Certified Professional Horticulturist (CPH) Practice Exam

You have just identified an accumulation of soluble salts and root desiccation in a customer's container plant. What is the probable cause?

1. Poor watering

2. Improper fertilization

3. A rootbound container

4. Infestation of root knot nematode

The correct answer is: Improper fertilization

The identification of soluble salts accumulation and root desiccation in a container plant suggests that improper fertilization is likely the cause. When a plant is excessively fertilized or receives a high concentration of soluble fertilizers without adequate leaching, salts can build up in the soil medium. This accumulation occurs because the salts in fertilizers do not get washed away, especially in containers where water drainage may be limited. High levels of soluble salts can lead to osmotic stress, making it difficult for the roots to take up water, which ultimately results in root desiccation. The compounds can draw moisture away from the root system, leading to a condition known as physiological drought, even if there is water present in the soil. While poor watering practices, such as infrequent or excessive watering, can also contribute to plant stress, they typically do not create a situation of soluble salts accumulation in the soil unless there is also an element of improper fertilization involved. Other options, such as a rootbound container or root knot nematode infestation, might lead to different symptoms, such as poor growth or visible damage to the roots, rather than the specific combination of soluble salts and desiccation observed.