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The most important parts of the tree are the roots you can’t see.

We know many chemicals are in soil but what happens to soil in a tree well? Are there ingredients we can add to make the soil better?

Project 1: Grow Better will find out what happens to soil in tree wells and how enhancements help. What is our method?

Subject: 55 Elm trees planted downtown in 2010

Step 1: Remove the old soil in the tree well

We used a hydro-vac machine to extract the soil into a truck using water.

Step 2: Plant tree and backfill with different treatments

All 55 elm trees were backfilled with fresh soil (#3 mix). Twelve trees received one of the components listed below with the soil.

  • Compost - used to add nutrients and improve soil structure
  • Horticultural Lime – used to neutralize de-icing salts and improve soil structure
  • BioChar – used to absorb and filter contaminants

Step 3: Test soil and check plant health

In the fall of 2010, we tested the soil around 16 trees (12 with treatments, 4 without). We repeated the soil testing, spring and fall, for the next three growing seasons (2011 to 2013). To monitor the health of the trees, each fall we measured their size (diameter at breast height).

For More Information


In Edmonton: 311

Outside Edmonton: 780-442-5311

Fax 780-496-4978

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