So, the party was accompanying a small group of traders along a road. The road was at one time a couple of centuries ago well-developed and maintained, but now has crumbled away in places and narrowed. The party comes to a point where the whole remaining road is covered for about thirty feet with teal-colored spade-leaved vines that are unidentifiable. At this point, a small footpath/stock trail leaves the road and loops around the vines, rejoining the road on the other side. On the opposite side of the footpath, there's a large growth of carrot/asparagus fern like plants, maybe 15' across.
These are burrow tubers! Crossing on the footpath of course means the plants discharge spores. The party's elf checked the vines quite carefully, but they all ignored the carrots. To their peril! The dwarf and elf made their saving throws, but one of the traders failed and started digging. The dwarf rashly tried to grab the trader and pull him away and of course tanked this save. So, the dwarf and trader both kept burrowing while the party wondered what to do. Once the tubers were eaten, they decided to hurry on to the town a couple hours up the road. After an hour the dwarf and trader started eating dirt, which was enough to convince the party (they're very low level) to use their potion of neutralize poison (quietly) on the dwarf. This worked, but of course the trader is in a bad way.
It was really great, and the dwarf's player almost immediately said "if I grow carrots in my stomach I'm gonna be mad". Saw it coming I guess
Highly recommended encounter! Also, I threw a red herring plant encounter in earlier in the evening, no big deal just some dead trees and vines and an abandoned wagon. Once you start including dangerous vegetation in your games, be sure to include many other plant descriptions/encounters so the party is not immediately on high alert every time you start describing vines or tress.
