Grovetender "Photosynthesis" Question

Is it possible to let the Herbling reach several tiers at once? From 0 to 3 in turn one or else?

No, as I understand the ability he’s only supposed to grow once per turn. Took me a while to be able to make a battle last long enough to get my pfp.

Yes, using the Timewalk spell. Especially if it is being multicast. You can also bounce between Herbling and his friends using multiple timewalks, if you can find a way to share it.