Stem girdling roots on a nursery tree

Roots should grow more-or-less straight out from the trunk as shown above.

Roots on this tree grew to the edge of the container and were deflected up to the top of the media. Then they grew toward the trunk. This was caused by planting too deeply in the container and not cutting roots when tree was potted to the larger size. This root will restrict proper trunk development after it is planted into the landscape and can lead to tree instability. Soil line is shown on trunk as a red line.