 Hill says once you've collected the seeds from several plants, package them in something that's breathable so mold doesn't form on the seeds and compromise their viability. I usually advise people to pack them in a paper bag or an envelope and then to double bag that or also put it in a box so that it's not leaking seed because if you're going to be mailing it or transporting it and it is resistant, you don't want to be leaving a trail of resistant seed with you.