Certified Professional Horticulturist (CPH) Practice Exam

What is the preferred pH range for most garden plants?

1. 3.0 - 4.0

2. 5.5 - 7.5

3. 7.5 - 9.0

4. 8.5 - 9.5

The correct answer is: 5.5 - 7.5

The preferred pH range for most garden plants is between 5.5 and 7.5. This range is considered optimal for the majority of garden plants because it allows for the best nutrient availability and overall plant health. Within this pH range, essential nutrients such as nitrogen, phosphorus, and potassium are readily accessible to plants, facilitating effective growth and development. At pH levels lower than 5.5, such as in the 3.0 to 4.0 range, nutrient availability can become restricted, and some essential elements may become toxic to plants. Conversely, pH levels higher than 7.5 can lead to nutrient deficiencies, particularly in micronutrients like iron and manganese, as these nutrients become less soluble and more difficult for plants to absorb. Therefore, maintaining a pH within the 5.5 to 7.5 range is crucial for creating a conducive environment for most garden plants to thrive, making it the correct answer for preferred pH levels.