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How can I stop slugs damaging my plants?

Your gardening questions answered: My garden is suffering very badly from snail and slug damage

Organically acceptable slug pellets will help to keep slug attacks at bay but are less effective during periods of heavy rain.

Fionnuala Fallon
Mon Apr 22 2024 - 04:00

Q: My garden is suffering very badly from snail and slug damage this spring after all the wet weather. Are there any plants that they don’t like to eat that you could recommend?

A: There’s no doubt that it’s been a truly terrible year for slug and snail damage, a result of so many months of heavy rain as well as the higher-than-average winter temperatures that together suit them so well. April-May is also always a very challenging pressure point in the growing year for damage, with the tender young growth of many seedlings and herbaceous perennials emerging from the ground just as slugs and snails are at their most active in terms of their breeding cycles. But if you can get plants and seedlings through this vulnerable phase, then they’ll typically become far more resilient as the season advances.

Organically acceptable slug pellets will help to keep slug attacks at bay but are less effective during periods of heavy rain as well as expensive to use on a wide scale. They’re also not recommended for very regular use as the iron they contain can discourage earthworm activity. Nematode control used to be another reliable option that organic gardeners could avail of but unfortunately hasn’t been available for several years, both for technical reasons as well as because of Brexit.

Encouraging a range of habitats to attract their natural predators (birds, hedgehogs, frogs, ground beetles) will also help. So will homemade nettle feed, as will beer traps, although these need to be replenished regularly in wet weather.

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This year I’m also going to try using a homemade garlic spray on the recommendation of a gardening friend who swears by it. He pops garlic cloves into a lidded bucket of water and then applies the liquid every couple of weeks to vulnerable plants as a diluted foliar feed, using a watering can.

Other measures are less reliable. My own experience of using physical barriers including crushed eggshells, sharp horticultural grit, used coffee grinds, wool pellets and copper tape suggests that none of them are usefully effective. The researchers behind the RHS Gastropod Barriers project came to similar conclusions, recommending that the most effective method of organic control is a combination of night-time handpicking and then dispatching/disposing of the offenders along with practising good garden hygiene.

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Ornamental perennial species that are especially vulnerable to slug and snail attack include hosta, delphinium, echinacea, dahlia, ligularia and lobelia. If you’re determined to grow any of these, then you’ll need to take especially good care of the plants, especially as they emerge from the ground when they’re at their most tasty and succulent. Shrubs are generally much more resilient, but some species are vulnerable when they’re very young including magnolia.

Thankfully the list of species that are almost immune to attack is far longer. It includes perennial geraniums, linaria, phlox, many forms of scabious, veronica, penstemon, astrantia, aquilegia, alliums, geum and euphorbia.

Most problematic is the issue of protecting young seedlings, which are notoriously attractive to slugs and snails. Along with the combination of the measures recommended above, I’d suggest raising these from seed in pots/cell trays and then transplanting them out as sturdy young transplants that can — with some tender care — tolerate a certain amount of damage. This technique is very useful for many kinds of plants, especially flowering annuals and vegetables such as lettuce, members of the brassica family, courgettes, beans and peas.

Fionnuala Fallon

Fionnuala Fallon

Fionnuala Fallon is an Irish Times contributor specialising in gardening

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