Dead Bush

Dead Shrubs are blocks that were added in Beta 1.6, and should not be confused with Tall Grass, though a non-naturally-occurring variant of Tall Grass looks visually identical to Dead Shrubs. Shrubs are not a solid block, but rather an aesthetic weed that does not block movements, like Sugar Cane, Wheat and Tall Grass.

Dead Shrubs will only spawn on Sand blocks in desert biomes, and do not produce any resources when broken.

The dead shrub texture seems to be a sapling with its leaves removed

Trivia

 * Shrubs can only be harvested by using an Inventory Editor.
 * Shrubs will not produce any useful resource.