Monday, September 27, 2010

One year of slug experience - what works, and what doesn't, at least in my garden (including lists of slug resistant plants)

I wrote a post on slugs last year after planting lupins as green manure and watching them get devoured overnight by slugs. This inspired me to do some research on slug management, the result of which was I didn't want to use slug pellets and also didn't want to ruin my karma by constantly slaughtering the creatures. I also found some great books and websites on the subject of slug-resistant plants.

So where am I a year later? First off, we have a really bad slug problem. Our garden is on the edge of a Rhine flood plain and large nature reserve on the one side, and on the other are dozens of other allotments in our garden colony. It truly seemed like a hopeless battle. My main strategy was to plant only slug-resistant flowers and vegetables. After consulting many sources, here are my lists with my personal experience.

  • chives
  • garlic chives
  • lavender
  • lemon balm
  • lemon thyme
  • lovage
  • oregano
  • peppermint 
  • rosemary
  • stevia
  • St.-Johns-wort
  • thyme 
  • valerian
    These all worked pretty well and were mostly avoided by slugs. Exceptions: the stevia was almost annihilated, and the lemon thyme (Thymus citriodorus) was devoured overnight. The peppermint was attacked but survived, but I planted some on our roof deck just to be sure. The stevia I managed to save by putting a snail collar on it - see below, but I gave up on the lemon thyme. Didn't even try parsley or sage.
    • cucumbers
    • garlic
    • lamb's lettuce
    • leaf lettuce
    • leeks
    • onions
    • rocket
    • tomatoes
    • zucchini - I raised the plants from seeds indoors until they were quite large.
    The only one of these that was notably attacked were the cucumbers, which were also fine after I put a snail collar on them. Here, too, there were many things I didn't dare try, like cabbage, broccoli, kohlrabi, etc.

    Perennials - negative list
    I inherited many perennials from my predecessors in the allotment, but also planted some myself. Here are some that were incessantly attacked by slugs to the point that they just looked terrible, despite the fact that some of them are listed by some sources as being slug-resistant:
    • all of the at least five types of hostas I had
    • Centaurea montana (perennial cornflowers)
    • salvia of various kinds
    • lobelia of various kinds
    • Echinacea of various kinds (coneflowers)
    • marguerites
    • hydrangeas
    • asters
    • clematis
    Although these flowers survived and even bloomed, I've now thrown them almost all out because I can't bear the way they look after slug attacks.

    Perennials - positive list
    These flowers weren't touched by slugs:
    • dame's rocket (Hesperis matronalis)
    • forget-me-not (Myosotis)
    • hellebore
    • hardy geraniums
    • astilbe
    • lady's mantle
    • roses
    • bleeding heart (Lamprocapnos spectabilis)
    • columbine (Aquilegia)
    • day lilies
    • irises
    • common bugle (Ajuga reptans)
    • alum root (Heuchera micrantha)
    • saxifraga of various kinds
    • sedum of various kinds
    Annuals - negative list
    • violas - forget it!
    • petunias - I planted some in hanging baskets two meters off the ground and still found slugs in them, god knows how they got there.
    • lantana - Wouldn't you think that these prickly, strong-smelling plants would repel slugs - hah!
    • sunflowers - By installing snail collars until they were about a meter high I managed to raise amazing sunflowers, but they are definitely beloved of slugs when young.
    •  zinnias - Gave up and had them only on the roof deck, where they did beautifully:

    Annuals - positive list
    These flowers weren't touched by slugs:
    • moss roses (Portulaca grandiflora)
    • pelargonium geraniums
    • impatiens (Impatiens neuguinea)
    • nasturtium (Tropaeolum majus)
    I also purchased a seed mixture of annuals resistant to slugs called (in German) "Sperli's Schleich Dich Blühende Schneckenbarriere".
    This was a fabulous buy and produced many lovely flowers that were not touched by the slugs. Unfortunately, the package does not list what kinds of seeds it contains. I identified the following:
    • love-in-a-mist (Nigella damascena), both blue and white
    • some kind of rudbeckia
    • some kind of snapdragon
    I've already purchased another package for next year. Maybe someone can identify the flowers in this mixture more precisely? In the first shot below are what I think are some kind of annual rudbeckia, and in the second shot you can see the lovely seed pods of love-in-the-mist below the rudbeckia, and in the background you can make out the pale blue of still blooming love-in-the-mist. In the lower part of the photo is what I believe to be snapdragons (click to enlarge).
    I tried a few other methods of discouraging or getting rid of slugs, and found the following to be ineffective: coffee grounds, watering with moss brew, and beer traps. I also broke down and tried environmentally-friendly ferramol snail pellets. Both beer traps and pellets killed a few, but they were followed immediately by legions more. The only manual method that made a difference was simply gathering them up by the dozens (or hundreds!) at dusk and killing them, not a fun activity.
    So my resume: 1) Be more consistent about only growing slug-resistant plants, and 2) snail collars work on plants with the right shape and size.

