Healthy Roots, Happy Tree

Your tree’s root system is its nutritional lifeline and the anchor for above-ground growth. So whether for preventing or treating injury, good tree care starts at the bottom.

underground tree roots

Deep Root Fertilization

If your tree is struggling—has yellowing or off-color leaves, new-shoot growth under six inches, or visible dieback—it could be a candidate for deep root fertilization.

This method allows arborists to deliver nutritional treatments—such as ArborKelp, our sea kelp-based biostimulant, and ArborHealth, our slow-release fertilizer—directly to your tree’s root system.

Through a preliminary soil test, your arborists can create a fertilizer blend to suit the needs of your soil. Then they’ll use specialized hydraulic equipment to inject the liquid fertilizer into the tree’s root zone about six to eight inches beneath the surface. They’ll continue the process, spacing injection sites two to three feet apart in a grid pattern underneath the tree’s canopy and slightly beyond. Deep root fertilization gets nutrients to your ailing tree fast, and has the added benefit of aerating the soil.


Proper mulching will suppress weeds, help soil retain moisture, insulate roots against extreme temperatures, and add nutrients to the soil as the mulch decomposes. But beware! Overmulching above a tree’s root ball causes the roots to grow up and into the mulch in search of water and air, causing a potentially deadly condition known as stem girdling.

So please, obey these two cardinal rules:

  • Apply only two to four inches of mulch to the tree bed
  • Keep mulch away from the tree’s trunk. Whether newly planted or long-established, the tree’s trunk flare should always be visible. Start the mulch 3 to 6 inches from the trunk (regardless of the tree’s size), lay down a two-inch layer of mulch, and gradually increase the depth to four inches as you move away from the trunk.

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