SLUGS - CAN WE LEARN TO LIVE WITH THEM?
Yes, I know its a bad year, but they have an important role in the garden - we don't want to obliterate them all, so how can we live with them and love their role in the garden?
So has my opening image got you squirming or intrigued? Did you know that slugs can get quite so large?
Yes, its taken in my garden in Somerset and not a rainforest in Costa Rica. Is it a friend or foe? Have you guessed yet? Read on to find out more.
A warm wet winter
This winter has caused problems for lot of our plants and some of our animal life, but there’s one group that’s thrived - slugs and snails. I don’t know about your growing space, but there are slugs, snails and clusters of eggs under everything in my garden. It doesn’t bode well for the growing season ahead, and I am very wary of planting and veg out at the moment!
So, this week my focus is on what we can do in the garden or allotment to cope with the mollusc invasion. I’m not looking to wipe them out, as they have a critical role to play in food chains and decomposition, but I do want a bit more control around the veg beds and balance in the garden ecosystem.
We have to remember that while the average slug can eat 40 times its weight in a year, only a small proportion of this is living plant material. They eat mostly decaying leaves, damaged fruits and anything that goes on the compost. They will also eat animal droppings and even dead bodies, which is really useful!
Lots of different types of slugs
Some slugs are more destructive than others. You may not like the look of the large black slug, but that's not as damaging as other types, because it prefers rotting plant material and dead bodies rather than your precious plants. The ones to watch out for are the underground species, such as the keeled slug with its distinctive ridge running down the middle of its grey-brown or black body.
Now - back to the opening image. I think this is a fabulous creature and I was delighted to find it in my garden. It’s the leopard slug or great grey slug (Limax maximus. I was so thrilled to find it. It’s nocturnal and believe it or not, it usually returns to the same hideaway every night.
Why do I want more of these beasties? They are omnivores – so have a mixed diet that comprises mostly of dead plants,so it’s a detritivore too, but it’s also known to attack small slugs that venture close, so it does offer the gardener a protection service!!! So please welcome these beasties into your garden.
Slug life
Slugs are toothless, feeding with their rasping tongue or radula, and its rather like a piece of sandpaper. They hide in shady places during the day, often under flower pots, stones, bits of wood, long grass, etc and emerge on humid nights to feed and they can range a surprisingly long way as you can see from the glistening mucus trails along the ground. They lay their round, white eggs in clusters under rocks, in decaying wood, down the sides of raised beds etc, all places where they are out of sight and safe from predators.
Here are my top tips for making your growing space less slug friendly
· Think about the type of compost / mulch you use as slugs prefer a bacterial-based compost, so mulch of hay or grass clippings will attract slugs, but a straw mulch is less to their liking, hence a mulch like Strulch (mineralised straw) is said to deter slugs and snails.
· You get less damage in diverse systems. Slugs tend to eat less overall, when they have to keep switching to different plants, whereas when they find a large area of a single crop they can feed more effectively, so polyculture is better.
· Remove their hiding places and keep your pots off the ground on footers. They love rotting wood. One of the downsides of using wood planks to make raised beds is that the wood starts rotting, creating the perfect hiding places for slugs and snails. They like long grass too. If like me, you encourage wildlife by leaving fallen leaves on the ground and building log piles etc, you end up providing the ideal places for slugs as well as the predators, so I try to place these features as far away from my veg beds as possible.
· Some plants are said to act as a deterrent - Astrantia, wormwood, rue, fennel, mint and rosemary are believed to give off a scent that repels slugs – but I’m not sure ….
· Encourage natural predators in the garden, such as blackbirds, starlings, frogs and toads, slowworms, hedgehogs, ground beetles, centipedes, rove beetles etc. This can be achieved with providing trees, shrubs, nesting site, ground cover and water etc.
· Move the compost heap (where you want slugs and snails) away from your growing areas
· Cut low hanging branches that drag on the ground where they create dark damp hiding places
· Keep grass low near your vegetable beds and vulnerable plants as slugs hide in long grass during the day
· Hoeing creates a friable surface that creates a rough surface is doesn’t appeal to a slug
· Plant out transplants when they are older and better able to overcome any damage. If they have a larger leaf surface, any slug damage will have less of an impact and the plant has a chance of recovery. Avoid too much nitrogen fertiliser as this encourages lush susceptible growth.