    How about the rest of you?


      1. It is rough dealing with slugs for sure. I feel for you as they must be about as bad as rabbits and deer. Here we have a few but they don't usually cause major damage. When they do I use my slug pellets that I bought in Germany like 10 years ago! I can't believe I still have it! Honestly. But normally I don't bother with the things. They mostly come on my porch when it is wet and eat the cat food. In that case a good dose of salt fixes them. Sounds awful I know but so far they live well with little interference from me. Good luck with yours! You are most smart to plant resistant plants.

      2. Tina, next time I curse the slugs I'll try to be grateful for the fact that we don't have a deer or rabbit problem, although deer and rabbit abound in the area, so I've often wondered why. I also can't believe you still have your German pellets!

      3. Did you try natural granite based rain-resistant granules we bought some but haven't used them yet. They are a barrier method so you pop them around susceptible plants.

      4. For me, not using a lot of water obviously helps. But I also think slugs don't like the sharp needles of the redwood twigs that rain down into most of my garden on a fairly regular basis. And Sluggo seemed to help as well. I used that when seedlings were under attack.

        What a pain, though...And I wish I could get some ducks to visit, they love slugs...

      5. Fascinating, useful and interesting post.

        I have sage - slugs don't touch it. They leave calendula and geraniums alone too. Asters, Asiatic lilies - scrumptious feast for slugs and they disappear overnight. Ditto lily of the valley. Squash and tomatoes - they are fine. (Tomatoes probably wouldn't be if I were to plant them out when tender but I wait till the stems are thick and tough.) Lupins - slugs love 'em! No point in putting them out in their first year. Parsley - gone in an instant. Chives - alright when tough and established but eaten almost to the ground when little. Seems able to recover though and send up new shoots.

        I collect slugs and snails and take them to open ground far enough from the house that they don't come back. Couldn't kill them. (Not necessarily a virtue - but . . . )

        Thanks for faving my blog on Blotanical.


      6. Dear Barbara, This is an excellent posting ... very useful! I stopped growing cantaloupe because slugs always devoured them. I handpick the slugs and drop them into a dish of salt to kill them. I will share your slug-resistent plant list with the participants of a gardening class I teach, if you don't mind. Pam x

      7. Pam, I'd be honored if you used my list for your class. One thing I have learned, though, is that not everyone has the same experiences with the same plants. Maybe there are regional differences in slug species, other available foods, whatever.

        Esther, thanks for your input. I'm glad to hear squash and sage work for you, and I must try calendula. I read an interesting study on the homing instinct of slugs - so don't be too sure about the ones you have released in the wild.

        Town Mouse, I have no choice about water - it falls constantly from the heavens here. I've also read that pine needles and even pine cones repel snails/slugs. I'm also hoping for a visit by migrating ducks.

        Green Lane Allotments, I don't know about granite granules, and will look into them, thanks.

      8. Dear Barbara, I do agree that if one has a very bad problem with slugs in the garden, the best thing to do is to seek out slug resistant plants since one can never hope to eradicate them.

        In my own garden, J, my gardener/handyman puts a collar of ash around the necks of vulnerable plants, such as Hostas, and this does work. However, slugs are not major pests for me.

      9. It seems as though there has to be some nasty pest that wants to devour our gardens. You get the slugs, I get the voles and the chippymunks. It is good to find out what works and what doesn't and then you feel pretty happy that at LEAST a few things are resistant!

        I am glad those painter/repair people did not crush your garden. My husband tries very hard to not step on stuff when he works on the house.

      10. Edith, I haven't tried ash yet, maybe it's worth a try.

        Rosey, maybe you're right and it's just our cross to bear as gardeners. I have voles, too, but compared to the slugs they seem harmless.

