Sitting in a boulder field at the foot of St. Mary’s Glacier last summer, I had an epiphany concerning shade gardening.
The spruce and bristlecone pine woods just beyond the glacier’s edge are dotted with boulders. Understory shrubs and wildflowers nestle up against the boulders to take advantage of the extra protection and moisture their bulk affords.
So, why is it that you almost never see rocks and boulders in shade gardens? Perhaps it’s because our agricultural heritage inevitably spills over into and influences our horticultural practices.
The first thing most of us do when we build a garden is to level the entire bed as much as possible. Then we amend the soil to a uniform tilth, as if we were preparing the soil for a crop of vegetables.
Rocks and boulders have no place in such a garden. Traditionally, any stones found during the construction phase are removed and discarded.
But ornamental gardens, in shade or otherwise, are not fields for crops. Our collective sensibilities may be accustomed to such artifice, but little in nature conforms to this homogenous model. With this in mind I took a fresh look at the shade garden beneath trees on the west side of my home.
The walk through this area resembles a meandering stream bed. I was aiming for a naturalistic look, not an exact copy, but a reflection of the real thing. To achieve this I used three different sizes of river rock for the path, and pushed most of the large rocks to the sides, as if they had been deposited there by rushing water. Lastly, I set in three large boulders at uneven intervals along its length.
This dry streambed handles runoff from thunderstorms, its uneven surface trapping water and allowing it to permeate into nooks and crannies between the rocks. This provides extra water to the trees and stops the erosion that once occurred as water ran downhill on the other side of the property line.
In all respects, the dry stream-
bed is a success, but there was still a slight disconnect between this craggy, naturalistic feature and the level surfaces of the borders on either side.
Since last summer I’ve been gradually adding boulders. None are larger than the one- or two-man size that my husband, Randy, and I can wrestle into place with the help of an appliance dolly.
I’ve also attacked the other part of the equation – the level beds. Boulders do not appear to be natural, nor are they stable if they are simply plunked down on the ground.
Arranging them randomly, but in groups to suggest outcrops of rock just beneath the surface, I added soil around the base of each and sculpted the surrounding beds into slight hills and swales.
It’s important to ensure that the contours are not even. You don’t want them to resemble ancient burial sites.
While it’s too soon to measure what effect this will have on the plants in this border, I suspect that it will be positive. Depressions catch and hold water and boulders help protect plants from seasonal fluctuations. But, in any case, the dry streambed and the beds alongside now harmonize with one another.
Marcia Tatroe is author of the forthcoming “Cutting Edge Gardening in the Intermountain West,” due from Johnson Books this spring.
