A hem is the first layer of plants of a boundary area or hedge. The latter are ideally composed of three layers:
- a hem;
- a shrubby stratum (bushes, shrubs);
- a tree stratum (trees).
The hem, composed of herbaceous plants, provides the transition between the meadow environment or farm land and the forest environment. Being the easiest layer to degrade, it is one of the first signs of loss of ecological quality in a boundary area or a hedge.
This old hedge has lost its hem and its shrubby stratum. © P. Charpiat, Wikimédia CC by-sa 3.0