The Crevice Garden: How To Make The Perfect Home For Plants From Rocky Places

In May 2022, I visited the Denver Botanic Gardens. After I tore myself away from the array of tall bearded iris at the peak of bloom, I found nearby different renditions of the traditional rock garden. The rocks were not the smooth, roundish boulders but instead craggy slates, positioned vertically and close together, with only a limited cracks for the plants.

This was my introduction crevice gardening. This design expands the plant palette for gardeners in the dry, high altitude of the Rockies, but also in our own cool Mediterranean climate, by providing protection from wet winters that kill many plants.

It is appropriate that the new, and almost only, book on this topic – “The Crevice Garden” – has two authors that represent these climate extremes. Kenton Seth is from western Colorado. Paul Spriggs understands the needs of Seattle area gardeners from his crevice garden in Victoria, B.C. Both have careers as gardeners, and discovered their passion for alpine plants in part through backpacking and mountain climbing.

A crevice garden has more rocks than a traditional rock garden, covering at least half of the surface and typically raised to resemble an outcropping of rock. This keeps the plant tops and roots widely separated and in conditions they both prefer. The roots need the deep run with dependable moisture and even temperatures. The leaves and flowers stay dry and free of excessive moisture.

How do you do it? The design process is somewhat complex, but a detailed guide will take you through each step, from calculating how much of each material (rock, soil, dressing) to design and garden placement. And yes, planting! Some 250 plants are recommended, many new to me, but all sound intriguing. Most important is a location where you can watch your (often tiny) treasures from close by.

Several case studies display beautiful examples, including the garden at Far Reaches Farm in Port Townsend, Washington, appropriately titled “alpines in wet winters.” The authors appreciate that “gardening continues to be our most common connection to nature” and hope readers will embrace crevices to explore plants previously only available to keen specialists.

Reviewed by Brian Thompson for Garden Notes: Northwest Horticultural Society, Fall 2022

Alpine flora of the Canadian Rocky Mountains

In the late 19^th century in western Canada there were two women who had a lot in common. Mary Schäffer Warren (1861-1939) and Mary Vaux Walcott (1860-1940) were both of Quaker families living in Philadelphia, arguably the center for science and culture in America at the time. They both developed strong interests in the natural world, and developed the skills to paint in watercolors the native plants they found.

They joined a trip of the Philadelphia Academy of Natural Sciences to the Rockies and Selkirk Mountains of eastern British Columbia and western Alberta in 1889, traveling together part of the way on the top of a box car! They brought this same adventuresome passion to hiking and exploring the peaks, returning every summer for many years. Much of their stories are found in “A Delicate Art: Artists, Wildflowers and Native Plants of the West” by Mary-Beth Laviolette.

The pathways of the two Marys eventually diverged. Warren married her first husband, Charles Schäffer, whom she met in during one of these summer trips. He was an avid amateur botanist and together they continued their study of the local flora with the intent of publishing a field guide, using his text and her illustrations, both color paintings and black-and-white photographs.

Sadly, Charles Schäffer died before the book was completed, but his friend and fellow member of the Academy, botanist Stewardson Brown, completed the text. “Alpine Flora of the Canadian Rocky Mountains” was published in 1907. It profiles 163 plant species including trees, shrubs, and ferns, but the focus is on herbaceous wild flowers. The illustrations are lovely, but the book suffered by comparison to other popular field guides of the time by not quite satisfying either a professional or a general audience. The text is brief in its description of the flowers and foliage, and lacks the lyrical treatment of the guide published one year earlier by Julia Henshaw.

After that accomplishment, Warren became more of an explorer. Quoting author Laviolette, this “meant getting used to riding a horse, camping in all kinds of weather and travelling in the company of men who were neither family nor spouse.” She eventually moved to Banff, Alberta, married her second husband, guide Billy Warren, and is best known today for her mapping and discoveries in what is now Jasper and Banff National Parks.

Excerpted from the Winter 2022 issue of the Arboretum Bulletin

cascading plants for retaining walls

I’m looking to plant in a narrow strip on our retaining walls some “spiller” plants which will overhang the walls (which face north).

