How To Work With Clay Soils

Clay soils have their attributes — they can hold huge amounts of plant nutrients and they hold onto water really well.

When you walk about your yard on a wet day, do your shoes stick in the mud? Could you make ceramic pots out of the soil in your garden? Odds are you have clay soil, one of the biggest challenges to the home gardener.

Finely textured clay soils are difficult to work up and develop into a good seedbed. If the clay is dry, it tends to be very hard and lumpy. If it is wet, it tends to be very sticky and difficult to manipulate. It seems like a gardener's nightmare.

How To Amend Clay Soils

  Add Organic Matter

While it is impossible to alter the texture of a soil, you can increase the soil organic matter, which in turn will change the structure of soil. In gardening, having soil organic matter make up 4-6% of your soil profile is a great goal to strive for; this can be achieved by incorporating compost, green manure, animal manure, and leaf litter.

  Avoid Soil Compaction

Soil compaction occurs when soil particles are pressed together, reducing pore space between them. Heavily compacted soils contain few large pores, less total pore volume and, consequently, a greater density.

A compacted soil has a reduced rate of both water infiltration and drainage. This happens because large pores more effectively move water downward through the soil than smaller pores.

The first precaution you will need to take is to baby your clay soil. Clay soil is particularly susceptible to compaction. Compaction will lead to poor drainage and the dreaded clods that gum up tillers and make working clay soil such a pain. In order to avoid compacting the soil, never work the soil while it is wet. As a matter of fact, until your clay soil is corrected, avoid overworking your soil with excessive tilling. Try to avoid walking on the soil whenever possible.

Improving soil structure is the best defense against soil compaction. A well-structured soil holds and conducts the water, nutrients and air necessary for healthy plant root activity.

Read more: Improve Soil Structure

  Mulch

Mulch provides a number of vital services, including maintaining soil temperatures, reducing soil compaction, increasing organic matter, conserving water, and reducing weed pressure. Using mulch helps to maintain the soil structure and supports a diverse ecosystem for micro and macro organisms through the breakdown of mulch over time and the creation of habitat for these organisms. Common mulch materials are bark, straw, compost, grass clippings, leaves, pine needles, or wood chips.

Read more: Mulch Basics

  Cover Crop

Implementing cover cropping into your garden system can improve soil structure, increase organic matter, increase soil aeration, and aid in nutrient cycling. This is especially true if you are experiencing compact clay soils. Planting a cover crop is an effective way to reduce soil erosion by having plants “hold” soil in place via root structure and by holding moisture and slowing water filtration through the soil profile. After the cover cropping cycle is complete, a cover crop can act as a form of green manure when the cover crop is turned over and incorporated into the soil.

  Select Plants That Prefer Clay Soil

Select plants that have a better chance of thriving within clay soil. Great vegetables that don't mind having excess moisture include broccoli, cabbage, cauliflower, beans, and peas. Flowers that do well in clay soils include Aster, Purple Coneflower, Geranium, Heliopsis, Sage, Black-eyed Susan, and Skullcap.

Clay Soil Plant Catalog

The table below has 26 plants that are tolerant of clay soils. The list includes both full sun and shade tolerant plants, flowers, grasses, ferns and sedges. This is only a partial list but includes plants that are commonly found at your local native plant nursery.

Bloom	Common Name	Scientific Name	Color	Height	Light	Soil	Moisture
EARLY	Brome-Like Sedge	Carex bromoides	Green	1-2'		C,L	O,W
	Creek Sedge	Carex amphibola	Green	1-2'		C,L	M,O,W
	Pussy Willow	Salix discolor	White	10-20'		L,S,C	O,W
	Trillium	Trillium grandiflorum	White,Pink	1-2'		C,L,S	D,M
	Virginia Bluebells	Mertensia virginica	Blue,Lavender	3'		C,L,S	M,O
	White Dolls Eyes	Actaea alba	White	1-2'		L,C,S	M
	Canadian Wild Ginger	Asarum canadense	Red	3-5"		C,L	O
MID	Blue False Indigo	Baptisia australis	Blue	3-5'		C,L,S	D,M
	Wild Blue Phlox	Phlox divaricata	Blue	1-2'		C,L,S	M,O
	Pale Purple Coneflower	Echinacea pallida	Purple	3-5'		C,L,S	D,M
	Wild Iris	Iris shrevei	Blue	2-3'		C,L,S	W
MID-LATE	Black Cohosh	Actaea racemosa	White	4-6'		C,L,S	M,O
	Black-Eyed Susan	Rudbeckia hirta	Yellow	1-3'		C,L,S	D,M,O
	Butterflyweed	Asclepias tuberosa	Orange	2-3'		C,L	D,M
	Canada Wild Rye	Elymus canadensis	Straw	4-5'		C,L,S	D,M,O
	Common Milkweed	Asclepias syriaca	Pink,Lavender	2-4'		C,L,S	D,M
	Lady Fern	Athyrium filix-femina	Non-flowering	1-3'		C,L	D,M,O
	Prairie Blazing Star	Liatris pycnostachya	Purple	3-5'		C,L,S	M,O
	Purple Prairie Clover	Dalea purpurea	Purple	1-2'		C,L,S	D,M
	Rattlesnake Master	Eryngium yucciforium	White	4'		C,L,S	D,M
	Red Baneberry	Actaea rubra	White	1-2'		C,L,S	M,O
	Scarlet Beebalm	Monarda didyma	Red	3-5'		C,L.S	M,O
LATE	Joe Pye Weed	Eupatorium purpureum	Pink	4-6'		C,L,S	M
	New England Aster	Symphyotrichum novae-angliae	Purple	6'		C,L,S	M,O
	Showy Sunflower	Helianthus laetiflorus	Purple	6'		C,L,S	D,M
	Stiff Goldenrod	Solidago rigida	Yellow	3-5'		C,L,S	D,M

SOIL:  L = Loam      C = Clay      S = Sandy      R = Rocky
MOISTURE:  D = Dry      M = Medium      O = Moist      W = Wet