Gardening in Clay Soil: Choosing Plants

I have a friend who moved outside Atlanta, Georgia, a few years ago. She immediately started calling me about the soil with which she had she was dealing in regard to her penchant for gardening. It was clay. I told her to amend the soil with lots of organic material. For some reason, she could not do that. I told her that she could build raised beds. Apparently that was not financially feasible at the time. The only other recourse is to learn how to garden in clay. It can be done.

Clay is actually quite good for your plants. It holds on to the nutrients, retains moisture, and is actually an important element in good soil. It can be great, therefore, for your plants -- as long as it is not in large quantities. Trying to plant in soil that is nothing but clay can be a real chore. If it is too wet, it seems that you are just smearing around a slimy mess and not really getting a good planting hole dug. (You are not, as it turns out. The bottom that is collecting all of the wet clay will create a barrier through which plant roots can not grow.) If the clay is too dry, you might think that you need a sledge hammer to break through the surface. (I seriously doubt that even a sledge hammer would do the trick. Dynamite, maybe.) You really need to determine the best time for trying to plant anything in your clay soil.

Yes, you can plant stuff -- that will live and thrive, I should probably add -- in clay. There are actually numerous plants that do quite well in clay. You will need to determine the acidity or alkalinity of your clay soil, though, before choosing plants. Usually you can determine this by the vegetation growing around the area in which you want to plant. For instance, if you have a lot of pine trees growing close by, the soil is probably acid. If you are unable to determine the pH of your soil, you can do a soil test. I would also recommend that you not try to change the pH to suit the plants you choose. Clay holds on to its pH and is extremely difficult to change. (This, by the way, is more apt to kill your plants than the density of the clay itself.) You will do better to choose plants that suit the soil rather than trying to adapt your soil to the plants. Following are some plants that will actually grow well in clay soil:

Goat's beard (Aruncus dioicus): This hardy perennial grows to 5 feet and produces large, creamy-white plumes of flowers in the summer on sturdy stems covered with light-green, deeply-veined leaves. (Male plants, by the way, produce the best blooms.) The female plants will feature chestnut-brown seed heads in the fall. Prefers full sun.

Coral barberry (Berberis x stenophylla): Personally, I think that barberries can grow anywhere anytime. I have one growing in some really terrible soil in front of my house. (I never got around to creating a raised bed in that area; however, the barberry does not seem to mind a bit.) This hardy hybrid evergreen shrub can grow to be 8-feet-tall. In the late spring, it produces small, orange-yellow flowers followed by small, blue berries. Plant in sun or partial shade. Also, be sure to watch out for the spines growing along the stems.

Trumpet vine (Campsis radicans): If you want to attract hummingbirds to your garden, plant this fast-growing vine in full sun and give it something on which it can climb; e.g., a fence, trellis, or pergola. Large trumpet-shaped blooms appear in the summer and are usually red-orange in color; although, there are solid red and solid yellow varieties.

Spiderwort (Tradescantia): One of my and my husband's favorite flowers, the spiderwort is a constant bloomer throughout the summer, producing lovely three-petal purple flowers on sturdy stems with dull-green, strap-like leaves. Plant in partial shade.

Other plants to consider planting in clay soil:
Japanese quince (Chaenomeles japonica)
Daylily (Hemerocallis)
Hosta
Everlasting pea (Lathyrus gradiflorus)
Roses

References:

McHoy, Peter; Susan Berry; Steve Bradley. The Complete Book of Practical Gardening. London, England: Hermes House, 1998.

Tiny Treasures Nursery. Rare Plants from Rare Places. Berberis x stenophylla 'Corillina Compacta.'