Dead shrubs are naturally-generated on the surface in temperate biomes. They look like tiny, shriveled trees.
How to Obtain
This item cannot be obtained as it is into player inventory. If you mine a dead shrub, you don't get a dead shrub, you get flax.
How to Use
Flax is useful, but dead shrubs, in and of themselves, are not. You can't even use them as decoration because they can be mined even if protected.