Iowa Code § 468.139: Trees and hedges.

When it becomes necessary to destroy any trees or hedges outside the right-of-way of any ditch, lateral, or drain in order to prevent obstruction by the roots thereof, if the board and the owners of such trees or hedges cannot agree upon the damage for the destruction thereof, the board may proceed to acquire the right to destroy and remove such trees or hedges by the same proceedings provided for acquiring right-of-way for said drainage improvement in the first instance.