Fertilizing 101: The Best Plant Foods

The three major plant foods are nitrogen, phosphorus and potassium. All plants need these to maintain good health.
Nitrogen Rich

Nitrogen Rich

Plants, like this hosta, need three major nutrients which are nitrogen, phosphorus, and potassium. All plants need these to maintain good health.

©2008, Dorling Kindersley Limited

2008, Dorling Kindersley Limited

Nutrients such as calcium, magnesium and sulfur, are required in smaller quantities, while tiny amounts of other nutrients are also vital but rarely deficient in garden soils. One exception is alkaline soil, which is unable to release manganese and iron, and causes yellow leaves on acid-loving plants. A general-purpose fertilizer has equal amounts of the major plant nutrients, together with other nutrients that are not always readily available in the soil. 

  • Nitrogen (N) encourages lush leafy growth, and is the main ingredient in spring lawn fertilizers. It is highly soluble and quickly washes out of free-draining soils. 
  • Potassium (K) promotes flowering and fruiting; it is sometimes listed as potash. Fertilizers for tomatoes and summer container plantings are rich in potassium. 
  • Phosphorus (P) promotes healthy root growth, and is essential for young plants whose roots are developing. There is usually plenty in garden soil in the form of phosphates.
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