Tough problem, pretty solution

Garden: A variety of plants can stand up to the challenge of Maryland's hard clay soil.

August 29, 1999|By Ary Bruno | Ary Bruno,Special to the Sun

The drought has taught many gardeners at least one thing: The hassles of working with clay soil. Rather than despairing, though, there is a fairly painless way to improve the problem -- clay-busting plants.

If you're still in doubt about what kind of soil you have, here are some diagnostic clues:

* Has your garden soil turned into a brick with the lack of rain? We're talking about that cracked, solid surface in which wilting tomatoes and marigold seedlings are held so tightly they seem cemented in. (This isn't to be confused with the dry crust that forms over good dirt.)

* Does the water seem to roll off the surface, even if you water regularly?

* Does damp soil feel smooth and sticky between your fingers instead of granular or rough?

You probably have clay soil. You also have a lot of company.

Clay soil is predominant in many parts of Maryland, says Elissa Levine, soils scientist at NASA in Greenbelt. She blames erosion, deforestation and urbanization, which she says have stripped off much of the topsoil and left the heavier clay behind.

This is frequently the bane of area gardeners. Even when well-dug or tilled, clay soil settles back into a sullen, cohesive mass that resists plant roots and often forms a bottom "pan" just below the cultivated layer that water cannot penetrate. It may even be holding a fair amount of water but because of its structure much of the moisture doesn't reach the plant roots.

Good, loamy soil is loose and crumbly because it contains equal amounts of sand, silt and clay. This allows water and air to easily pass through.

Clay particles, on the other hand, are small and more like flat plates. They tend to compact against each other tightly, making it difficult for air, water and roots to get between them. This makes clay a wonderful raw material for adobe bricks, but not for the garden or lawn.

The solution lies in picking plants that have strong, deep root systems. Those roots essentially do much of the digging for you. These clay-busting plants can be blended into almost any landscape plan.

As a bonus, most clay-busting plants are highly drought resistant. Many continue blooming while annuals and more delicate flora are turning to dust. This is because of their exceptional root systems, and their ability to go dormant during a prolonged dry spell.

Like horticultural miracle workers, their roots infiltrate the soil (up to 30 inches deep), open paths for water, air and earthworms to penetrate, bring up minerals and nutrients from within the ground and contribute organic matter as they decompose, enriching the soil.

What are some of these wonder plants?

As might be expected, many are native perennial plants and wildflowers that have been successfully busting clay on this continent for thousands of years.

Jennifer Baker, consulting ecologist and soil analyst with Prairie Nursery in Westfield, Wis., works daily with clients from around the country formulating custom seed mixes, many for battling clay soil.

"One of the best things about clay-busting plants is their ability to thrive on substandard soils, even the subsoil which is all that many new construction sites have to work with," she says.

"Such sites can actually be beneficial because their relative infertility decreases weed competition yet provides a mineral-rich environment which favors the native plants."

Several plants she especially recommends are White False Indigo (Baptista leucantha) in spring; Purple Coneflower (Echinacea purpurea), Pale Coneflower (E. pallida) and black-eyed Susan (Rudbeckia hirta) for late summer; and New England Aster (Aster novae-angliae), Ohio Goldenrod (Solidago ohioensis) and Stiff Goldenrod (S. rigida) for autumn.

Deep-rooted ornamental grasses also can supply grace and beauty year-round while working for you. Some of those suitable to our area include: Big Bluestem (Andropogon gerardii), Side oats gramma (Bouteloua curtipendula) and Switch grass (Panicum virgatum).

If a strictly wildflower or meadow planting doesn't suit you, remember that any of these can be interspersed beautifully in traditional flower borders. Many are indeed popular garden flowers in their own right here and abroad.

If you are interested in supplementing lawn grasses, Dutch white clover is a short-lived perennial long favored by the folks at Organic Gardening.

Cheryl Long at Organic Gardening also suggests perennial clover (Trifolium fragiferum), Strawberry Salinas, and sweet white clover (Melilotus alba) which has roots that can reach a staggering 25 feet.

Clay busters

Ornamental grasses

Big Bluestem (Andropogon gerardii)

Side oats gramma (Bouteloua curtipendula)

Switch grass (Panicum virgatum)

Indian grass (Sorghastrum nutans)


Butterflyweed (Asclepias tuberosa)

White False Indigo (Baptisia leucantha)

Tall Coreopsis (Coreopsis tripteris)

Purple Coneflower (Echinacea purpurea)

Pale Coneflower (E. pallida)

black-eyed Susan (Rudbeckia hirta)

New England Aster (Aster novae-angliae)

Ohio Goldenrod (Solidago ohioensis)

Stiff Goldenrod (S. rigida)

Dense Blazingstar (Liatris spicata)

Bergamot (Monarda fistulosa)

Smooth Penstemon (Penstemon digitalis)

Purple Prairie Clover (Petalostemum purpureum)

Yellow coneflower (Ratibida pinnata)


Prairie Nursery

P.O. Box 306

Westfield, Wis. 53964


Garland's Gardens

1109 Ingleside Ave.

Catonsville, Md. 21228


Carroll Gardens

444 E. Main St.

Westminster, Md. 21157


Niche Gardens

1111 Dawson Road

Chapell Hill, N.C. 27516


(for clover and other clay-busting cover crops)

Peaceful Valley Farm Supply

P.O. Box 2209

Grass Valley, Calif. 95945


Snow Pond Farm Supply

RR 2 Box 1009

Belgrade, Maine 04917


Pub Date: 08/29/99

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