Mint grows as a hardy perennial in most climate zones. The plants spread profusely during the summer, so it's best to plant them in a sunken pot or confined garden bed. Mint doesn't require a high amount of fertilizer if you plant it in rich, well-drained soil. Too much fertilizer can prevent the plant from producing the oils that make the leaves flavorful. A once yearly application, beginning when you originally plant the mint and reapplied each spring, provides enough nutrients for the mint to remain healthy.
Things You'll Need
Spread 2 inches of composted manure over the planting site before planting new mint plants. Compost provides nutrients and improves the drainage of the bed.
Sprinkle ½ tsp. of a slow-release 16-16-8 fertilizer over each square foot of mint bed before you plant. Turn the fertilizer and compost into the top 6 inches of the bed. Plant the mint after adding the compost and fertilizer.
Fertilize existing mint once yearly in spring as the plant begins putting on new growth. Sprinkle 1 tsp. of 16-16-16-blend fertilizer around each plant, but avoid applying the fertilizer directly to the stems or leaves.
Irrigate the mint immediately following fertilization. Water dilutes the fertilizer, and so the plants are better able to absorb the nutrients.
Over-fertilization can result in rust and fungus problems on mint, in addition to diminished flavor.