Certified Professional Horticulturist (CPH) Practice Exam

What is a common sign of over-fertilization in plants?

1. Stunted growth with dark green leaves

2. Burnt leaf edges and leaf drop

3. Rapid growth of stems but small leaves

4. Flowering at inappropriate times

The correct answer is: Burnt leaf edges and leaf drop

A common sign of over-fertilization in plants is indeed burnt leaf edges and leaf drop. This condition occurs when excessive nutrients, particularly nitrogen, phosphorus, or potassium, are taken up by the plant, leading to an accumulation of salts in the soil. These salts can cause damage to the plant's cells, resulting in browning or scorching of the leaf edges. Additionally, the stress from nutrient overload can lead to leaf drop as the plant attempts to conserve resources and cope with the detrimental effects of the excess fertilizer. In contrast, stunted growth with dark green leaves may indicate other issues, such as nutrient deficiencies or poor light conditions. Rapid growth of stems but small leaves might suggest imbalanced nutrient uptake or environmental stressors, while flowering at inappropriate times could be related to factors such as temperature changes, photoperiod, or overall plant health rather than direct over-fertilization. Each of these scenarios highlights different aspects of plant health and care, but burnt leaf edges and leaf drop are specifically tied to the consequences of excessive fertilization.