All gardeners in Britain have problems with slugs and snails. Here on Skye, because the soil has little lime, the snails are quite small and less of a problem, but the slugs can be massive! The weather is almost constantly damp – Skye is not called the Misty Isle for no good reason! The slugs are particularly a problem with seedlings, and new transplants. The former being young and juicy and the latter somehow more attractive in the stress of establishing themselves. I also find new growth of some perennials always munched – I’ve never dared trying Hosta for that reason (although they are on my list of interesting edibles perennials to try). I am going to describe here an experiment I ran a few years ago to evaluate possible slug protection schemes for young plants. There were only three things I tried, all barrier methods.
1) A substantial ring of eggshells.
The theory is either the dryness or the sharpness of the egg shells are uncomfortable for the slugs. It happened that I had been saving my egg shells for some time so had a largish quantity of broken shells that had been oven dried.
2) A copper barrier.
Either the ‘taste’ of the copper or possibly an electric shock from some sort of battery effect are supposed to stop the slugs in their tracks. I had found in my previous garden in Solihull that the only way to keep my seedlings safe was to have them on a scaffolding frame table, so I was quite hopeful of this – the copper I used in the form of readily available (if a bit expensive) adhesive tape, stuck to the rim of a cut down large diameter plastic plant pot. This was then pushed a little into the soil around the vulnerable plant so that there were no gaps for the slugs to crawl through, and the wind was less likely to blow it out. I guess the collars were about 2 and a half inches tall and pushed in by about an inch.
3) A physical barrier or wall.
This barrier was the same cut down plant pots as above, but without the tape.
The victims or sacrificial plants I used were lupins (I had bought the seed as tree lupin but that’s another story!) I had a quantity of these ready to plant out and previous experience had suggested that they are delicious to slugs. I planted out the plants in two different areas of the garden – some in my ‘dog resistant garden’ (our elder dog Douglas liked to help with the gardening when he was younger), the others in the fruit garden which had been mulched with cardboard. The dog resistant garden is quite shady, so both areas were pretty much slug heaven. Different plants had different slug treatments in both areas.
The results were both interesting and not quite what I was expecting. The eggshell barrier turned out to be pretty useless. Less than three weeks later none of these transplants survived. The plants with collars faired much better; most of these seedlings had no damage at three weeks. Interestingly the copper tape did not seem to add a great deal more to the effectiveness of the plant pot collars. Even at about 6 weeks the transplants with collars were doing well. The main issues appear to be bridging the collar with leaves and sticks, or them being displaced by excited cats etc.
At 6 weeks it is amazing how the chickweed within the collars are growing away, whilst there is no sign of these weeds in the unprotected areas! The lupins in the fruit garden didn’t do so well in the longer term – I had planted them amongst comfrey, which I use as a living mulch amongst the fruit bushes. Unfortunately these proceded to mulch and smother most of the lupins as well!
In conclusion: a barrier of a cut down plant pot collar with or without copper tape can be a quick, cheap and effective means of protection for vulnerable plants. I now almost routinely plant out new transplants with a collar. It also makes them easier to spot in the garden. The results are not 100% effective, but do make a significant difference.