Digging a square hole and mulching to prevent girdling

Tue. Jun. 18, 2019

Click below to listen to my 2 min. Garden Bite radio show:  Digging a square hole and mulching to prevent girdling

Mulching helps newly planted trees create stable root growth, which means longevity. I’ve told you this multiple times but I’ll say it again, when you mulch, think DONUT, not Volcano.


The idea is to mulch out to the dripline of the tree, away from the trunk. The point is that the roots will follow the mulch, so if you mulch at the trunk, there’s more chance of girdled roots.

Now I did just hear from a forester that they’re now advocating digging a square hole, not a round hole.

square hole from The Loop Newspaper

Something I’d never heard of and yet, when I googled it, there are some advocates. The idea is to, again, prevent girdled roots. Here’s what they’re saying, as you dig the hole, the sides of that hole become smooth and it’s more difficult for roots to dig into those walls but if the walls are square, there are cracks in the corner for the roots.

As I’ve advocated for years, dig your hole a minimum of twice as wide (bigger is better but NOT deeper!)  – using a mallet take a pole and tap holes into the sides of your hole about 4 inches down and about 6 inches apart, especially if you have compacted soil.  The roots will find the easier way to stretch out into the soil. 


I will always recommend loosening up those roots and being brutal in pruning them to make sure they’re not girdled when you plant that tree.

As for mulch, it really is important to get that mulch out away from the trunk. Spread about 3 to 4 inches of mulch around the tree out to the dripline or about 4 to 5 ft.. Continue to add mulch every 2 or 3 years as it breaks down.

A great article from the Morton Arboretum that includes types of mulches, all the advantages and possible disadvantages (such as TOO much mulch).