I'm not really sure how much the terms "dies" befits a permanent, but anyway.
So this is basically to clog the enemies permanent slots. I like the idea. It feels like life's very own way to deal with the matter.
However, I don't think the unupped version is too useful. Every seedling dies in 3 turns and you have (correct me if I am wrong) 13 ok, 16 permanent slots. You need 4 seedlings a turn and four Usangs to limit the number of permanents to 4 (4 will quite likely be there before you set up the combo anyway). 8 earth quanta per round is probably more than I'd be willing to pay, considering that this won't work against weapons and shields (other than normal PC) and is weak against CC. The upped version seems fine, maybe still slightly underpowered? I'd either go for 4 rounds all the way or reduce the unupped one's ability cost.
That being said, a very nice and creative idea.