How far should you toss a snail?

Have you ever wondered where slug and snail eggs are laid? Or how fast and how far slugs and snails can move in a night? How about tossing them out of your garden, if you don’t like killing these invertebrates? Or why, when on morning slug patrol, day after day, there seems to be no lack of these animals in your garden? I think about all of these topics when I'm in my garden.

Slugs and snails are mollusks, one with a shell, one without, that moved to land from water millions of years ago. It’s been a successful shift for them. Mollusks are one of the most prolific and diverse animal phyla on earth; the air-breathing species are both abundant and widespread. These species no longer need to live in water for any stage of their life cycle. In our temperate and humid climate, several species are very much at home in gardens.

Dandelion leaves are smooth, thin and sharply lobed, and grow in low rosettes with one flower per stem. It flowers in spring and again in fall.

Rosettes of hairy cat's-ear are thick, dotted with hairs and roundly lobed; plants grow in thick rosettes with several flowers per stem. It flowers from summer into fall.

Eggs are laid under plants in the soil to keep them moist. Introduced daisies, including hairy cat’s-ear, Hypochaeris radicata, and dandelion, Taraxacum officinale, are good covers for European slugs and snails. Native slugs and snails prefer damp forest duff layers, and do not lay eggs in gardens. Eggs are soft walled and flexible. They need to stay moist if the tiny creatures are to survive and emerge. Eggs are laid in mid to late spring; young slugs and snails hatch two to four weeks later.

Hatchlings eat their way out their eggs, then the tiny mollusks begin a life of eating and growing. Native slugs and snails eat fungi, decaying wood, and mosses in the woods. Introduced species prefer garden plants and do not normally enter natural woodlands.
Natural pests include many birds, especially when the mollusks are very small. Chickens will eat both eggs and young. Ducks and garter snakes prefer the larger animals. In fact, garter snakes are excellent slug predators. A nice warm compost pile, a few smooth warm rocks to bask on, a source of freshwater in the garden, and you have all the amenities of life that a garter snake prefers, along with fresh slugs and snails for them to eat.

A young slug on a cat's-ear leaf hatched just a few days ago. All of the mollusks that use leaf rosettes in lawns for egg cover and food are introduced species; most are from Europe.

Like deer, European slugs and snails have cosmopolitan tastes––they will browse anything new at least once while deciding if it’s edible or not. One year I planted a native orchid, carefully enclosed it in a ring of slug bait, went back to the house for the durable tag––and when I came back out a few minutes later, a spotted leopard slug and a brown snail were circling the bait ring, enticed by the new plant. The next year, they left it alone.

A leopard slug (lower left) and European brown snail (at top) circle a new plant in their food space, a native stream orchid. These mollusks found the orchid within minutes after it was planted in early spring. The light ring is slug bait, the dark layer beneath is compost. The slug is arching up over the bait to smell the plant; the snail tasted the bait and is withdrawing.

If you aren’t comfortable cutting, crushing or salting these animals, is tossing effective? How far must you toss a snail or slug to keep it from coming back? Several scientists in England who are also gardeners studied this in their own gardens and neighborhoods. 

One man used dots of white paint on snail shells, and tossed them out of his garden, over two fences onto open land, adding a dot every time a previously marked snail showed up. The record holder was a snail that returned 17 times. The average time to return was a month. The next year, he worked with a statistician, numbered the snails and either tossed them (even numbers) or moved them about 70 feet (20 meters) to another garden (odd numbers). Only 3 of 151 odd-numbered snails returned.

Another gardener tested snail homing abilities by painting numbers on her snails, persuading her neighbors to do the same, all using different colors, one color for each garden, then swapped them around in the neighborhood. She found that snails can often find the way back, over a distance of about 32 feet (10 meters).