      11. Interesting post Barbara. Here we're fortunate that the typical garden-variety slugs seem quite scarce. We do have a native banana slug, but thus far, they seem to be more interested in our woodland plants than the cultivated gardens.

        Our first house though suffered from slugs tremendously, especially during the late winter/early spring. My husband kept trying to grow hops, which apparently to slugs are akin to caviar. We finally tried, out of desperation, some copper sticky tape around the base of the hop shoots. Apparently the slugs experience an unpleasant charge from the metallic copper when they slither on it. It worked well enough, that the shoots finally were able to grow, and we had a fabulous hop harvest. I don't know if copper tape is available at your garden centers, but when little else worked for us, it helped a lot!

      12. Clare, I've also read about copper wire or strips, and it's available here, too. I've been wanting to try hops in my herb garden, and am a little discouraged to hear that it is susceptible to slugs. Maybe I'll try it with copper since it worked for you.

      13. We've used copper tape around the pots that we grow our hostas in which works until the leaves grow and touch other plants - then the slugs abseil across.

        As for seedlings we built a sort of moat in our cold frame. WE filled a tray with water set upside down pots in the water and placed seeds trays on seedlings on top of the pots - the slugs/snails would have to learn to swim to cross the moat - it worked!

      14. Barbara, I remember how terrible the snails were in Germany. Not good for a gardener, that's for certain. You've done a wonderful job cataloging your successful vs. unsuccessful plants. I was going to suggest the beer traps, but I see you've tried those. Agreed, the best bet is to plant only those species distastful to slugs. Admittedly, I'm surprised about the Lantana. I would think it to be a hinderance as well. hmmm!

      15. After reading about your battles with slugs and the list of casualties, I am very tempted to get a small flock of ducks. The pellets didn't work well this summer. With all the rain we had, the population seemed to explode no matter how many applications of Sluggo I made. I have since given up, or in other words, not looked at the garden areas with hosta plantings.

        Christine in Alaska

      16. Hi Barbara,
        This is a wonderful, informative post! I was suprised by some of the things that didn't cope well - particularly the lemon thyme and lobelia! Seeing violas listed there helped confirm my own suspicions about what has been happening to some of my little violas. Mind you, it is the first year the have ever been eaten, so I'm finding that strange.
        I'm fortunate to have a couple of free ranging ducks which is a great help...but we still get some slugs and snails, mostly on pot plants!
        By the way, those beautiful zinnias have inspired me to try some!

      17. Barbara, such great research, sounds like the slugs are horrible in Germany. Mine, not that bad, yay, (of course, now I have cursed myself to legions crawling in). I do have a lot of wood ashes that I put around the hostas, they seem most attracted to them.

      18. Barbara, Where would we be without hardy geraniums and daylilies in our gardens? These plants are tough, beautiful, and are bothered by very few pests. Thank goodness! -Jean

      19. Jean, you're right, and I'm very grateful for the hardy plants that don't need a lot of attention.

        Deborah, hostas just look so awful after slug attacks I ripped all of mine out in frustration.

        Gippslandgardener, thanks for you kind words. Lobelia was on a list of slug-resistant plants I found - but our slugs didn't know that. I grew my zinnias from seed and it was pretty easy. The variety was "Lollipop Zinnia" if I remember correctly.

        Christine, I think pellets work with plants that need to be protected temporarily while young. But there's just no way to permanently keep slugs off of hostas.

        Kimberly, the lantana surprised me, too. There doesn't seem to be rhyme nor reason as to what slugs like. They don't touch the delicate young leaves of columbine or astilbe - go figure.

        Green Lane Allotments, I *love* the idea of a moat! Must try that. And abseiling is what the slugs in my hanging pots must have done. LOL.

      20. Hi there, I thought you might be interested in my ongoing slug research. Sounds as if your slug problems might rival mine! I'll be continuing experiments until I find the very best remedy.

      21. Oh, and slugs really like my tomatoes. Grrr....

      22. Great post! Our slug are back again. Argh. I want ducks! Luckily they aren't yet doing too much damage and I'm trialing some barrier methods. Ugh.

      23. Ducks, ducks, ducks!! My Welsh Harlequins and Khaki Campbells do a good job. I haven't had any luck with leaf lettuces; it just seems like I'm feeding the slugs.

      24. Ducks, ducks, ducks!! My Welsh Harlequins and Khaki Campbells do a good job. I haven't had any luck with leaf lettuces; it just seems like I'm feeding the slugs.