Certified Professional Horticulturist (CPH) Practice Exam

What is a common sign of root rot in plants?

1. Wilting despite proper watering

2. Bright yellow foliage

3. White growth on the soil surface

4. Brown or black roots

The correct answer is: Brown or black roots

Root rot is a significant issue in plant care, often caused by overwatering or poor drainage, which leads to a detrimental environment for root health. The most definitive sign of root rot is the condition of the roots themselves. When roots are affected, they typically appear brown or black, indicating that they are decomposing rather than healthy and functioning properly. Healthy roots usually have a firm texture and may be white or pale in color. However, as rot sets in, these roots begin to decay, losing their structural integrity and turning brown or black. This visual discoloration demonstrates that the roots are no longer able to perform their essential functions, such as water and nutrient uptake, which can ultimately lead to the decline of the entire plant. While wilting despite proper watering, bright yellow foliage, and white growth on the soil surface can indicate other issues such as nutrient deficiencies, environmental stress, or fungal infections, they are not definitive signs of root rot. The distinct appearance of brown or black roots is the clearest and most direct indicator of this problem.