By Erin Marissa Russell
Ever wondered where slugs come from at night? Trying to keep your garden safe from slugs can be maddening. It seems like each night, these mollusks launch an invasion to munch on your garden’s tastiest, tenderest leaves. We’ll tell you about where slugs come from at night as well as how to keep them at bay in this article.
Slugs are nocturnal creatures that come out to do their eating at night. During the daytime, they sleep in spots that are cool, damp, and dark. You may be able to find out exactly where the slugs in your garden are coming from by following the telltale silver trails they leave behind. These silvery markings are made of mucus and help the slug stay hydrated while also providing a protective coating that helps the slug glide over the ground or your plants.
To look for the slug’s hiding place, start at your damaged plants and trace the silvery path backward. You may just find the mollusks are sleeping in nooks and crannies in brickwork or under an object that casts shade during the daytime.
When the weather gets hot and dry in the summertime, slugs don’t disappear. They find a moist hiding spot or bury themselves in the cool earth to wait out the weather. They create a cocoon, which is dissolved once there’s enough moisture in the environment for the slug to live comfortably.
Slugs are adaptable creatures that can lose up to half their body weight when they’re in suspended animation inside the cocoon. It only takes about two hours of rehydrating for the slug to return to its original weight.
1. Know When Slugs Tend to Strike
Because they favor cool, moist conditions, slugs are at their worst in the springtime. Knowing this empowers you to be on the defensive in spring with preventive treatments like those we’ll discuss below. Damage from these creatures can also be quite serious in late summer, when the weather gets wetter and cooler.
2. Use Cultural Control to Prevent Slug Damage
There are several ways to make your garden a less welcoming spot for slugs. Make sure there’s enough space between your plants for air to circulate and the ground to stay dry. Overly wet conditions create the perfect place for slugs to hide.
You’ll also want to avoid overwatering your garden to keep things from getting too moist. For a simple way to test the moisture level in your garden soil, stick a finger down into the soil to a level of about one inch. If the soil feels moist or clings to your finger, it’s not time to water again just yet. When your garden needs water, the soil won’t feel wet at all, and it won’t stick to your skin, either.
If you use mulch, keep the layer to a maximum of one inch. This will keep the soil from retaining too much moisture while still keeping plants hydrated.
In autumn, rake up fallen leaves from garden beds or other areas where plants are growing. Rake again in early spring to pick up the moist, wet garden debris that slugs love to use as a habitat. You’ll also be raking up some of the slug eggs in your soil, if those are present.
Finally, do not use grass clippings in your garden, as they are a convenient food source for slugs. Large wood chips are good slug habitats and should be avoided for this reason.
3. Trap and Discard Slugs
Make your own slug traps with carpet squares, boards, pieces of cardboard, or sheets of moist newspaper, about a foot tall by a foot wide. Lay these out on the ground near plants that have been damaged by slugs. Wait a few days, then check the underside of the traps.
Remove any slugs you find and drop them into a bowl of soapy water. Alternatively, after you pull up the traps, you can turn them upside down and scrape the slugs you’ve caught into a plastic food container. Then put the plastic food container full of slugs in your freezer for three hours. After three hours, the dead slugs can be discarded or even added to the compost pile.
You can also make traps simply by laying melon rinds in the trouble spots of your garden, with the rind up and the side with melon on it pointed toward the ground. Slugs will collect on the underside of the melon rinds, too. Old-fashioned advice about how to kill slugs recommends using this method with lettuce, spinach, cabbage, and raw potatoes. In the morning, the veggies are picked up to collect and destroy the slugs on their undersides.
You have probably heard about beer traps being used to collect slugs. Just bury a shallow container (food containers are good for this) with only about half an inch of the rim staying above ground. Then fill it with beer. If you don’t keep beer in the house, you can mix water with a little molasses, cornmeal, flour, and baking yeast to create a beer substitute. Slugs will go into the beer trap on their own and drown.
If the weather will be rainy, find a loose cover for the beer trap that will prevent the beer from being diluted. You may find that some of the slugs crawl out of the buried beer trap. If this is happening to you, you may want to make a trap that is guaranteed to keep slugs inside.
Get a plastic beverage bottle and cut the top off right where it joins to the widest part of the bottle. Then turn the top upside down so that the opening is pointed down inside the bottle. Use staples or duct tape to keep it in place. You don’t have to bury this trap. Simply fill it with beer or the beer substitute we described above, then place it in the garden near slug-damaged plants, turned on its side.
4. Encourage the Presence of Slug Predators
Why go it alone against your local slugs when you can enlist the help of natural predators? Lots of creatures feed on slugs, including chickens, ducks, firefly larvae, frogs, ground beetles, snakes, songbirds, and toads. Find out more in our articles The 5 Best Tips to Raising Backyard Chickens, How to Attract Frogs and Toads to Your Garden, How to Attract Fireflies or Lightning Bugs to Your Garden, and How to Attract Birds to Your Yard and Garden.
5. Spread Alkaline Materials to Keep Slugs at Bay
Slugs don’t like alkaline soil, though lots of plants thrive in it. You can increase the alkalinity in your garden by amending the soil with substances like cinders, sand, slag, slaked lime, and wood ashes.
6. Fight Back With Slug Control Sprays
Alcohol and cold coffee can both be used to control the slugs in your garden. Cold coffee will only work if the slugs are small and you are able to drench them completely.
For an alcohol spray, you can use either rubbing alcohol or grain alcohol (ethanol). You just need to make sure the rubbing alcohol is additive free. You can use either 70 percent or 95 percent rubbing alcohol. It works well, but the grain alcohol works even better.
If you’re using 70 percent rubbing alcohol, make a mixture of one part alcohol to one part water. If you’re using 95 percent rubbing alcohol, make a mixture of one part alcohol to one and a half parts water. This spray should be aimed directly at slugs that you can see, not sprayed on plants as a preventive measure. The spray will kill slugs by penetrating the mucus layer on the outside of their bodies.
7. Avoid Ineffective Remedies
A few commonly recommended slug control methods aren’t as reliable as the ones we’ve listed here. You’ve doubtless heard gardeners talk about pouring salt on slugs to kill them. Going on the offensive by stalking individual slugs to kill is not an effective way of protecting your garden.
Neither is pouring a line of coarse material around your plants, like coarse sand, coffee grounds, crushed eggshells, diatomaceous earth, or pine needles. The idea is that the slugs won’t be inclined to drag their tender bodies across these rough materials. However, encircling plants with these substances to prevent slugs has not proven to be effective.
If you’ve been wondering where slugs come from at night, the first part of this article answered that question in depth. While their specific hiding places vary from one yard to another (and we’ve talked about plenty of potential spots), slugs always sleep the day away somewhere cool, moist, and dark. If you’re curious about exactly where your local slugs come from, you can try tracing the slug’s silvery trail backward from damaged plants.
But just knowing where slugs are coming from won’t do a thing to keep them out of your garden and keep your plants safe. That’s why we also covered preventive measures and steps you can take to fight slugs off. Pick one or two of the steps that are most convenient for you, or you can try more than that if you have a real slug invasion happening.