An ecologist working with her was intrigued by this finding. He attached LEDs to some snails, and painted others with glow-in-the-dark paints. Using time-lapse photography, he found that snails move about 1 meter (3.2 ft) a hour at top speed, and could move up to 10 meters (32 ft) per night. “In wet weather, they form convoys, sliding along the slime trails of preceding snails, which Hodgson suspects helps them save energy.” (New Scientist, 12 July 2014, page 37) To see a time-lapse video of LED-marked snails, go to http://www.thisiscolossal.com/2013/08/timelapse-video-of-hundreds-of-snails-tagged-with-leds-at-night/ 

If snails keep returning, is tossing useful? Yes, because it may help give plants a break in being eaten. They grow stronger with a few days of rest from munching, and when the snails return, plants are better able to cope with the damage. The farther away the snails are taken, the fewer return; 20 meters (70 ft) is good as a tossing/moving distance, but even 5 meters (16 ft) gives plants a few days break.

Both slugs and snails can be seen determinedly gliding somewhere, heading for their preferred foods in my garden when weather is cloudy and moist. This is a good time to practice slug and snail tossing. Just don't toss them into your neighbor's garden!

Think of this patch of hairy cat's-ear as a slug factory, capable of hatching thousands of baby slugs each year. It's also a late summer nectar source for Woodland Skipper and other butterflies. 

Published October 22, 2014 in the Chinook Observer. 

Weeds, or not: Gorse, geraniums, bluebells and daffodils

Kathleen Sayce

Written April 14, 2014, published April 23, 2014; all flower photos by Kathleen Sayce. Bulb farm photo by Charles Fitzpatrick, courtesy Columbia-Pacific Heritage Museum. 

A few weeks ago, Sondra Nash Eaton (local resident and manager, The Cove Cafe) posted a photo on Facebook after a walk in the woods, extolling the beauty of early flowering wildflowers. Her photo showed herb Robert, Geranium robertsianum, one of two aggressive geraniums that are moving into this region (the other is shiny geranium, G. lucidum). Both came in with nursery plants propagated in other areas, riding along in pots. Both are quite capable of crowding out other perennial herbs, and over time severely reduce species diversity. Sondra was annoyed when I pointed out that her lovely pink flowers were actually aggressive incomers, which led me to discuss why some plants go onto noxious weed lists while others don't. 

The key characteristic is how well each plant gets along with others, not just in a yard or back woodlot, but over a wide geographic area. Most incoming species settle in and coexist alongside the rest. A few, and it's only a few, exhibit a tendency to habitat dominance, if not world dominance, and it's those few that become chronic headaches for foresters, ranchers, farmers, and gardeners. 

What are some of the problem species in this area? I discuss a few of these in the following paragraphs. To see the official lists of noxious weeds, go to http://www.nwcb.wa.gov/nwcb_nox.htm , posted by Washington Department of Agriculture.

Gorse has sharp long spines and highly resinous wood; it burns easily, provides nectar for late winter to early spring foraging bees, and habitat for wasps.

Gorse, Ulex europeaus, is in the pea family, has yellow pea-shaped flowers and long thorns, is highly resinous, and can colonize bare sand as well as grasslands, including dunes along the ocean. It burns hot in fires, and helps fires jump into forests. Seeds live decades in the soil. 

Scots broom is similar to gorse, minus the thorns, and blooms in early to mid spring. 

A cousin, Scots broom, Cytisus scoparius, also has pea-shaped flowers, white to yellow to red, no thorns, the same ability to colonize sandy soils, and long lived seeds. Once established in a grassland, only a few small grasses, herbs and mosses grow beneath these woody shrubs. Hummingbirds may nest among gorse thorns, safe from many predators. Yellow-jackets like gorse for their nests too, as bears and other animals that eat wasp larvae are less likely to go into gorse thickets. A few summers back, a neighbor's gorse thicket had five yellow-jacket nests within about fifty feet of each other. 

Atlantic ivy carpets forests, woodlots and damages shrubs and trees. Once vines reach tree canopies, the leaves act like extra sails and help topple trees during windstorms. 

