What is the typical pH range for most ornamentals in moderately weathered soils?

• A. About 5.5 to 6.5
• B. About 7.5 to 8.5
• C. About 6.0 to 7.0
• D. About 4.5 to 5.5

Answer: (C)

Nutrient availability in soil is strongly shaped by pH. Most ornamentals grow best in a near-neutral to slightly acidic range, around 6.0 to 7.0, especially in moderately weathered soils that buffer the soil solution. In this range, essential nutrients—nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur—are generally accessible to roots, and microbial activity supports nutrient cycling. If pH is too low (more acidic), some nutrients become overly available and others (like phosphorus) can still be limiting or tied up in forms plants can’t use. If pH is too high (more alkaline), many micronutrients such as iron, manganese, zinc, and boron become less available, leading to deficiencies common in ornamentals. Phosphorus also tends to precipitate with calcium at higher pH, further limiting uptake. So, the typical range that supports a wide variety of ornamentals in moderately weathered soils is about 6.0 to 7.0.