Certified Professional Horticulturist (CPH) Practice Exam

What is an essential benefit of using pine bark and compost as mulch around ornamentals?

1. Enhances soil acidity

2. Provides nutritional support for roots

3. Helps retain soil moisture

4. Attracts beneficial insects

The correct answer is: Helps retain soil moisture

Using pine bark and compost as mulch around ornamentals primarily helps retain soil moisture. This characteristic is vital for maintaining healthy plants, especially during dry periods. Mulching with organic materials like pine bark and compost creates a barrier that reduces water evaporation from the soil surface, keeping moisture levels consistent. Furthermore, it can improve soil structure as it breaks down over time, enhancing water infiltration and retention. While compounds like pine bark can contribute to soil acidity as they decompose, their primary role as mulch is moisture retention. Similarly, while they may provide some nutritional benefits as they break down or attract certain beneficial insects, those are secondary effects compared to the immediate and critical impact of moisture retention. Hence, the essential benefit remains the capability to help retain soil moisture around ornamentals, promoting healthier plant growth.