Root and soil care - before you buy another year of feeding

What is tree root & soil care?

Root and soil care is the work done below grade to fix a tree’s growing conditions: excavating a buried root flare, finding and correcting girdling roots, relieving compacted soil, correcting drainage, adjusting mulch, and - where a test shows a genuine deficiency - amending or fertilising. The order matters. Nutrients are rarely the limiting factor in a landscape soil; oxygen and root space usually are, and adding fertiliser to a compacted, oxygen-starved root zone changes very little.

Signs you need tree root & soil care

• The trunk goes into the ground like a telephone pole, with no visible widening at the base
• Mulch is mounded up against the bark in a cone rather than spread flat and pulled back
• Growth has slowed markedly, with short annual shoot extension and smaller leaves than the tree used to produce
• Vehicles, equipment or foot traffic regularly cross the root zone, or it has been used as a construction storage area
• Water sits on the surface over the root area after rain, or the ground is bone hard and sheds water instead of taking it
• A visible root crosses over the base of the trunk and appears to be pressing into it
• The lawn under the canopy has been repeatedly top-dressed or the grade has been raised over the roots

Seeing something not on this list? Browse tree service problems by symptom →

How tree root & soil care actually works

1. 1

   Excavate the root collar and find out what is actually down there

   Soil is carefully removed from around the trunk base - often with compressed air or water so roots are not damaged - until the flare and the top structural roots are visible. This is diagnosis, and it frequently ends the investigation on its own.

   Watch forA mechanical shovel used near the trunk. Severed structural roots at the base cost the tree far more than the buried flare was.

2. 2

   Deal with girdling roots

   Roots circling and pressing against the trunk restrict the tissue that moves water and sugars. Where one is found, the decision is whether to cut it, and that depends on its size, how much of the trunk it wraps and what the tree can afford to lose.

   Watch forA large girdling root cut out in one go without weighing the consequences. Removing a major root is itself an injury, and sometimes staged correction over seasons is the better answer.

3. 3

   Assess the soil properly, with a test

   A soil test gives pH, organic matter and nutrient levels. Compaction and drainage are assessed physically. Together these tell you whether anything actually needs adding, and to what depth the problem extends.

   Watch forA fertiliser programme quoted with no soil test behind it. Applying nutrients that are already present does not help the tree, and in some cases excess nitrogen produces soft, weak growth that is worse.

4. 4

   Relieve compaction and restore soil structure

   Compacted soil is loosened with air tools in radial patterns or in vertical holes, often backfilled with compost or a suitable amendment, so that oxygen and water can move into the root zone again.

   Watch forDecompaction sold as a one-off cure on a root zone that continues to be driven or parked on. Unless the traffic stops, the soil will be as tight as it was within a few seasons.

5. 5

   Mulch, correctly, and then leave it alone

   A wide, shallow layer of coarse organic mulch over as much of the root zone as the landscape allows, held clear of the trunk, does more for most trees than any product applied to them.

   Watch forThe mulch volcano - material piled against the bark. It keeps the trunk base permanently damp, rots the bark, and encourages roots to grow into the mulch and around the trunk, creating the girdling problem you were trying to solve.

What does tree root & soil care cost?

A root collar excavation on a single tree typically runs a few hundred dollars; soil tests are inexpensive; decompaction across a large root zone costs more and scales with area. Fertilisation is usually the cheapest item on the list and, without a test showing a deficiency, frequently the least useful.

See the full tree root & soil care cost guide - by material, size and region →

If the number is the problem, here are the ways people pay for it →