Trample
{3}{G}: Conifer Wurm gets +X/+X until end of turn, where X is the number of snow permanents you control.
Because Conifer Wurm is itself a snow permanent, its ability will usually give it at least +1/+1.
The value of X is determined only as Conifer Wurm’s ability begins to resolve. It won’t change later in the turn if the number of snow permanents you control changes.