You recognise these shrubs as twig blights, awakened plants that hide themselves by rooting themselves among ordinary plants.
If your Intelligence (Nature) check is 20 or higher, you also learn that [these creatures are particularly susceptible to fire, given how dry they are].
If you have the Monster Manual, you may read the information on page 31 of that book if your Intelligence (Nature) check is 25 or higher.
If you are currently exploring Area 1, decide your next move after learning this information, then open this spoiler box:
1. Leave the plants alone
The twig blights remain motionless, so you decide there is little reason to disturb the plants.
2. Attack/provoke/burn the plant creatures
They retaliate. Roll initiative and refer to the very first stat block on page 63 of the adventure book.