Certified Professional Horticulturist (CPH) Practice Exam

Which growing medium formulation should you select for long term use for containerized plants?

1. Equal parts peat moss, vermiculite, and compost

2. Equal parts peat moss, perlite, and sterile topsoil

3. Large amounts of milled pine bark and/or sterilized soil and peat moss plus perlite, ground Styrofoam, or sand

4. Equal parts peat moss, perlite, and milled pine bark

The correct answer is: Large amounts of milled pine bark and/or sterilized soil and peat moss plus perlite, ground Styrofoam, or sand

The selection of a growing medium for long-term use in containerized plants is crucial for providing the right balance of aeration, drainage, and nutrient retention. The recommended formulation, which includes large amounts of milled pine bark and/or sterilized soil and peat moss, along with additives like perlite, ground Styrofoam, or sand, has distinct benefits that make it particularly suitable for extended cultivation. Milled pine bark is known for its excellent aeration and drainage properties. It supports root growth effectively and remains stable over time, which is essential for long-term container plant health. When combined with sterilized soil and peat moss, the medium retains moisture while still allowing for adequate airflow to the roots, preventing waterlogging, which can be detrimental to plants. The inclusion of perlite contributes further to aeration and prevents compaction of the medium, facilitating healthy root development. Ground Styrofoam, while less common, helps decrease weight and improves drainage, and sand can also contribute to better drainage and structure. Overall, the formulation provides a well-balanced growing medium that fosters the long-term vigor and health of containerized plants, making it an ideal choice for sustained cultivation.