Flora

Trees are plants that commonly occur in the world. Their appearance changes based on the biome.

Trees can be cut down using a, which will grant and. It is profitable to cut down trees with the chainsaw, as it will always grant more resources than what is needed for one.

Trees cannot be planted and will never reappear, so with enough dedication, all trees could be removed from the world.

Hitbox
Most tree or plants with visible wooden part in their body have hitbox, these can cause obstructions to engineer's and vehicle's movement and also encroach buildings. Engineers sometime can get stuck within a tree, but can be unstuck with a chainsaw or simply clicking 'respawn' in the menu. Some vehicles has the ability to knock down trees as well. When constructing buildings, and when using the auto-snapping mode, by holding down the during placement, the buildings will be automatically moved upwards to avoid small trees, while large trees will disable the building placement.

Bushes, or plants without wooden parts, including flowers, do not have hitboxes, so they will not cause obstructions.

Speculation
As no wooden structures have been seen so far, it is likely only usable as fuel for the Biomass Generator.