Smart way to save on space and soil
Crevice gardens are a sustainable solution for ecoconscious gardeners
Ecologically minded, nativeplant gardens are both on trend and a relatively recent impulse.
But for the past century or more, gardeners have wanted to grow plants that were exotic and different, including nonnative versions of roses, azaleas, hostas and lilies.
Sometimes, the craving for exotica meant creating whole new growing environments — none more adventurous than the rock garden.
Now, there’s something even more adventurous than a rock garden: a crevice garden.
While a rock garden is formed from soil and grit and gravel piled between boulders, a crevice garden uses slabs of stone set vertically and close together. There is less expanse of growing space and virtually no soil.
Tony Avent has created a crevice garden at his Plant Delights Nursery, in Raleigh, N.C.’s Juniper Level Botanic Garden.
It is about 90 metres long, almost two metres high and made of broken concrete slabs.
Avent’s creation offers a model of urban sustainability.
“I think it’s a great way to green cities while keeping stuff out of the landfill and exposing people to a whole new palette of plants,” he said. “I hope this will be an inspiration to cities around the world.”
Where once a line of old holly trees stood in the botanic garden, the crevice garden has given Avent a whole new playground for his unusual plants — many of them arid-region plants including yuccas, agaves and prickly pears.
Some of his choices are found in more conventional garden settings and include species of dianthus, penstemon, germander and daphnes.
What these plants lack in soil, they gain in the elongation of their roots. A plant that might be eight inches high, huddled between two slabs, could have root strands reaching down several feet.
Their length increases the plant’s access to moisture and nutrients, often in a partnership with bacteria.
“A lot of plants are adapted to absorbing mineral nutrients rather than organic, humic nutrients,” said rock garden designer Kenton Seth, of Fruita, Colo. “They get their minerals straight from the rocks.”
In the first crevice garden sections, they used no soil but instead a horticultural-grade aggregate named PermaTill. Many of the plants — 588 hardy cactuses and agaves — did not make it through the winter. The high mortality rate was not due to wet soil from record levels of rainfall in 2018.
Instead, Avent and Schmidt discovered that the growing medium was too open, and frigid air was reaching deep into the ground.
They changed the growing mix to include compost and some native soil to fix the problem. Today, 1,500 plants thrive in the garden, including more agaves and hardy cactuses, delosperma, arabis and draba — all of which would probably not survive in normal garden beds in central North Carolina.
There is a pleasing tension seeing seemingly delicate, novel beauties such as globularia, with its chivelike blossoms, growing amid the hulking slabs.