Harvesting seeds from your watermelons and okra is easy -- read on for tips and how-to.... Pick seeds on a warm, dry day to prevent mold and be sure to mark your seed plants as soon as you decide you will be harvesting from them. Seeds should remain in their natural pod or husk until dry, hard and brittle. Small seeds should be stored in a fine mesh bag or paper bag. Don't use plastic bags because it advances mildew. You can also spread the seeds on newspapers or fine screen to increase ventilation.