Campari - thanks! I thought of that, too, and I can't remember what DP's objection was. The other thing is that we're not really planting anything else cos we'll be moving in April...but once we have a property we'll start planting up asap!
Maybe you could plant something in a pot so that when you move you can take it with you & it will still be DS's plant.

I can't really help with the other issues but my DS is liking destroying the plants too. He is only 11 months though so slightly different situation.