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Deep-Root Fertilization

Trees and shrubs need a balanced nutrient mix for proper growth and survival. In a natural setting, trees are fed by humus on the forest floor. In our urban environment, fertilizer is needed to take the place of this natural food. Our landscape also adds stress on trees and shrubs, like compacted soils, air pollution, road salts, poor drainage, and competition with turf grasses, which can impair the health and growth of the tree. Without realizing it, stressed trees are becoming more susceptible to insects and disease, further compounding the restricted grow. With that in mind, one of the best ways we can help our landscape plants grow healthier and to make it more resistant to pest infestation is to give them a proper supply of nutrients. Injecting a water and fertilizer mixture under high pressure 8 to 10 inches below the soil surface right where the feeder roots are in a grid pattern in and around the tree's drip line forces the water fertilizer mix throughout the root zone, which feeds all the roots and reduces soil compaction and adds root zone aeration. Depending on your plant varieties and their health, deep root injection fertilizer may be suggested throughout the year.
driplinePrimary tree roots grow down in the soil to anchor the tree. Secondary roots branch off and extend radially and horizontally and form the basis of the moisture and nutrient gathering system for the tree. Tertiary roots are the absorbing roots that branch off into clusters of rootlets. It is these roots, in conjunction with natural mycorrhizial fungi in the soil that break down the nutrients found in the soil, and transport them into the tree.

While the primary and secondary roots can be found rather deep in the soil, the tertiary and feeder roots will be relatively close to the soil surface. These roots will grow horizontally, to just beyond the outer drip line of the crown or foliage. This is where we must concentrate applying fertilizer for the trees to benefit the most.
These applications are usually timed for late fall and/or early spring. It's important to remember that tree roots remain active year round and the tree will benefit from these fertilizations even though the tree may look dormant.

Fertilizers are placed where the tree can get them, and it's important not to place them too shallow or deep, as most tree roots are 12" to 18" below the soil surface. Tree size and fertilizer analysis will dictate the actual amount of fertilizer we apply. To prevent groundwater contamination we don't apply quick release fertilizers when roots aren't active.

Tree care companies have special equipment that deliver fertilizer to the tree’s root zone, below your lawn’s root zone. In forests, trees shade out grass and other plants so the trees don’t have to compete with other plants. In your lawn, trees must compete with grass roots for nutrients. When you drop fertilizer on top of your lawn, the grass receives most of the benefits. A different type and method of fertilization is used to fertilize trees than what is used to fertilize lawns. For trees, slow release fertilizer is applied directly to the tree roots, just below the grass roots with special liquid fertilizers injected into the soil or dry fertilizers poured into holes drilled into the root zone. Over-fertilization can create tree health problems, so the need for fertilization should be determined by measuring annual growth, checking visual symptoms or chemically analyzing the leaves. Tree fertilization should be done according to ANSI A300 Part 2 standards for tree fertilization. A300 is the tree care industry’s standards for tree maintenance. A part of what A300 says about fertilizing trees:

1. A soil or foliage analysis should be done determine what nutrients are missing
2. Slow-release fertilizer is preferred
3. Fertilizer ratio should be 3:1:1 or 3:1:2, or adjusted for local conditions
4. 2 to 4 pounds of nitrogen should be applied per 1000 square feet
5. Sub-surface fertilization is preferred when lawn grass is present
6. The fertilization area must be known before fertilizing
7. Fertilizer holes or injection sites must be evenly spaced in the fertilization area
8. Fertilizer must be evenly distributed in the holes or injection sites

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