What causes plants to be leggy and weak-stemmed?

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

Answer: (D)

Leggy, weak-stemmed growth happens when light is insufficient, so the plant stretches toward the light to photosynthesize. In crowded settings, plants shade one another, reducing the light each plant receives. That shading triggers etiolation—stems elongate and become thin and fragile as the plant tries to reach for light. So crowding directly leads to leggy growth because it limits light availability per plant.

Overwatering stresses roots and can cause yellowing and wilting; underwatering dries out the plant and causes droopy foliage; cool temperatures slow growth and can cause overall stunting. But the specific long, wispy stems of leggy plants are best explained by reduced light from crowding.