I am planning the conversion of our backyard, about 4000 sq ft of largely St Augustine, into a grassless landscape of hardscaping and native plants. I’ve been an avid gardener of rock garden plants in the east and in my new garden I want to grow small Xerophytic perennials and dwarf shrubs that can adapt to this dry and droughty environment of Austin.
The soil structure I have to work with is one of about 18” of clay over a limestone hard pan (caliche). It’s pretty clear that drainage is going to be an issue in growing the plants I want.
It occurred to me that a solution might be to build berms (sloping mounds or ridges without walls) to get the drainage I need. Raised beds are another possibility but berms appeal to me because they let water drain laterally and offer more planting area and microenvironments than a flat surface.
Building a berm of perhaps 20 feet by 10 feet with heights up to about three feet could be an expensive proposition, though. I’m reluctant to use construction fill to build up the base and save cost however because many rock garden plants have long taproots.
I am going to have a lot of St. Augustine sod to remove. Would it feasible to pile the sod up to build the base of a berm and then cover it with 12 inches or so of the gritty soil mix that the plants need followed by a pea gravel mulch. Variable size rocks and a boulder or two would be set into the berm to stop erosion and provide planting niches.
What do you think about the idea of using the reclaimed sod to build up the berms?
Have any gardeners in the region tried using berms to grow rock garden plants? Are there any garden designers or landscapers who have tried this?
Thanks in advance
David Guillet
