business envelopes with an oblong, rather than a triangular-shaped flap. Self-sealing envelopes are a much safer choice than the lick-and-seal type, too: Many seeds are toxic, so it's much safer to avoid putting the seed-filled envelope anywhere near your mouth. One business-sized envelope, cut vertically into thirds, will make three seed packets. Seal up the sides with tape or glue, and secure the flaps at the top after you pour in the seeds. If you have a computer with envelope-printing software and a printer, design and print custom labels (three across, on the address side of the envelope) before you cut the envelope. If you can find foil-lined envelopes (they're sometimes sold around the holidays), they would make even sturdier packets and would block some moisture, as well, keeping the seeds even fresher.
Some seeds are so routinely infested with bug pests that it's wisest to package them in a clear packet so that you can keep an eye on what's going on inside. Hollyhock seeds saved from your garden almost invariably have some weevils mixed in, so a small, zipper-topped sandwich bag would work for such seeds.
European seed savers use a clever origami-like folded seed packet that they fold out of paper. You'll find a link to the pattern and instructions ("Glueless and Tapeless Seed Packets") listed in the Resources section below. Make them of foil paper for a prettier packet, or reuse pages from seed catalogs for a whimsical envelope.
Repurposed paper and other materials make very useful seed packaging. Fold and tape them into square envelopes, leaving a little flap on the top to seal after you drop in the seeds. Just take care that no one will mistake a seed packet of reused food packaging as a package of consumable snacks: Some seeds have a nut-like appearance, and some are very toxic.
Use junk-mail business reply envelopes as-is to store seeds (just don't lick the flap to seal them; use tape), or cut them into smaller packets, as outlined above.
Finally, if you want to make a particularly nice, customized seed packet, use a template to print your own seed packets onto the paper of your choice using your computer, graphics design or word processing software, and a printer. "Seed Envelope Templates," also listed in Resources below, features several ready-to-print templates for printing seed packets.