Atlantic Ivy, Hedera hibernica, and English Ivy, Hedera helix, are evergreen vines that swamp shrubs and buildings, and strangle trees. Native to mountains in Hungary, no effective biological control has been found there, where these vines are minor forest components. Birds eat the berries and spread the seeds widely. Deer like to browse on the tips, but they don't kill back the plants. Vines start flowering once they begin growing off the ground, and provide winter to early spring nectar for honeybees. A well established ivy patch can carpet the ground and trees, and shade out all other species. On buildings, ivies pull off siding, crack mortar, and push into interior spaces, lift off roofing, and open up walls to rain, mice, molds, and other species. Large spiders like to live in ivy. I pulled ivy off a Douglas-fir in my front yard a couple of years ago, and dozens of large spiders bailed out of the foliage as it came down. Once the vines reach the leaf canopy of the tree, their leaves act like sails, and windthrow problems increase, making these trees much more likely to fall during storms. 

The formal list of noxious weeds is long, and I could continue, but instead, let's look at incoming plants that have not displaced other plants or changed habitats, are not on the noxious weed list, but can be weedy to some people. Two of the showiest are bluebells and daffodils. Both arrived as ornamental bulbs from Europe, and both have toxins in their bulbs that make them unpalatable to voles, squirrels and other animals. 

Bluebells, Hyacinthoides species, grow in dense patches in lawns and gardens. Flowers are white, pink and blue.

Bluebells, Hyacinthoides species and hybrids, have blue, pink and white flowers. These spring-flowering bulbs from Europe naturalize easily and spread around gardens via bulbs and seeds. Deer occasionally nip the flower tips. Hummingbirds feed on nectar in the flowers, as do bumblebees. They can grow into dense patches and are especially pretty under hardwood trees in spring, where they grow mixed with grasses, dandelions and fringecups, all of which can be mowed once flowering is past.  

Daffodil field north of Nahcotta on Joe Johns Road, planted by John Morehead, early 20^th Century. Photo by Charles Fitzpatrick, courtesy of Columbia-Pacific Heritage Museum. 

Daffodils, Narcissus species, are showy spring bulbs. They were cultivated here and on Clatsop Plains for the cut flower trade early in the 20^th century. Bundles of flower buds were shipped out by boat and train to urban markets. Air freight ended these local businesses, because flowers grown in California could reach markets a few weeks earlier and get top prices. Old fashioned daffodils live on in many areas to this day from those early commercial plantings.  

Many bulbs persist for decades after planting; these 'legacy' bulbs can mark former homesteads in forests, and also delineate where past generations of gardeners worked in present day gardens. For more on legacy bulbs, see http://www.pacificbulbsociety.org/pbswiki/index.php/LegacyBulbs  on the Pacific Bulb Society website. 

Dandelion is a widespread perennial herb in gardens and fields throughout North America. Spring flowering, the seeds are dispersed by air. Its summer flowering counterpart is hairy cat's-ear. Both provide habitat for European slug eggs and young. 

Dandelion, Taraxacum officinale, is a tap-rooted yellow daisy that flowers in spring and lives most of the year as a rosette of leaves. For turf purists who want a grass-only lawn, this is one of several annoying daisies that seeds into bare patches of grass. Another is hairy cat's-ear, Hypocharis radicata, which also lives year round as a rosette, and flowers during summer and early fall. Both are perennial, both have yellow flowers, and both provide nurseries for introduced slugs.  

English daisy is a low growing perennial herb that often lives in lawns. Like dandelions, this daisy provides nectar for native insects.

A white flowered daisy, English daisy, Bellis perennis, also lives in lawns and tolerates mowing, with flowers shorter than mower blades, it grows in small low patches among turf grasses and mosses. 

Note that all of these species are considered weedy by someone. Yet the first group of plants (geraniums, gorse, Scots broom, ivies) can completely change a plant community, the latter group (bluebell, daffodil, English daisy) cannot. That's the litmus test for invasiveness:  Does the original plant community persist when a new plant arrives?  Most of the time, the answer is yes. Most of the time, that plant joins the group of plants that already grow here. Occasionally, a newcomer changes the entire shape of the plant community, and crowds out other species. Those plants end up on noxious weed lists. The rest settle in and join the crowd, becoming just another member of the local photosynthetic gang.