Okay, I planted some "spares" on a second character, tucked them in her bank, and logged out. Didn't log the character in for about a week, and logged in today to find all the plants mysteriously gone. No bowls in her bank or backpack, signifying dead seedlings, the plants were just gone. Yet the bag of seeds I'd placed in her bank was still there, and all the seeds I had planted out from that bag are still gone. Curiouser and curiouser!