The original research that formed the basis for the One-Third Rule was done on?

• A. Warm-season grasses
• B. Cool-season grasses
• C. None of these answers
• D. Bermuda grasses

Answer: (C)

The One-Third Rule comes from how grasses respond to defoliation: removing too much leaf blade at once cuts into the plant’s photosynthetic area and carbohydrate reserves, slowing recovery and increasing stress. The rule — not cutting more than one-third of the leaf blade — is a general guideline tied to the plant’s energy balance and regrowth capacity, not to a specific grass type.

Because the original research behind this guideline examined how grasses in general respond to clipping, it isn’t limited to a particular category like warm-season or cool-season grasses, nor to Bermuda grasses specifically. That broad physiological basis is why the correct answer is that the foundational work wasn’t tied to a single grass grouping. In practice, applying the one-third rule helps maintain health across many turf types, especially under heat or drought when energy reserves are more critical.