What does well in clay soil? - Knowledgebase Question

Blacksburg, So
Question by mmjweldon
June 24, 2008
Our garden area has mostly clay soil & is very rocky,we have spent the 2 or 3 years building up the soil with compost and have also added about 200lbs of lime. What can we do to improve both yield & soil? We are located in the Piedmont area of SC.Garden has a slight slope overall & our project for the winter will be to box it in then fill the box to level with a mixture of bags of potting soil & bags of topsoil. That will help next year but we need to improve yields for this year. Thank you for your time

Answer from NGA
June 24, 2008


Clay soil is one of the most difficult conditions a gardener can face. Dense and slippery when wet, it's even more of a challenge as it bakes brick solid when dry. Clay particles are extremely small and tend to pack together, leaving no room for air or water movement.

The first order of business here is to improve the texture of the soil with organic matter. This will be an ongoing process, but the benefits will pay off in the long run. Generously amending or top dressing with compost, leaf mold, composted manure or other organic matter will gradually bulk up the texture of your soil, lessening the compaction. The good news is that clay tends to be much higher in nutrients than a sandy soil.

Choosing plants to grow in clay soil takes some discretion. Certainly, plants that need a well drained soil are not going to be happy growing in clay. Don't give up. There are plants that not only tolerate clay soil, many will also help break up and improve its texture. Rugged native prairie plants have the constitution to hold up in clay. Tap rooted plants can get deep enough so that their roots don't rot and they break up the texture of clay on their way down. Some of those plants include the following:

Amsonia Blue Star (Zones 5-9); Asclepias tuberosa Butterfly Weed (Zones 4-9); Aster (various) Aster (Zones 4-8); Coreopsis Tickseed (Zones 4-8); Echinacea purpurea Coneflower (Zones 3-9); Eryngium yuccifolium Sea Holly (Zones 5-10); Helianthus angustifolius Swamp Sunflower (Zones 6-9); Helianthus x laetiflorus False Sunflower (Zones 5-9); Heliopsis helianthoides Ox Eye (Zones 4-9); Hemerocallis Daylily (Zones 3-10); Liatris pycnostachya Kansas Gayfeather (Zones 4-9); Liatris spicata Blazing Star, Gayfeather (Zones 4-9); Monarda fistulosa Wild Bee Balm (Zones 3-9); Ratibida pinnata Drooping Coneflower (Zones 3-10); Rudbeckia hirta Black-eyed Susan, Gloriosa Daisy (Zones 3-7); Sedum 'Autumn Joy' (Zones 3-10) ; Silphium integrifolium Prairie Dock (Zones 4-7); Silphium laciniatum Compass Plant (Zones 5-9); Silphium perfoliatum Cup Plant (Zones 5-9); Solidago Goldenrod (zones 5-9); Vernonia noveboracensis Ironweed (Zones 5-9); Yucca filamentosa Adam's Needle (Zones 5-10).
Ornamental Grasses Suited for Clay Soils:
Andropogon gerardi Big Bluestem (Zones 2-7); Elymus canadensis Canadian Wild Rye (Zones 3-8); Miscanthus sinensis Eulalia Grass (Zones 4-9); Panicum virgatum Switch Grass (Zones 5-9);Pennisetum (various) Fountain Grass (Zones 6-9); Sorghastrum nutans Indian Grass, Wood Grass (Zones 5-8); Spartina pectinata Prairie Cord Grass (Zones 4-7).

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