I was always taught that snails were plant pests, creatures to be crushed on sight. It took me decades of gardening to realize that something was wrong with that belief.
I kept seeing snails on my garden plants, but where was the chewed up foliage I was expecting? The more I looked, the more I realized they seem to be sliding over my plants without doing any damage at all. So I did some research… and was surprised (in fact, shocked!) to realize I’d actually been decimating a friend of my garden!
The most common garden snail in North America is the banded snail (Cepaea spp.). The common name actually covers two species that are practically indistinguishable: the grove snail (C. nemoralis) and the white-lipped snail (C. hortensis). Both are brightly colored with shells that may be plain yellow or yellow with brown spiraling stripes. They were originally native to Europe, but were introduced to North America long ago, as back as far as the beginnings of European colonization in some areas.
The interesting thing to note about banded snails is that they rarely eat living plants. Instead, they’re more like Mother Nature’s vacuum cleaner. They feast on dead and dying leaves, fungi, algae, moss, and insects like thrips and aphids. If you find them sliding over the leaves of your plants, it’s because they’re actually helping you out by cleaning the leaves of fungi and algae. Who knew!
I’m not saying they never eat greenery. They’re said to love nettles, for example… but nettles are weeds, so do you really care? In my extensive garden tests (yes, I’m one of those plant nuts who has one of everything), I’ve found them eating exactly one plant: Allium ‘Mount Everest’, a white-flowered ornamental allium. Oddly, I grow almost 30 different kinds of alliums in my garden, both ornamental and edible (garlic, chives, onions, leeks, Welsh onions, etc.) and only ‘Mount Everest’ seems to interest them.
In actual fact, most North American terrestrial snails are fairly innocuous, if not out-and-out harmless. One major exception would be another European import, the brown garden snail (Cornu asperum, formerly Helix aspersa). This is the well-known edible snail of escargot fame, but also a formidable plant-eater. Where it has been introduced (notably California, where it was imported in the 1850s for use as food), it will be indeed cause considerable problems to a wide range of garden plants. But then, there is no way you could possibly confuse this large brown snail with its smaller yellow or yellow and brown cousins, the banded snails, so perhaps, if both types of snail abound in your area, you might want to do a bit of “selective pruning” and remove the brown ones only.
But Slugs are Not Your Friends
I’m always surprised that so many people confuse slugs and snails. Yes, both are gastropods (a group of mollusks) and move about on a muscular “foot”, both have two tentacles with eyes on the tips… and both leave slime trails on our plants. But snails have spiral shells and slugs, no shell at all. So, to me, they are as different as a stork would be from a sparrow. But apparently not to everyone. Visitors to my garden often comment on how many “slugs” I have, because those bright yellow banded snails stick out like a sore thumb and are often plastered on shrubs and walls, right out in open. Of course, visitors will not actually be seeing true slugs, as they hide during the day. I take advantage of the comment to explain the difference and tell them how I’ve learned to love my snail population.
And the truth is that true slugs, the shell-less gastropods, are almost always bad news. Yes, there are predatory slugs, even slugs that eat other slugs, but for the most part, slugs are just as fond of live greens as dead and dying leaves, if not more so, and cause considerable damage to our gardens. The most common and most damage-causing species in North America is the grey field slug (Deroceras reticulatum), which is pretty much ubiquitous now, although it too was originally introduced from Europe.
So, the rule is: don’t hesitate to control slugs (here are a few suggestions as to how to do so), but leave those banded snails alone!