Why Is My Yard Full of Slugs?

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Just because you see slugs and snails in your garden doesn’t mean that you have an infestation on your hands, but you shouldn’t ignore the fact that you now have guests in your lawn, either. There are good and bad sides to a garden full of slugs.

You might find a few slithering about your sidewalk after a rainy day or during the night when you forgot to turn off the sprinkler. You might look at the first one and be fascinated; perhaps take a few pictures and then let it be. However, as more and more start popping up, you might start wondering, where are they coming from? Why is my yard full of slugs?

Slugs love to snack on dried leaves, flower buds or fruit that is almost ripe. Furthermore, they thrive in damp areas, especially moist sand. If you combine all of these things and think of a place that has all of that, you will find that the best place for slugs is, in fact, a garden. Their larvae attach to bird feathers or get mixed in the dirt you add. All it takes is just a couple of slugs to give eggs and increase their population.

What Do Slugs in My Yard Mean?

Slug on leaf

In the olden days, slugs were considered to be leeches’ cousins (which they are, to some extent). Where leeches were used for medical purposes, slugs and snails were used as weather detectors. There is an old adage:

When the black snail (or slug) doth cross your path, black cloud much moisture hath.”

This means that if you have a snail or slug running away from a lawn and there’s no concrete or stone, you can expect rain. If it is climbing a tree, expect hot weather. If slugs are burrowing into the ground in the summer, a drought is coming. And lastly, if a slug is burrowing into the ground in autumn, winter is coming. Actual winter; not white walkers.

However, as time passed and modern weather forecasts came to be, slugs didn’t become redundant. As we mentioned above, slugs love to munch on dried leaves, rotting vegetables and fruit, and other debris on ground-level, thus cleaning the ground. By doing so, they effectively recycle organic matter by turning it into nutrients essential for plant-life.

According to superstition, since slugs are pure muscle, they are an omen of great hidden strength as well.

On the other hand, slugs in large quantities can actually be very dangerous for your plants. If you see three or four slugs roaming about your lawn, expect at least a hundred of them in your lawn. Of course, the bigger your lawn is, the more slugs you will have.  

Slugs secrete a slimy mucus or ‘vomit’ that can result in food poisoning for your pets. They also carry lungworms, which can turn into a round worm inside the intestines and lead to infections in animals and humans. Slugs usually feed on dead leaves but may also develop an appetite for fresh leaves near the ground, such as spinach, mint, thyme, and even grape vines.

Some slugs can resort to eating roots, effectively killing plants from the underside.

Where Did the Slugs Come From?

Slugs like to hide under moist plant debris as the mulch on them during the night. Slugs also wriggle and make room for themselves under rocks, weeds, and fallen logs. The key ingredient that invites slugs into lawns is moisture.

Slug larvae are rather sticky and can stick to bird feathers and drop into your lawn when they land. Their larvae may also be present in the dirt you buy to replace topsoil or a new plant you just bought. All it takes is just one slug to enter your lawn and within 6 months, you can expect them to grow in number exponentially.

As mentioned above, during summers, slugs may choose to burrow themselves deep into the dirt to protect themselves from an upcoming drought. This is because moisture is a key requirement for snails and slugs to survive. If conditions become too dry, their outer skin starts to shrivel up, closing the pores through which they ‘breathe’, effectively killing them.

Primary Causes for Slug Infestations

In the UK alone, there are more than 40 different slug species out of the 48 known to us. In the US, there are 29 different species, while in the hottest regions of the Middle East, there are 9 different native slug species. This shows that slugs are native to almost every corner of the world, so it is natural to find one in your lawn.

Of course, they have natural predators to look out for, as well, to keep their population in check. Slugs are considered ‘timid’ invertebrates since they are hunted down by almost every vertebrate group on the planet, i.e., by reptiles, birds, amphibians, and mammals. If your lawn has frogs and you choose to use a chemical treatment that caters to frogs, you can expect a slug infestation to begin.

Another reason slugs may make their way into your lawn could be ‘chaos’, i.e., debris on the ground or haphazard grass and planting techniques. Nature isn’t timid or trained; it’s wild. As you let your garden go wild, you can expect not just snails and slugs to thrive, but a whole new biome of invertebrates and vertebrates looking for food.

If you have plants that make a lot of mulch, you should consider cleaning it all away often since it provides the perfect breeding ground for slugs. Check regularly under rocks to ensure there are no slugs hiding underneath. Other reasons slug and snail population may boom in your lawn include:

  1. Little to no potential predators. For example, there might not be sufficient bird access
  2. Mild winters
  3. Growing plants particularly attractive to slugs such as
    1. Basil
    1. Dahlia (flower)
    1. Spinach
    1. Radishes
    1. Delphiniums
    1. Lettuce
    1. Cabbage and other similar plants
  4. Smog
  5. Chemical pesticides. This is because chemicals may end up killing off potential preys such as beetles, ladybugs, horn flies, dragonflies, and more

Slug Prevention Tips

A backyard with hanging baskets and raised gardens
A backyard with hanging baskets and raised gardens

To prevent slugs or snails, the first thing you can do, as mentioned above, is to:

  • Maintain your lawn as much as possible
  • Trim hedges and keep grass cut
  • If you store firewood, pile it away from the lawn in a non-humid area
  • Planters and pots must be placed on racks
  • If a large stone in your garden doesn’t make sense, get rid of it
  • Abstain from throwing organic waste too close to the garden
  • Keep exterior doors closed
  • Don’t overwater your lawn
  • Air the topsoil as often as you can

Slugs tend to bury themselves when they feel that the weather is about to turn colder. When that happens, it could be the perfect chance for you to remove them, since you’ll be catching them off-guard. Remember, most slugs sleeping through the winter are of reproductive age. The moment they wake up, they will lay eggs and therefore present a risk of infestation.

You can disturb the dirt as much as you want at this point and you won’t be waking up these critters, so pick them off one-by-one. You will need a hoe to dig deep enough (about 2-5 inches) and a pair of gloves to avoid touching them directly.

Pick them off one by one. Once done, use bait around the garden (such as fresh or dried spinach or beer). Continue this throughout the next season and keep on killing or throwing away any slugs you find. By winter season next year, you will have cleared all existing slugs and eggs that may have been laid during the winter season.

Double-check, though, by turning your topsoil and checking for slugs again.

Another very effective method that you can adopt when it comes to slug prevention is known as salt treatment. We mentioned above that if a slug’s skin dries up, they shrivel up and die – and what better to dry something up than salt?

We recommend using a lawn spreader to spread an even, thin layer of salt over your lawn. Remember too much salt may end up damaging your plants as well. Make sure you don’t sprinkle any salt on the sidewalk or walkway.

You may have to repeat the process one or two more times to completely eradicate slugs. We would like to point out here that salt treatment doesn’t just kill slugs but also kills off earthworms, which have been proven to be beneficial for your plants.  

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About Charlie D Paige

Charlie is a massive DIY fan, with dozens of DIY projects under his belt - ranging from tiling to electrics, and concrete pads to walls. Charlie loves tinkering, seeing how things works, the outdoors and playing with power tools... so is it any wonder that he's completed so many DIY jobs over the years?

Charlie loves spreading his hard-won DIY experience with the world via this blog.