Slugs and snails are not pests you would normally expect to find lurking among your houseplants. When they do appear indoors, they have usually hitched a ride in with a new plant, hidden in compost or spent some time outside before coming back indoors. While they are unusual houseplant pests, they can cause surprisingly noticeable damage, particularly to soft new growth, which can be nibbled down almost overnight.
The good news is that slugs and snails are much easier to spot and remove than many of the tiny pests that plague houseplants. They tend to hide during the day and come out when conditions are cool and damp, so knowing where and when to look is half the battle. In this guide, our Horti team explains how to spot the signs, find where these slimy stowaways are hiding and get rid of them before they make another meal of your plant.
How to Identify Slug and Snail Damage
What the Damage Looks Like
Slugs feed at night and in damp conditions, rasping away plant tissue with a file-like mouthpart called a radula.
They thrive in the cool, humid conditions that also suit many houseplants, which is why conservatories, terrariums and plants summered outdoors are the usual trouble spots. If you keep part of our terrarium plants range in an enclosed setup, a stray snail can breed quietly in the constant humidity.
Look for irregular holes chewed through leaves, ragged leaf edges, and whole seedlings or soft shoots eaten to the stem. Damage on tougher, older leaves is less common; slugs and snails prefer tender new growth and thin foliage.
The giveaway is the slime. Dried mucus leaves a silvery, slightly iridescent trail across leaves, pots and nearby surfaces. If you see holes plus silver trails, you are almost certainly dealing with molluscs rather than caterpillars or beetles.
Where to Look
Search after dark with a torch, when they are active. During the day, check the cool, dark, damp hiding places: under the pot rim, beneath the pot itself, in the drainage tray, under leaf litter on the soil surface, and tucked into the crown of the plant. In terrariums, lift hardscape and check leaf undersides.
Where Do They Come From?
The three common entry points are new plants brought home, bagged compost that was stored somewhere damp, and plants that spent summer outside. Eggs are small, round and pearly, laid in clusters in moist compost, so a plant can arrive apparently clean and produce slugs weeks later. This is one more reason we always suggest a short quarantine, as covered in our guide on whether to quarantine new houseplants.
How to Get Rid of Slugs and Snails on Houseplants
Immediate Steps
Start by picking them off. Because they are large and slow, hand removal after dark is genuinely the most effective single method. Drop what you find into soapy water. Move the affected plant away from others while you deal with it, and clear away any leaf litter or debris on the soil surface that gives them cover.
Trapping
Slugs and snails are easy to trap. A shallow dish of beer sunk to soil level draws them in overnight. A piece of damp cardboard or a hollowed citrus half left on the compost gives them a daytime hiding spot you can lift and clear each morning. Repeat for several nights and you will usually clear a small infestation completely.
Reducing the Damp They Rely On
Let the compost surface dry more between waterings, since constant surface moisture is what keeps them active. Water in the morning rather than the evening so the surface is drier overnight. Bottom watering helps here, as it keeps the top of the compost drier while still hydrating the roots. A free-draining mix from our houseplant substrates range makes this easier to manage.
If the Problem Persists
For stubborn cases, wildlife-safe ferric phosphate slug pellets used sparingly on the compost surface will deal with what hand removal misses. Keep any pellets well out of reach of pets and children. Our pest control range and the wider plant care selection cover the products worth keeping on hand.
Preventing Slugs and Snails
Prevention comes down to three habits. Quarantine new arrivals for a couple of weeks and inspect the soil surface and pot base before they join your collection. Check plants thoroughly before bringing them back indoors at the end of summer, including under the pot and around the drainage holes. And store spare compost sealed and dry rather than in an open bag in a damp shed or greenhouse.
Keep an eye on any plants in permanently humid setups, since these are where a small population can build unnoticed. A quick torch-lit check every week or two is enough to catch trouble early.