New York City Gardener Practice Exam

Plants need nutrients in larger amounts, and the fertilizers are labeled to highlight the trio they rely on most: nitrogen, phosphorus, and potassium. These are the primary macronutrients because they are required in higher quantities by most plants to support fundamental growth processes. Nitrogen fuels leafy growth and chlorophyll production, phosphorus supports root development and energy transfer within the plant, and potassium helps overall vigor, water regulation, and disease resistance. That’s why including all three together is the best answer.

Calcium and magnesium are important too, but they’re considered secondary macronutrients, needed in moderate amounts rather than in the largest quantities. The other options either omit one of the primary trio or focus on a single nutrient, which doesn’t reflect the standard grouping used on fertilizer labels.