Wild About Texas – October, 2007

Alpine plants are what come to most people’s minds when they think of rock gardens. Much of Texas is blessed with natural stone – sandstone in East Texas, limestone in much of the state, but particularly the Hill Country, igneous regions in the western part of the state and the mineral region of the Llano Uplift. These areas support alpine-like native plants, which are typically small, compact, mounding, clumping, trailing, and mat-forming.

The bane of most gardeners, thin soils can be advantageous to the rock gardener. This is good news for most of us in Texas with these kinds of soils. Those who have conditions that aren’t quite as appropriate can create them fairly easily. The ideal soil for alpine plants will drain well and not be too compacted. Create free-draining soils by building your garden on a slope or as a raised bed and by adding gravel or course sand (limestone sand works well in limestone areas and crushed granite is ideal for igneous-loving plants). Whether you have clay-, loam- or sand-based soils, some amount of compost is important. Compost from kitchen scraps is better than rich manure composts – you’ll get the soil-loosening benefits of organic matter without it being too “hot.”

Native plants that are adapted to starker conditions may become floppy or leggy in rich or overly watered rock gardens. Too much pampering may result in fungal problems, often resulting in the death of the plant. And neighboring plants may become overgrown, crowding out your cute rock garden species. Use a mineral mulch, such as gravel or crushed glass to allow moisture to wick away from the crowns of the plants, while keeping roots cool and reducing evaporation of moisture from the soil. Mineral mulches give a nice finished look with a pleasing character reflecting your taste.

Rock gardens are ideal for urban lots or for those with limited space. Even minor elevation changes from berms and terraces can help small spaces feel larger by adding depth in three dimensions. Smaller plants make it easier to build a collection and appreciate the details of your design.

Check your local library, bookstore, or the Internet to find out more details on how to construct and design your rock garden. Below are some good native options to incorporate:

Basketgrass (Nolina texana)
Black dalea (Dalea frutescens)
Four nerve daisy (Tetraneuris linearis)
Gayfeather (Liatris spp.)
Gregg’s dalea (Dalea greggii)
Grey golden aster (Heterotheca canescens)
Mexican feathergrass (Nassella tenuissima)
Nipple cactus (Mammillaria heyderi)
Prairie fleabane (Erigeron modestus)
Priarie verbena (Glandularia bipinnatifida)
Rainlily (Cooperia pedunculata, C. drummondii)
Shaggy purslane (Portulaca pilosa)
Strawberry cactus (Echinocereus triglochidiatus)
Thryallis (Galphimia angustifolia)
Winecup (Callirhoe involucrata, C. pedata)
Wright’s skullcap (Scutellaria wrightii)

Having a hard time finding native Texas plants? Many of these and others will be available at our Fall Gardening Festival and Plant Sale, Oct. 14-15.

For more information about Texas native plants and our Fall Gardening Festival and Plant Sale, visit the Wildflower Center’s website at: www.wildflower.org.

About the author: Andrea DeLong-Amaya is the Director of Horticulture at the Lady Bird Johnson Wildflower Center in Austin.

Posted by Neil Sperry
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