What is the optimal soil pH range for most ornamentals in Florida landscapes, and which amendment is used to raise pH if needed?

• A. pH 7.5–8.0; add sulfur.
• B. pH 6.8–7.2; add gypsum.
• C. pH 5.0–5.5; add peat moss.
• D. pH 6.0–6.5; lime (calcium carbonate) raises pH.

Answer: (D)

Most ornamentals in Florida landscapes perform best in a slightly acidic to near-neutral soil, around pH 6.0 to 6.5, because this range keeps essential nutrients readily available for plant uptake. Florida soils tend to be acidic, and when pH is too low or too high, nutrient availability shifts—iron and other micronutrients can become less available at higher pH, while some nutrients become less available at very low pH. To raise soil pH when it’s too acidic, lime (calcium carbonate) is used; it neutralizes acidity and adds calcium, helping move the pH toward the desired range. Lime works gradually, so results are not immediate. The other options propose pH levels that are too high for most ornamentals, or use amendments that don’t reliably raise pH (sulfur lowers pH, peat moss lowers pH, and gypsum mainly adds calcium and sulfur without significantly changing pH). Therefore, the best choice is 6.0–6.5 with lime to raise pH.