· Make sure you harden off vulnerable plants that have been raised in a greenhouse or polytunnel. Moving them into a cold frame before planting out will thicken the leaves so they are less susceptible.
· Delay sowing vulnerable crops, such as carrots, when the weather is cold and wet. You want the seedlings to germinate and get away quickly, so a period of cool weather will slow them down and make them vulnerable to slugs.
· Don’t plant vulnerable crops in blocks but mix them up with crops that slugs don’t like or plant a barrier of nasturtium. You can do the same with ornamentals, slugs and snails tend not to like grey foliage, downy waxy or waxy leaves, thorny leaves etc.
· Another simple and effect control is watering in the morning, so the soil dries out before the slugs and snail are active. This has been found to reduce damage considerably.
· Use brambles to stop the slugs and snails from sliding over the soil surface. Cut short lengths and stack to create a little fence which makes it more difficult the slugs to move across. I have tried this around some of my larger veg transplants and sunflowers successfully.
· If you suffer slug damage on potatoes, choose for varieties that are less susceptible
Controlling slugs
There are loads of ideas on how to control slugs, some more dubious than others. I don’t think any one is the answer, rather it's a combination of methods to keep the numbers at an acceptable level.
A few years ago, the RHS did study on 5 popular methods of controlling slugs and snails: copper tape, sharp grit, pine bark, wool pellets and egg shells. Lettuce was grown in pots and raised beds for 6 weeks, protected by the different treatments, then harvested and examined. Plants in the ground were more susceptible to slug and snail damage than those in pots. But none of the treatments warded off slugs and snails. It was concluded that the molluscs had such thick mucus covering their foot that they were unaffected by the different surfaces, although they would prefer a moist, organic mulch than a dry, gritty one. I think one of the best methods is going out at night to collect them and move them somewhere they will prefer, like the compost heap.
Nemaslug
I I have found Nemaslug to be very effective. It’s a biological control method using the nematode Phasmarhabditis californica which infects all common species of small to medium sized slugs. The pouches contain infective nematode juveniles in a powder carrier which when mixed with water, creates a suspension that is applied as a drench using a watering can with a coarse rose. When the nematodes find a slug they enter its through their breathing pore and once inside, they reproduce and release bacteria and it is the bacteria that kill the slugs within a few days. The nematodes then leave the dead body and move through the soil to find new hosts.
For the treatment to be successful, the ground temperature must be above 5C, even at night and the soil must be moist. You may have to water the soil to keep it moist and allow the nematodes to thrive. It takes several days for the nematodes to become active and several weeks for their effects to be detected. But often you don’t see anything as there are no dead bodies lying on the soil surface!
It is expensive and needs to be applied several times through the growing season, but if you use this treatment over a number of years, the numbers of slugs and snails will decrease. Its not a treatment I would use across the whole garden, instead to use it on specific veg beds where I think there will be a problem. Don’t forget, soil temperatures need to be above 5C, so I think we are OK now to start applying it.
Find out more
This newsletteris just a summary of the section slugs and snails in my latest book, The Resilient Garden and Allotment Handbook There you will find a comprehensive section on slugs and snails where I look at the different methods of controlling them, and their effectiveness or not, plus a chapter on biocontrols.
It publishes next week and costs £15 which I think represents good value for money especially since it’s printed in the UK on sustainable papers as well.
'A must-read for anyone who wants to know how to grow their own zero-food miles, pesticide-free veg, while treading gently upon our planet.' Dave Goulson, author of The Garden Jungle and Silent Earth
Happy Gardening
Sally
Talks and Workshops
Talk 14 March Sally is talking on the climate change garden at Wells Garden Club, in the Town Hall, Wells, Somerset
Talk 20 March Lavington Garden Club in West Lavington Village Hall, on the Healthy Vegetable Garden
Talk 21 March Malmesbury U3A - as more general talk on climate change and trees, historic gardens etc
Workshop 24 March An Introduction to growing fruit and vegetables with Sally at her garden at Empire Farm in Somerset - couple of places available
Workshop 5 April Growing polytunnel and undercover edibles over winter with Kim from her garden in West Wales
Workshop 19 April Get climate change savvy GYO course with Kim from her garden in West Wales
Talk 11 May Sally is speaking at the FarmED Literary Festival - the venue is brilliant and the speakers awesome