Is your Alberta garden plagued with slugs?
Are unsightly holes disheartening your hostas?
In this blog, we will talk about the life cycle of slugs, where slugs typically live, how slugs damage plants and share some simple and effective ways to get rid of slugs in your garden.
What are Slugs?
Slugs can be thought of as shell-less snails. Most slugs in Alberta are grey or brown or a mottling of these two colours. Slugs are legless soft bodied animals that have one foot called a monopod (‘mono’ meaning ‘one’ and ‘pod’ meaning ‘foot’).
Slugs range from .75 cm (¼”) to 5 cm (2”) in length. Fortunately for us in Alberta, we see slugs that are on the smaller end of this scale. Rarely do we see slugs that are larger than 2.5 cm (1”) long.
Slugs have 2 pairs of feelers – a large set and a smaller set.
Their large feelers are located on the top of their heads and these are the ones that have eyes.
The smaller, lower pair is harder for us to see and that set is for smelling.
Slugs are covered with a slimy coating that protect their soft bodies from a variety of threats like predation and desiccating. Keeping moist is a key factor in slug survival and habitat choice. Slugs also use this slime to lubricate their locomotion as they propel themselves through their environment. Slime leaves shiny telltale trails as to where they’ve been and what plants they have been visiting.
Signs that you have slugs in your garden include irregular holes in leaves, shiny trails, and excrement on leaves.
The Lifecycle of a Slug
Due to their necessity in keeping their outer skin moist, slugs live in damp, cool, and shady areas. Cool and shady habitats decrease metabolic needs and lower the evaporation rate of moisture – that’s what makes any shade garden is prime real estate for these creatures.
Slugs live throughout the growing season – there are many variations in how they emerge and grow through the season from spring to fall. Slugs generally don’t have one flush of hatching like Scarlet Lily Beetles, for example, but eggs hatch and populations increase as the season wears on. How quickly the population increases depends on how wet the weather is. Slug populations grow at a faster rate in rainy years.
Many strains of slugs lay their eggs in autumn once the young slugs have matured to adults. Some lay eggs in clusters and others lay them singly. Slug eggs range in colour from translucent to white to golden.
Slugs deposit their in the soil or underneath things like leaves or mulch, rotted plant material, pots, logs, old boards, stones, and any material or accents like birdbaths or benches in a garden.
Some slug species hatch in the autumn with the baby slugs overwintering underground during the cold season. And other slug species lay eggs tough enough to survive our Alberta winters. Slug eggs can stay in limbo for years, until the conditions are right for them to hatch.
Baby slugs are quite vulnerable to predators like birds, snakes, beetles, spiders, amphibians, and other slugs.
How Slugs Damage Plants
Slugs are nocturnal – meaning they feed by night and hide by day.
‘Feed’ being the operative word — slugs sure do have voracious appetites. Some species even eat the equivalent of their weight each day!
Slugs are omnivores, meaning that they eat both plant and animal material.
They are even cannibalistic.
On the plant side of things, slugs feed on green plants, algae, and even fecal matter (there is so much potty talk in gardening).
Slugs have a special affinity to seedlings, ripening fruit, and decaying plant material. On the animal side, slugs have been known to eat insects, worms, carrion, and even other slugs.
Slugs feed with an eating apparatus called a ‘radula’. A radula is a small many-toothed instrument that scrapes or cuts food like a rasp or a file.
These sharp backward facing teeth repopulate continually. This is what causes the irregular leaf and hole damage.
Plants That Slugs Love to Eat
Here are some popular plants that slugs can’t seem to get enough of:
- Green leafy vegetables
- Hostas (thin-leaved hostas)
- Leopard’s Bane (Doronicum)
Plants That Slugs Don’t Like
Slugs, like deer and rabbits, will eat almost anything if their survival depends on it. But they prefer to avoid plants that are highly scented, highly flavoured, have milky sap, are prickly or hard to chew.
Here is a list of the plants they side-step:
- Astilbes – hard to chew
- Bleeding Heart (Dicentra) – bad taste & smell
- Clips/Bell Flower (Campanula) – bad taste
- Columbine (Aquilegia) – bad taste
- Cushion Spurge/Spurge (Euphorbia polychroma) – milky sap
- Creeping Phlox (Phlox subdulata) – prickly
- Daylilies (Hemerocallis) – hard to chew
- Jacob’s Ladder (Polemonium)
- Lobelia – bad taste
- Mint – bad taste
- Ornamental Grasses – hard to chew
- Periwinkle (Vinca) – hard to chew
- Silver Mound (Artemesia) – strong fragrance
How to Get Rid of Slugs in Your Garden
Without further ado, let’s dive into a few of our favourite ways to get rid of those slippery little slugs in your garden.
