The answer to 'why is my hedge thin grass' is that there are several common causes, including inadequate sunlight, poor soil conditions, or improper watering and maintenance. Thin, patchy grass in a hedge can be a sign of stress and unhealthy growth.
One of the main reasons for thin grass in a hedge is lack of sunlight. Hedges and shrubs can create dense shade that prevents the grass from getting enough sunlight to thrive. This is especially common in older, overgrown hedges. Improving light exposure by trimming back the hedge can help the grass fill in.