The temperature range at a 2-inch soil depth for optimal top growth of warm-season turfgrasses is:

• A. 60-75 F
• B. 70-85 F
• C. 80-95 F
• D. 95-110 F

Answer: (C)

Warm-season turfgrasses respond fastest to growth when the root zone is in the warm-to-hot range, and at about 2 inches depth that optimal zone is roughly 80 to 95 F. In this window, the enzymes that drive cell division and expansion work efficiently, water and nutrient uptake by roots meets the shoot’s demand, and new leaves and tillers develop rapidly, giving strong top growth.

If the soil is cooler, around 60 to 75 F, metabolic rates slow down and growth remains sluggish. Slightly warmer, like 70 to 85 F, still supports good growth but isn’t as productive as the 80–95 F range, which is where warm-season grasses reach their peak top growth. Pushing temperatures much above 95 F (toward 100–110 F) can stress the plants, reduce photosynthetic efficiency, and slow growth or trigger stress responses, so that range is not ideal for maximizing top growth.

So the best range for rapid top growth at that shallow depth is 80–95 F.