Undergrowth Hatchling

At the beginning of your upkeep, put a
season counter on Undergrowth Hatchling. Then, if there are four or more season counters on it, remove all season counters
from Undergrowth Hatchling and put a
+1/+1 counter on it.
Undergrowth Hatchling has flying as long as
it has a +1/+1 counter on it.