New Fruit Trees

• Before you plant a new fruit tree, you will need to prep the soil with fertilizer. The majority of new trees do best when you work a mix of phosphorus and potassium into the soil prior to planting the tree. You can obtain the phosphorus from a garden supply store or certain mass retailers, or use animal manure mixed with straw or compost. You can also purchase straight potassium, or you can work wood ash into the soil prior to planting.
  
  

Spring Fertilizing

• Existing fruit trees often do well with an application of fertilizer right before spring blooming. For most trees, a balanced fertilizer of 10-10-10 will supply the tree with all of the nutrients it needs to grow and bear fruit. According to Richard Jauron of the Iowa State Department of Horticulture, trees should receive 1/10 lb. of fertilizer for each year of age, starting from the point you planted them. For example, a two-year-old fruit tree will need 1/5 lb. of fertilizer in the beginning of spring, spread out 3 feet around the tree. After the tree is 10 years or older, it will only need a maximum of 1 lb. of 10-10-10 fertilizer spread 3 feet around the tree.
  
  

Fertilizing Based on Soil Tests

• While a balanced fertilizer works in many cases, the soil your tree is growing in may require a different mixture, depending on the soil's pH balance. You can purchase a soil testing kit from most major garden stores and test the soil around the base of your fruit tree. If the soil has a pH higher than 7.0, use a 21-0-0 fertilizer to balance out the nutrients. Soil that has a pH below 7.0 requires a 15-5-10 fertilizer for optimal fruit tree growth. Apply the fertilizer in the first part of spring, at a rate of 1/10 lb. per year of the tree 3 feet around the base, with no more than 1 lb. of fertilizer for trees more than 10 years old.
  
  

Fruit Trees Planted in Lawn Areas

• If you have fruit trees growing in your front lawn or backyard, you may not need to fertilize them at all if you use lawn fertilizer on your grass. The nutrients in lawn fertilizer typically provide all your trees need to grow and bear fruit. Using a lawn fertilizer on your grass and additional fertilizer for the fruit tree is likely to over-fertilize the tree, which can be detrimental to its growth and production of fruit.