Certified Professional Horticulturist (CPH) Practice Exam

How can you prevent the buildup of soluble salts in plant containers?

1. Fertilize at lower amounts yet more often

2. Only fertilize plants when they are turgid

3. Allow a small amount to leach out the bottom at each irrigation

4. When leaves begin to curl, stop fertilizing

The correct answer is: Allow a small amount to leach out the bottom at each irrigation

Preventing the buildup of soluble salts in plant containers is crucial for maintaining plant health, particularly in container gardening where salts can accumulate due to limited soil volume and frequent fertilization. Allowing a small amount of water to leach out of the bottom of the pot with each irrigation effectively flushes away excess salts that can otherwise accumulate in the growing medium. When you irrigate, the water carries salts with it as it moves through the medium. If you allow some water to escape and leach out from the bottom, you are essentially creating a mechanism for removing these salts that can harm plant roots and lead to issues such as leaf burn or stunted growth. This practice of leaching is particularly important in containerized plants, which are more susceptible to salt buildup than those grown in the ground where salts can disperse more readily. Using lower amounts of fertilizer more frequently, fertilizing only when plants are turgid, or stopping fertilization when leaves begin to curl may each have their benefits in certain contexts, but they do not directly address the issue of salt accumulation in the same effective way as leaching does.