I have been thinking about how best to deal with imported brown garden snails in the garden. I was out early this morning, and I found one medium-sized one and maybe a dozen tiny ones in my small front garden. I pay special attention to which plants they are climbing. And I also pay attention to which plants they eschew. (That is, they don't chew.)
If I plant a dahlia, any snails in the vicinity are all over it right away. But they aren't at all interested in Mexican sage (Salvia leucantha), feverfew (Tanacetum parthenium), or Jupiter's beard (Centranthus ruber). They never touch my California fuchsia, which is blooming like crazy in the garden right now, or the matilija poppy, the California poppy, or the blue-eyed grass. They aren't interested in the leaves of Pacific coast iris, but will eat the flowers. I planted Oenothera odorata, and they do not like it, but they do like the flowers of gazania.
This morning, I found all of the little snails on the stems and flowers of an Erysimum 'Apricot Twist'. I found the bigger one on Gazania. Duly noted, though, the erysimum has been blooming all summer and hasn't attracted many snails before this.
In zoos, in the areas where vegetarian animals are living, they have to plant things they won't eat. Otherwise, the animals would simply eat up the plants right away, and the results would look depressing and ugly to the human zoo goers. So zoo landscapers are forced to put the animals in compounds with plants that look like they are from the right habitat, but which the animals actually rather detest. (But before you feel sorry for them, remember they get fed stuff they like. So, for example, the Koalas get branches of fresh eucalyptus leaves brought to them as needed.)
Taking a clue from the zoo (the landscaping, not the feeding part) we can plant a garden that snails don't much like. It is already done to avoid deer damage, but many gardeners just keep planting anything they like in gardens where they haven't planned to put much energy into eliminating snails, and are then surprised when snails eat plants up.
So that is part of the equation. If you don't plan to meticulously control snails, don't plant their favorite food. Another important part is that if you do plant something they will eat, snail bait alone is unlikely to be adequate to eliminate snails from a garden. You probably will have to remove some of them by hand. They are, after all, are slow-moving creatures. And in the daytime, they don't usually move at all. They have predictable daytime hiding places where they generally sit quietly. So why not remove them? They hide in places that are rather dry, dark, and have a smooth surface to cling to. Once you find their favorite daytime hiding places, you will find that there are usually some there (as long as there are any left in your garden.) And night or early morning hunts find them right out in the open, and also show you which plants they really like.
When you have taken a snail out of your garden (or returned it to the soil as fertilizer) you have stopped its damage. I can't see why anyone wouldn't want to do this before, and as an adjunct to, beer traps, Sluggo bait, or any other method that depends on the snail finding what you left for it and preferring it to your plants. There has to be a lag time, during which the snail is eating a garden plant. (Bothers me to lie awake wondering if the snails found my new viola transplants first or the snail bait I left in the garden.)
Anyway, that's why these two steps are first on my snail damage prevention "to do list:"
--watch what they eat. Don't plant favorites where you can't protect them.
--hand pick as much as possible. They have slow life cycles. You really can make a big difference with just a few hunts.
Pardon me, I think I will take a flashlight now and try to get a few more of the small ones, from last summer's hatch, before they find my violas...