Don't use it on the enemies, use it on your creatures and buff them!
Every time it does the two steps. Let's say you use it on a FFQ, many times, unupped version.
Turn 0, you play FFQ 3/7 and Seed Dibber, ability not charged yet.
Turn 1, you Plant, FFQ was 3/7 and becomes becomes 2/5. At the end of the turn, it gets +1/+1, so 3/6.
One seed on FFQ.
Turn 2, you Plant, FFQ was 3/6 and becomes 2/4. At the end of the turn, it gets +2/+2 from 2 seeds, so 4/6.
Two seeds on FFQ.
Turn 3, you Plant, FFQ was 4/6 and becomes 3/4. At the end of the turn, it gets +3/+3 from 3 seeds, so 6/7.
Three seeds on FFQ.
Turn 4, you Plant, FFQ was 6/7 and becomes 5/5. At the end of the turn, it gets +4/+4 from 4 seeds, so 9/9.
Four seeds on FFQ.
Turn 5, you Plant, FFQ was 9/9 and becomes 8/7. At the end of the turn, it gets +5/+5 from 5 seeds, so 13/12.
The oldest seed has given +1/+1 5 times now, so it stops. There were 5 but one affected for the last time, so 4.
Turn 6, you Plant, FFQ was 13/12 and becomes 12/10. At the end of the turn, it gets +5/+5 from 5 seeds, so 17/15.
The oldest seed has given +1/+1 5 times now, so it stops. There were 5 but one affected for the last time, so 4.
Turn 7, you Plant, FFQ was 17/15 and becomes 16/13. At the end of the turn, it gets +5/+5 from 5 seeds, so 21/18.
The oldest seed has given +1/+1 5 times now, so it stops. There were 5 but one affected for the last time, so 4.
Turn 8, you Plant, FFQ was 21/18 and becomes 20/16. At the end of the turn, it gets +5/+5 from 5 seeds, so 25/21.
The oldest seed has given +1/+1 5 times now, so it stops. There were 5 but one affected for the last time, so 4.
And then I get bored and leave what happens next to you.
All of this has cost you 26 Life quanta (2 initial 8x3 ability) and 6 Air for FFQ, as well as 8 turns not counting the one you play both things. FFQ hasn't lost her ability for the whole time and could have been spawning Fireflies.
As you can see, the lowest HP you could obtain was 4 after two consecutive uses. That's just 3 less than there was before, so it is not suited for creature control. And it costs 6 Life to use the ability two times, so... not worth it, really.
Upped version probably looks similar, but CBA.