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July 19, 2002, 7:13PM


This summer, outsmart slugs, snails


Special to the Chronicle

The lark's on the wing, The snail's on the thorn:

God's in his heaven --

All's right with the world.

If poet Robert Browning pictured a snail impaled on a thorn, he's of one mind with a lot of Houston-area gardeners.

People who recommend upturned grapefruit rinds and jar lids full of beer have never experienced a true Houston invasion.

Snails and slugs don't invade every garden. They don't eat every plant. Something in your yard is inviting them in.

Slugs and snails hide in dark, moist corners during the day and need soft, relatively smooth pathways to night dining spots.

Remove old boards, stacked pots, bricks or other material that make good hiding places. Thickly line inner sides of garden borders with fireplace ashes, cornmeal, crushed eggshells, cedar mulch or crushed coral rock (available where hydroponic gardening supplies or tropical fish are sold). Sprinkle on soil around infested plants. Lightly pack into the soil so the critters can't burrow underneath.

Mary Herr, an antique rose grower, swears by CedarCide, a cedar-based mulch with natural herbicidal properties. Diatomaceous earth (ground-up fossils) also works. But use these and other snail treatments cautiously, as they will kill some beneficials.

Birds eat snails and slugs, as do garden snakes and firefly larvae. Donald Burger, a Heights gardener, has a great section on fireflies at www.burger.com.

Replace attacked plants with unappetizing varieties -- or at least cut them back to remove temptation. Fill in bare areas with tough annuals.

A survey of area experts netted this list of untouched annuals:

In sun: cleome, cosmos, globe amaranth, jatropha, Florida flat leaf purslane, Mexican zinnia (Zinnia linearis). Part sun: periwinkles and torenia.

In shade: bromeliads, caladiums and coleus.

Don't waste energy on plants always attacked by snails and slugs. Replace with these perennials that, in most gardens, seem to be unappetizing (no guarantee, of course):

In hot sun: asclepias (butterfly weed), blood lily, hamelia, iris, lantana, Mexican mint marigold, rain lily, nandina and yellow bells (Tecoma stans, esperanza).

In part sun: blue daze, shrimp plant, rosemary, lemon grass, shrimp plant, summer phlox and turnera. Torenia is a good fill-in annual for instant color in part sun or shade.

In shade: Australian violet, sweet violet, coleus, firespike, four o'clocks, pigeonberry, ruellia (Mexican petunia), sensitive or royal fern and wedelia.

Chronicle garden editor Kathy Huber finds snails literally by the hundreds on a cloudy day. The pests have tattered Rudbeckia maxima, lanceleaf and `Indian Summer' rudbeckia, yet avoid `Goldsturm.' Snails have devoured pentas, and while they congregate on the flowers of indigofera, the pests ignore the foliage. The snails call thick clumps of society garlic home, but leave the pungent foliage intact, oddly enough directing their attention instead to the rough leaves of purple coneflowers. The snails like the flowers, too. Peacock gingers get a fair share of nibbles, hostas somewhat less.

Diversity in the garden is one key to controlling such invasions. The greater the variety, the more types of beneficial wildlife you will attract, and they will take care of most problems.

Address questions to Brenda Beust Smith, 9039 Katy Freeway, Suite 502, Houston, TX 77024 (e-mail: lazygarden@aol.com ).

mail comments to burger@burger.com

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