If you combine a few of these together, if will make your efforts even more successful.
Remember that the operative motive for slugs is to keep its outer body covering moist, so moving around at night best accomplishes this.
1. Design a Gardens with Plants that Slugs Won’t Like
Use the lists we’ve created of plants slugs love and plants slugs hate to plan spaces that are less attractive to slugs. The more plants you grow that are inhospitable to slugs the less likely your garden is to attract them.
Plant a trap crop like Marigolds. Slugs are attracted to Marigolds, so you can find them there easily.
2. Remove Damp Material from Your Gardening Space
Since slugs thrive in areas that are damp and wet, reducing materials that create a moist environment will contribute to a lower slug population.
How To Reduce the Dampness in Your Garden
- Consider Mulch – Consider the pros and cons of mulch. If slugs are an issue in your garden, mulch could be contributing to it. Some people find that mulch encourages a large slug population. If that is the case, think about keeping mulch just around the base of the plants, or eliminating mulch altogether.
- Remove fallen leaves – Remove leaf litter in the spring, eggs may be underneath.
- Keep it tidy – Eliminate elements that encourage slug habitat like old boards, large wood chips, old stumps, stepping stones, and other large materials like this from your garden. Slugs love to shelter under these and lay their eggs under these kinds of objects too.
- Reduce moisture – Water your garden only when it is necessary to reduce moisture in shady areas. Most shade gardens need very little supplementary water.
- Create space – Thin out plants to improve air circulation to dry things down a little in damp areas. You can also try clearing out lower leaves to enhance air circulation and to make it more difficult for slugs to climb on.
3. Track Slugs Down and Get Rid of Them
Slugs can be found a couple of different ways:
How To Find Slugs During the Day
Follow the slime trails in the early morning that slugs leave behind to give clues as to where they are hiding. You can often find slugs hiding at the base of plants where the stems emerge from the soil, hanging out on lower stems, and on the underside of leaves.
How To Find Slugs at Night
You can hunt slugs at night in the dark or at dusk with a flashlight – headlamps are even more effective. Slugs get bold at night and they can be easy to find. Slugs will crawl around on the top of the leaves and hang out on stems.
How To Remove Slugs From Your Garden
Have you spotted a slippery slug? Here’s what to do —
- Handpick slugs off and dispose of them – Using gloves for this is highly recommended. (Who wouldn’t use gloves for this slimy activity?) Because of their eating habits, slugs can be carrying around bits of harmful bacteria or parasites. Wash your hands well after.
- Spray Slugs with a 20% Ammonia Solution – Use 1 part regular household cleaning Ammonia to 5 parts of water (try adding ¼ cup ammonia to 1 cup of water). The ammonia will strip off the slug’s protective mucous layer and they will die immediately from drying out. This solution does not affect plant leaves or other creatures, like birds.
4. Slug Barriers and Slug Traps
There are other natural ways of discouraging slugs by using slug barriers and slug traps.
Slug traps draw slugs away from the plants and them into a trap of some kind.
While slug traps are quite effective, slug barriers can also work very well.
The idea with slug barriers is to keep slugs from getting on the plants and leaves by creating a rough or prickly surface which is meant to irritate and damage their bellies or their foot.
Here are some of the most effective slug barriers and traps:
- Slug tape or copper tape
- Diatomaceous earth
- Slug traps
How To Use Slug Traps
Dig a little hole in the ground for a shallow dish like an aluminum pie plate, a wide lid from a container or any other kind of dish like this and place it even with the ground so the slugs can access them simply.
Place bait in the traps to attract the slugs. Slugs are attracted to cucumbers, and slugs are very fond of beer.
5. Encourage Natural Enemies
Slugs have natural predators such as amphibians like frogs & snakes, chickens, ducks, other birds.
Growing a variety of plants like annuals, perennials, and vegetables provides habitat for many species of beetles, spiders, and small amphibians which are prey on slugs.
Adding a bird feeder and bird bath encourages birds to visit your yard regularly.
6. Use Repellants
There are commercial slug bait formulas on the market for purchase.
When considering these alternatives be sure to check that the animals that feed on slugs will not be negatively affected by them.
In the long run, slug traps and slug barriers are very effective so that chemical use isn’t necessary.
Final Thoughts on Getting Rid of Slugs in Your Garden
Slugs can really put a damper on gardening, especially a shade garden.
By incorporating the right plants to decrease a garden’s appeal to slugs and strategies to discourage them with barriers and eliminate them with traps, they can be manageable.
Feel free to contact us with any questions or concerns you may have with eliminating these garden pests.
– by Sharon Wallish Murphy