What causes plants to be leggy and weak-stemmed?

• A. Over watering
• B. Under watering
• C. Cool temperatures
• D. Crowding

Answer: (D)

Leggy, weak stems happen when a plant doesn’t get enough usable light. When light is scarce, the plant grows longer internodes and stretches toward the light source in an attempt to capture more light. Crowding makes this worse because nearby plants shade each other, reducing light intensity and triggering that same stretching response. The result is taller, thinner, and less sturdy stems.

Other stresses like overwatering or underwatering affect roots and leaves and aren’t the primary cause of leggy growth. Cool temperatures can slow growth overall but don’t directly cause the characteristic elongation from insufficient light. So crowding best explains why the stems become leggy.