Doesn't look like anyone's mentioned this yet, but it's a biggie;

You can still dodge at full speed while tarred and still have your I-frames. This knowledge has saved me quite a few times in the instances where I get tagged by an unexpected growth add. If you get tagged, and there are multiple growths, try to keep track of which order they may be firing in if they aren't all synced up and listen for them to fire another volley. Another possible lifesaver is knowing they do primarily poison damage, so poison resistance mead or the root mask mentions above should help out quite a bit.

They make a distinct squelching noise just before they fire which will be your cue to dodge to the side and if you can manage you stamina well enough( and they aren't too staggered for firing), you'll have a pretty good chance of breaking free, just keep an ear out for them to broadcast their attack.

Definitely while in or near plains, keep your head on a swivel at all times, granted this advice tends to apply more often to deathsquitos, but still, those growths have a deceptively large detection range and will come over to say hi if you're ♥♥♥♥♥♥♥ around nearby.

Another point to add is "defusing" the tar pits so later exploration should be less of a problem; make use of those shrubs and tree in the area to collect wood for a work bench; once you've cleared the initial complement of growths from a pit, plop a work bench or two on the edges of the pit to prevent future spawns for as long as the benches are intact, and afterwards, if needed you can drain the pit for a big cache of tar should you so desire.