When a house plant has not been repotted or fertilized for many years, you might find signs of distress, such as leaf yellowing. Like all living things, plants require specific nutrients to reproduce, photosynthesize, and maintain homeostasis. Which nutrients do plants require to thrive?

Healthy plants need organic, carbon-based compounds as well as inorganic nutrients, commonly called minerals. 

There are about 17 nutrients that support all of a plant’s biochemical needs. These elements are called essential nutrients; no other elements can substitute for essential elements, and without them, a plant cannot complete its life cycle.

Among the essential nutrients are carbon, hydrogen, and oxygen, which are derived from the atmosphere and water. Most plants acquire all other essential nutrients from the soil in which they are rooted. 

The two groups of essential nutrients are macronutrients and micronutrients. Macronutrients include carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur. Plants require these elements in relatively large amounts. 

Carbon makes up about 45 percent of the dry mass of plants, and is a key component of proteins, nucleic acids, and carbohydrates. Nitrogen is likewise a critical constituent of nucleic acids, proteins, and the photosynthetic pigment chlorophyll. Potassium is vital for regulating gas exchange, a process critical for photosynthesis. 

Essential plant nutrients needed in smaller amounts are called micronutrients; the micronutrients chlorine, iron, manganese, boron, zinc, copper, nickel, and molybdenum are required for proper plant functioning. 

Some micronutrients function as cofactors, which are substances that help enzymes work properly. For example, iron is a cofactor for enzymes in the mitochondria and chloroplasts. 

If a plant is deficient in an essential nutrient, it begins to show symptoms like chlorosis or yellowing leaves. The particular nutrient deficiency can often be determined by examining the plant’s appearance and the soil nutrient content. 

Though essential nutrients account for a relatively small amount of a plant’s mass, they are crucial for plant growth and homeostasis.