The lone voice of horticultural reason
“When planting a tree, dig a hole twice the diameter of the container.”
Since the 1800s, everything written about planting a tree tells you to do just that, of course, the old “forty-dollar hole for a twenty-dollar tree” myth. But university studies in the past few years tell us that your goal when planting a tree is to dig as wide a hole as possible, a five-hundred-dollar hole for a twenty-dollar tree.
Turns out that too often, roots from trees planted in a modest hole never break out beyond the hole to any healthy degree. Often, the roots circle around the hole, and hopefully don’t girdle the tree. Except they do, to some degree, meaning the tree never takes off, never becomes vibrantly healthy, and is prone to dying young, if not blowing over in a storm.
So dig your hole as wide as possible. I dig a hole about two or three times the diameter of the container (or width of the root ball, when planting balled-and-burlapped (B&B) plant material). Then I rototill out and around from there, busting up the soil as deeply as possible. How far? In a new landscape, if I can get the trees and shrubs in before the sod goes down, I’ll rototill as wide as twenty feet in diameter if the soil in the area is compacted.
In tight situations, or lousy soil, do what the Norwegians do: dig your hole as wide as possible, then dig four to six troughs out away from the hole, resembling the shape of a samurai star. Replace the loosened soil into the troughs, and years later, the tree’s roots will have extended away from the tree down the troughs.
The Renegade Gardener