Protect your plants from slugs without chemical nasties
For me a garden is nothing without the wildlife that it helps sustain.
I love pretty-much every creature that makes it home in my garden: from the family of badgers who use their huge paws to helpfully rearrange rockery stones to get to worms; the delightfully disruptive squirrels who insist on checking out every bulb I plant; through to the playful foxes that steal my shoes if I forget to take them in at night
I even love the 1,000 strong flock of starlings that fledge in our trees every May only allowing us four hours sleep a night with their incessant cries for food. (read my blog on how to protect plants, lawns and bulbs while encouraging wildlife).
The one garden visitor I can do without is the slug. My shady woodland garden, with multiple dry-stone walls, is a paradise for the shell-less, terrestrial, gastropod molluscks commonly known as slugs.
I use as few chemicals in my garden as possible and that includes the metaldehyde that makes up the main ingredient of most slug repellents. Metaldehyde is poisonous for most garden wildlife, including animals such as hedgehogs who eat the slugs that have consumed this slug bait. In addition it is dangerously toxic to dogs and it's just something I don't want to risk using in the garden.
So how can you grow the hostas, delphiniums, dahlias and tulips, among many other types of plant, that make up a slug's preferred diet?
Organic slug control
We have had great success with organic slug control containing ferric phosphate (iron phosphate). As ever, there are many different opinions as to the effectiveness of slug bait based on ferric phosphate but there is unilateral agreement that it is not harmful to humans, pets or wildlife. Trials led by the RHS are due to be published soon assessing the effectiveness of all different types of slug control (including ferric phosphate) – I've put the link at the bottom of the article.
Valentine's Day Massacre
Start early! I can't remember which hosta expert gave me this advice at one of the RHS shows but it has stood us in good stead. Every Valentine's day, Sarah and I head out into the garden at night after our own celebrations and start the massacre by spreading ferric phosphate pellets around. This is especially important after a mild winter as there hasn't been enough cold to kill off the dormant slug population; this year we were already seeing slug presence around the garden in early February.
This is the ultimate “stitch in time saves nine” approach: each slug (they are hermaphrodites) - can lay up to 300 eggs a year with each baby slug capable of producing their own eggs within 3 months of hatching. You can imagine the nearly exponential growth if you let that first slug lay eggs...
Once the weather warms up we apply Nemaslug which contains the nematode species Phasmarhabditis hermaphrodita. This nematode is a specific parasite to molluscs, with no adverse effect on other types of animal. It works by entering the gastropod’s body and releasing a bacterium which stops feeding and causes a fatal disease. The slug will retreat underground and die there. You can buy Nemaslug from either Sarah Raven, Crocus or Amazon.
We have been using copper tape around the top of pots which contain slug-delicacies such as hostas and delphiniums. We check the pot each year to ensure the copper tape has not been breached (animal damage/ degrades over a period of years/ covered by foliage that provides a bridge for the slug to crawl across) and have had great success with either no slug damage or very minimal damage. Apparently slugs (& snails) avoid copper because of the reaction between the mucous produced by the slug or snail and the copper. - something like an electric shock. The same principle applies to copper rings which can be placed on the ground around plants or copper mesh fence barriers which can be placed around larger areas of planting. You can get copper tape from Crocus or Amazon.
Here's a good article which summarises experiment using copper tape as a barrier https://www.slughelp.com/copper-snails-slugs/
Another barrier method for repelling slugs that we only discovered last year is slug wool pellets (we've been using Vitax Slug Gone). The pellets are made from recycled wool and when you place them round the base of a plant and then wet them, they form a protective barrier that slugs and snails will not cross. We've spoken to other people who do not rate them but last year we used them around the base of a clump of hostas that we've always ended up having to cut down before opening the garden because they were so badly chewed and they came up perfectly with narry a bite to be seen. Again, we buy from Sarah Raven, Crocus or Amazon.
There are lots of other opinions on how to stop slugs in the garden; Sarah's grandma always uses coffee grounds and egg shells around delicate plants but her hostas are in shreds so we don't think much of that solution! The methods above work for us but every garden is different; we have such a huge amount of wildlife, including frogs and hedgehogs, in the garden that it may well be these guys who are keeping the slug population under control.
I do feel almost bad about my war on slugs, they are actually really fascinating creatures and we are trying to adopt a more live-and-let-live approach and move towards entirely barrier-based methods of slug control.
The RHS trial which has been running since 2014 is due to report in 2019 about the effectiveness of different types of slug control: https://www.rhs.org.uk/science/plant-health-in-gardens/entomology/rhs-projects-on-plant-pests/integrated-gastropod-management