I’d prefer evergreen plants which would fill in fairly quickly,
but I could also mix in slower-growing and deciduous plants. There’s great drainage since I have gravel reservoirs
behind each wall, and the part of the plant above the wall will get part to
full sun, though I could overplant them if necessary for a plant that couldn’t
handle full sun.

I would like plants with interesting foliage and form to soften the look of the walls, and so would prefer a furry look to a spiny one. Flowers and fragrance are less
important though always nice, and I’m hoping to have at least 2 or 3 different
plant types with different colored foliage (shades of green are fine).

Some of the plants that occur to me, based on the description of your site, are
Brunnera macrophylla, Epimedium, Geranium phaeum, Stachys byzantina, Lamium
maculatum, and Liriope. Of these, the Geranium and Lamium will trail somewhat, while the others are essentially upright.

Graham Rice’s article on the Royal Horticultural Society site features a selection of recommended trailing (or spilling) plants. Here is another good list of trailing plants for walls.

You could also try entering your site requirements into the plant-finding and
plant selection web pages below:

Great Plant Picks (a local site)

King County’s native plant guide

Missouri Botanic Garden Plant Finder

Royal Horticultural Society Plant Finder

The Miller Library has many books on gardening in the shade, so you may wish to
come in and do some research to help you in your plant selection. Here is a booklist that may be of interest.

growing and caring for Silene

I am having trouble growing Silene (do not know the species). It has magenta flowers with notched petals on two foot stems and hairy basal foliage. I have killed four plants that were planted in four different locations. I am able to keep hundreds of other plants alive in my garden, but not this one! It flowers profusely from mid April through July. Then the leaves start wilting, and before long, it is dead. The only thing I can think of is that it needs superior drainage. Could I be overwatering it?

You may have one of the annual types of Silene, which die after setting seed. It is really hard to know for sure since there are over 500 species. You may be able to identify your Silene in the book Lychnis and Silene in the Garden, by J.L. Jones, 1999.

There are some magenta-colored species of Silene with notched petals (Silene dioica and Silene hookeri for example), as you describe. These are alpine or rock garden plants that prefer well-drained conditions and do not like highly acidic soil. It is certainly possible that you have overwatered or that the soil in which they are planted doesn’t drain sharply enough or is too acidic.

Rock Gardening: Reimagining A Classic Style

The Rock Gardening section of the Miller Library is quite extensive. It contains some of the library’s oldest tomes rich in detail, but the scarcity of newer titles might suggest this form of gardening has gone out of fashion.

However, for those interested in creating gardens that are tolerant of our droughty summers, rock gardening is an excellent style to consider. To help spur your interest, I recommend Rock Gardening: Reimagining a Classic Style.

Author Joseph Tychonievich has an infectious, enthusiastic writing style and easily brings new life to an old gardening subject. His research finds rock gardens evolving with expanding plant palettes. They are set in both sun and shade, and can be compatible with nearby, more lushly planted areas. Moreover, they don’t necessarily include rocks! “This book aims to be an introduction into that wide world of the rock garden in all its diverse modern incarnations.”

He uses many examples from throughout the United States and the United Kingdom, and includes two gardens in Medford, Oregon. His list of recommended plants is restrained but goes well beyond the traditional alpines, and encourages experimentation.

Published in Garden Notes: Northwest Horticultural Society, Fall 2017

Garden Tip #418

Alpine and rock garden plants are so cute with their pin-cushion growth habit and tiny, jewel-like flowers. The best way to try growing these specialty plants is in a container. Stone or hypertufa troughs are traditional, but any sturdy pot about 12″ deep with a hole in the bottom will do. The critical element for success is very well draining potting medium. Mix in plenty of pumice, perlite or gravel into bagged potting soil. Most alpine plants prefer full sun, but there are species for every light condition. Creating and Planting Garden Troughs by Rex Murfitt and Joyce Fingerut is a great book to get started with trough gardening.

Keyword: Alpine and rock gardening