Certified Professional Horticulturist (CPH) Practice Exam

When selecting perennials, which factor is important for determining its growth?

1. Availability of seeds

2. Soil pH

3. Flower color

4. Growth rate

The correct answer is: Soil pH

Soil pH is a critical factor when selecting perennials because it significantly influences plant health and growth. Different plant species thrive in specific pH ranges, which can affect nutrient availability in the soil. For instance, some plants prefer acidic soils (pH less than 7), while others favor alkaline conditions (pH greater than 7). If the soil pH is not suitable for a particular perennial, it may struggle to absorb essential nutrients, leading to poor growth or even plant failure. Therefore, understanding and adjusting soil pH is crucial for ensuring that perennials can establish themselves and flourish in a given environment. While other factors like the availability of seeds, flower color, and growth rate are relevant to plant selection, they are not as fundamental to the plant's growth potential as soil pH. Availability of seeds pertains more to sourcing and buying the plants rather than their growth once established. Flower color is primarily a matter of aesthetic preference and does not impact the biological aspects of growth. Growth rate can be an important consideration, but it often depends on other factors such as environmental conditions and, crucially, the suitability of the soil pH for the species in question.