Tree & Shrub Food

Either inorganic or organic fertilizer is sufficient for a tree's needs.

Trees and shrubs in a well-landscaped yard help screen private areas, provide windbreaks and shade, and give the home a finished look. Trees and shrubs need the proper nutrients to grow strong and sturdy. Often, the necessary food is lacking in the soil.

NPK

Nitrogen, phosphorous and potassium are the three most important elements necessary to tree and shrub growth. If these are not available in the surrounding soil in sufficient quantities, the plants will do poorly. Nitrogen provides energy to the trees and shrubs while phosphorous assists in root, flower and fruit growth. Potassium's role is less understood but still vital. Collectively, these three elements are known as NPK.

Balanced Fertilizer

A balanced fertilizer needs more than NPK, though. Other secondary elements such as calcium and magnesium, and trace elements such as iron, copper and zinc are important. Purchasing a fertilizer with primary, secondary and trace elements is more expensive but better for the plant's health in the long run. Natural fertilizers such as compost contain less of the primary elements, but almost always include adequate amounts of secondary and traces ones.

Timing and Amount

Over feeding a tree, or feeding it at the wrong time, is as bad as not giving it adequate food. Home and garden stores sell easy-to-use tests that show the balance of NPK in the soil. If you over-fertilize the plants, you may create a runoff where the excessive fertilizer enters the water table, polluting the water for everyone else's use. Feeding at the wrong time interferes with the natural growth cycle of plants. October or April is usually best in temperate climates.

Methods

If the trees and shrubs are showing slow growth even with the proper watering, yellow leaf color in mid-summer, or are losing their leaves early, they may need fertilizer. Methods for feeding trees and shrubs include just sprinkling the food on the ground, driving specially made fertilizer spikes into the ground, or digging holes and putting the fertilizer near the roots. Some homeowners purchase equipment that pumps liquid fertilizer directly to the root system.

References

• University of Vermont: Trees Need Feeding; Dr. Leonard Perry
• North Carolina State University: A Gardener's Guide to Fertilizing Trees and Shrubs; Erv Evans; 2000
• University of Minnesota: Tree Fertilization: A Guide for Fertilizing New and Established Trees in the Landscape; Jeff Gilman; 2000