By Elaine Rohse • Columnist • 

Rohse: Slow, yet surprising: Slugs both beneficial and harmful

On a lovely spring morning, gardeners all across the Yamhill Valley are eager to get outdoors to see how seedlings, planted the day before, fared through the night.

Many of those gardeners are apt to be heartsick at finding many of their plants chewed down to a leaf or two, with no chance of survival. And the gardener may recall a recent story suggesting a single garden plot could host hundreds if not thousands of slugs.

The good news is that there are some flowers that snails and slugs are NOT particularly attracted to: dahlias, zinnia, hosta, larkspur and sunflower. And some flowers are particularly resistant to mollusks: geranium phlox, aster, poppy, veronica, rose, dianthus, mint, hydrangea and succulents.

Slugs can live for about six years, but their eggs can lay “dormant” for years, then hatch when conditions are just right. Mollusks have up to 27,000 teeth, and their chewing capability determines in large measure the food they eat.

Ferns are not favored by mollusks because they are difficult to chew. Iris and day-lilies are sometimes spared for the same reason.

Some flowers have developed methods of becoming resistant to mollusk smell or taste through toxic ingredients, hard leathery leaves, stinging hairs and tough stems.

Slugs prefer weak plants — ones that are dying or just getting started. Mollusks have a keen sense of smell that alerts them to plants they probably won’t like, and those are usually left alone.

Mollusk can also be spelled “mollusc,” derived from its mollusca phylum classification, but mollusk is preferred.

Oregon is home to 124 species of terrestrial mollusks. They feed on what they find in farmlands, wetlands and woodlands. Their bodies need moisture and humidity, so they enjoy wet garden and jungle settlings.

Some mollusks are almost amphibian, while others survive in the deserts of Egypt and Israel.

Snails sometimes hitchhike in the plumage of birds, and that can have unfortunate results. The giant African snail has been introduced to many new parts of the world, and is now considered one of the most dangerous invasive species of all.

Willamette Valley farmers know the ravages of voracious mollusks well.

A 2012 study pegged annual mollusk damage to crops such as annual rye grass, perennial rye grass, fescues, orchard grass and clover at $60.8 million. Annual rye grass led the list with an annual loss of $24.5 million.

Recent reports estimate annual damage in the United Kingdom at 10 million pounds. British gardeners are said to use about 650 billion slug pellets a year.

Slugs and snails are well known for their lack of speed and rather unpleasant appearance, but are now receiving considerable attention in the medical field.

For centuries, ancient Greeks and Romans used snails to cure a variety of ailments. In the 18th century, snail application was a recommended treatment for anthrax, and in the 19th, for tuberculosis.

Recently research shows that some properties of mollusks enhance the human immune system. An abalone powder strengthens the body, enhances liver function, helps the heart, promotes sexual function and helps prevent anemia. These days, you may even find help from mollusks in your toothpaste.

Despite damage to crops, slugs and snails are important to our environment and health. They provide food for insects, earthworms and birds.

Thrush particularly depend on mollusks. Upset that balance by eliminating mollusks and it can do considerable harm.

Some people raise mollusks for food, as they are high in protein. Escargot is considered a delicacy, as is abalone. And the bivalve oyster is not only a source of good eating, but also of pearls for necklaces.

Research suggests there are also benefits to mollusk mucus — the substance that creates that milky looking slime trail in your garden.

Ancients used mollusk mucus to treat spells of fainting and bouts of coughing up blood, as well as general pain relief. They also boiled and ate mollusks whole, and created an edible paste from the crushed shells.

More recently, creams and gels with a mucus component have made their way into drug and health food stores.

Spreading mucus is a defense mechanism for the mollusk. It is a very slippery liquid, slippery enough that it can cause an attacker to lose grip and traction.

You can also purchase slugs and snails for pets for children. You don’t need a collar, license or any vaccinations, just a food source and a simple enclosure to serve as a pen.

Elaine Rohse can be reached at


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