Anything But Groundcover; Gardening in Clay 
January 19, 2010
Allan in Gardening Tips & Advice, groundcover

Dianthus is a suitable substitue for groundcover. It flowers colorfully with an intoxicating fragrance. This image is courtesy of Panache Exterior Designs.

The first article that popped up in my Google Reader this morning was a blog posted by Elizabeth at Garden Rant.  In it, she writes about the difficulty growing flowering perennials in part to full shade, and the success she achieved when instead she planted ground cover, bulbs and spring flowering shade plants. My heart sank as I read this because groundcover does not satisfy me. I cannot imagine a garden without summer flowers and the colors they provide. However, I can understand Elizabeth’s frustrations. I faced a similar challenge once, with clay soil.

The first home that my wife and I purchased had a garden the size of a postage stamp. There was no earth worth cultivating. The back yard was a gardener’s worst nightmare. The earth consisted of heavy clay that turned to concrete in the heat of the summer sun. It was clear that nothing could grow there unless the soil was first transformed into arable land. Since that was a time in life when I though that I was invincible, I decided to amend the soil rather than build a flowerbed over it.

The first step was to roughly dig down into the clay until I reached a depth equivalent to the length of two spade-heads laid back to back. This initial digging created a lunar surface over which I spread a generous amount of garden sand. To help the sand infiltrate the clay, I turned the hose nozzle to jet, aimed it at the sand, and started spraying water. In a few minutes, the pressure of the water helped at least half of the sand find its way into the newly created fissures in the clay. Then I spread a generous layer of peat moss over the surface and the hard work began. Starting at one end of the garden, I tilled the earth in order to blend the peat moss into the sand-clay mixture. After that step was complete, I returned to the starting point of the garden and began tilling again, this time with the intention of blending all of the components in the soil until a loose granular loam resulted.

Too many years have past since then, I cannot remember how many times I needed to till until I created loam. All I remember is that it was worth the effort. I grew vegetables, annuals, and perennials with ease. The heat of the summer sun did not turn the earth into cement and the very heavy weight of the winter snow, sometimes two feet deep, could not compact the soil back into clay. Groundcover was never going to be an option for me and I never had to work the soil again for the 17 year that I gardened there.

That said, I notice that some landscape architects design gardens using mostly ground cover and foliage with little or no flowers. Gardens such as these may be beautiful and restful both to the eyes and the soul. However, for those of us that are propelled into gardening by flowers and their colors, gardens of groundcover and foliage remain less than satisfying.

There have been occasions when I have found some parts of my present garden more hospitable to weeds than to perennials. Instead of groundcover, I experimented with summer flowering perennials that are happy in sun, shade and both wet and dry clay. The results have been satisfying. The two families of perennials that have worked well have been the silver-leafed Dianthus for sunny locations and Geraniums for both sun and shade. I planted Dianthus in a hard, dry, clay rock garden and it spread slowly to densely cover a respectable patch of earth. To enhance its value as a ground cover substitute, I  recommend planting several Dianthus instead of one. Results, that are similar to using grouncover, were obtained with perennial Geraniums even though they are taller than most ground cover plants. The density of their foliage allows them to do the same weed prevention work. Geraniums grow more vigorously than Dianthus do, so planting one perennial alone is enough to create a large patch of groundcover within two years. Favorite Geranium varieties for this project are Rozanne and Patricia. Both flower for most of the summer with Rozanne remaining in bloom until the first snowfall.

Article originally appeared on Garden Design, Montreal, Perennial Flower Gardens, Gardening Tips, Gardening Advice, Gardening Book Reviews (
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