Offered a chance for some deep, rich black earth for gardening in a tiny Southeast Alaska village, I asked if there were any black slugs in it.
“If you’re going to garden here you have to just get used to them,” a resident curtly told me.
And with that began my battle and fascination with the invasive giant black slug known as Arion ater.
Tenakee Springs in Southeast Alaska, with a population of 120 souls in the summer and possibly a third of that in the winter, lies 62 nautical miles (there are no roads to it) south of Juneau. Sitting on Chichagof Island deep in the Tongass National Forest, Tenakee is surrounded by secondary and old-growth forest.
Southeast Alaska is blessed with bountiful summer sunshine of close to 18 hours, lots of water, dirt from the forests, and rich alluvial soil from its many streams and rivers.
I once lived in Skagway, the self-proclaimed “Garden City of Alaska,” 90 miles north of Juneau, but never encountered black slugs before moving to Tenakee Springs.
How did they make their way to Tenakee — and how do gardeners here either kill or deter them?
Slugs on the move
Like so many invasive species changing environments worldwide, their journeys begins far away and are transported either by ship or plane secreted in soil, food, or lumber shipments. Native to Europe, the black slug has invaded Australia, Canada (British Columbia, Newfoundland, Quebec), and the Pacific Northwest including Alaska.
The Alaska National Heritage Project, part of the University of Alaska Anchorage’s Alaska Center for Conservation Science, keeps track of invasive species, as well as the state’s animal and plant species ecosystems, and their ranking as a conservation concern.
ANHP published an invasive ranking for the black slug based on distribution, biological characteristics, ecological impacts, and feasibility of control. These categories were assigned points, and Arion alter received a 62/100, or “moderately invasive.”
But you wouldn’t know that when viewing the march of slugs up and down “The Trail,” the only road through town and where cars and trucks are not allowed. It’s four-wheelers, bicycles, or feet.
The wonder of them
I have to admire black slugs for their drive to survive. They’re also — aside from the curious, but also creepy breathing hole on their side — a creature uniquely suited for survival.
According to Wikipedia, “Like other terrestrial slugs, the black slug is a hermaphrodite, preferring to find a mate, often several, but can self-fertilize. After mating, the black slug seeks a dark, moist environment such as beneath mosses and occasionally within topsoil, to lay its eggs of about 0.2 inch in diameter. Between August and October, an individual slug lays up to 150 eggs every one to three weeks with clutches diminishing to 20 eggs late in the season. Juveniles hatch after at least twenty-seven days, hatching later under cold temperatures. Maturation takes up to nine months, enabling mating in early summer. Black slugs die shortly after laying its last clutch, rarely surviving into a second year.”
With that breeding power, they are able to overrun an area and demolish the native slug species in Southeast, the Pacific banana slug, Ariolimax columbianus, the second-largest terrestrial slug on Earth at almost 9.8 inches long.
Plus, black slugs are highly aggressive. A friend and I went for a walk up the forest trail and found slugs everywhere, but one in particular was beginning a face-off with a banana slug.
Arion alter is present in Alaska in Anchorage, Cordova, Yakutat, Gustavus, Juneau, Sitka, Tenakee Springs, Ketchikan and Kodiak Island, according to the Alaska National Heritage Project.
Black slugs do provide some positive effects on seed and spore dispersal in the forest through their fecal matter, but for gardeners their presence is a never-ending chore and source of frustration.
Boasting 27,000 teeth, the black slug is a natural wonder of machine-like destruction. Their flexible band of microscopic teeth, called radula, acts like a circular saw and they can grind through plants without slowing down.
Doing battle with slugs
On July 4, Tenakee used to have a slug toss, but it was decided that was perhaps too callous an approach to a creature just living its life.
There has been research into whether slugs feel pain, but because animals like lobsters, snails and worms have simple nervous systems and lack a cerebral cortex needed for higher emotion processes, researchers surmise they do not experience pain.
One Tenakee resident walks down the trail most days and cuts slugs in two — an execution method considered humane and does not cause the slugs to grow back either segment.
I once saw several slugs surrounding their mangled comrade and, because I tend to anthropomorphize every life form, asked my trusty companion Bruce Ware if they were mourning their fellow slug.
“No, they’re eating it,” he replied.
So while the lack of compassion in slugs is disappointing, this method does bring others in for an easy kill and avoids the tedious search for them among the vegetation.
I, however, prefer to chop them directly in the head regardless of whether they have a cerebral cortex, because I think it kills them instantly and if they possibly detect pain then it is but a brief stab.
Other Tenakee gardeners have their own preferred methods.
Most spring mornings, you can see Joni Gates down on the shore of Tenakee Inlet picking seaweed for her garden, but also gathering clam shells to break up so the jagged pieces befuddle slugs attempting to enter her property.
Usually this works, she says.
An archeologist by way of a college degree, she says she never went on a dig preferring office work, but now tills the soil in her yard and grows a variety of flowers. With the white jumble of sharp, broken clam shells as a backdrop, the flowers are a standout every summer.
Joni also has tongs to lift the slugs up and dumps them into a container of seawater, which kills them. Most Tenakee gardeners use tongs with rubber ends to grip the slug securely. No one ever picks them up by hand because of its three noxious forms of mucus, the first two are thin and aid locomotion, and a thicker one is secreted along the slug’s length with all contributing to their wave-like motion.
Bruce picked one up barehanded and swore the mucus moved up his bare arm like something in a horror movie.
In the Tenakee Community Greenhouse, which is attached to the community coffeehouse New Moon Café, Carlene Alred oversees the greenhouse and is vigilant for any interlopers in the soil so no plants are ever introduced to the raised beds, and soil is carefully inspected and improved with organic pellet fertilizers and seaweed slurry.
I decided the deck, being 20 feet off the ground, would be a safe place to plant in containers, and ordered 100 pounds of soil from a hardware store in Juneau. I began in March to raise plants by seed in the house by a big window that gets lots of sunlight. No slugs, but there were fungus gnats, which were fought with soapy water sprayed on the soil and leaves.
Or were there truly no slugs?
One day, I saw one inside at the sliding door near the table the seedlings were on, then another outside the same door. Did they shimmy up the gutter pipe, did they come in the soil? I’ll never know, but I did add a sunken plastic container filled with beer (you can use sugar too if beer becomes too expensive), but no other slugs ever appeared in the brew.
I also built a raised bed out of a picture window packing crate, which came with six-inch sides and a particleboard bottom. With two-by-fours added for height at each corner, chicken wire to keep the deer out, and plastic overhead to deal with the deluge of rain experienced in a rainforest, I was able to grow a good crop of broccoli.
I kept the slugs from crawling up the legs with a heavy smearing of Vaseline, but really any kind of grease will do. It seems to foul up the movement of the snail and I’d find them on the ground curled up lifeless like Little Engines That Couldn’t.
Other methods of protecting plants from slugs include tenting seedlings, homemade barriers made of sawdust, crushed eggshells, ground oyster or clam shells, soap, or cinders from the fireplace.
But gardeners of Tenakee have learned, no matter what they do, those resilient black slugs are here to stay and they’ll just have to deal with it.
• Dimitra Lavrakas is an Alaska author and journalist who has written for publications including the Skagway News, Dutch Harbor Fisherman, Alaska Business Magazine, Arctic Sounder and Anchorage Daily News.