Wednesday, May 30, 2012

The slimy menace


The garden still looks pretty good this spring, its mostly later-flowering species which are being damaged.


Until this spring I don't think I had understood just how damaging slugs and snails could be. I mean, like most gardeners, I have had to fight the little ******s off vegetable seedlings and the occasional emerging perennial, but never the wholesale onslaught the garden has suffered this spring. 
 
Prof. James Hitchmough, up at Sheffield, always went on about them, a bit obsessively, I thought. Now I see why. I remember Tony Kendle, an academic botanist who went on to work at the Eden Project in Cornwall, once telling me that he thought that localized extinctions of native species could be caused by molluscs. So, they really can have an ecological impact.

In my last garden, we had very little problem, and in this one, not much of a problem until last autumn when numbers began to build up. This spring the numbers of the things are incredible, and exacerbated by a long cold spring, in which the animals can operate, but many perennials are growly only slowly, so they can be continually grazed as they emerge. I am convinced now that they are capable of killing established perennial clumps in these conditions. 
 
They are highly selective, and in fact the number of vulnerable species is actually quite limited. I had already resigned myself to regarding some genera as almost ungrowable because of them – Helenium might be one, Asclepias certainly. Most of what I grow is actually unaffected. This year though they have really gone for Veronica austriaca, many asters, nepetas, aconitums, coreopsis, ligularia (well known snack) , baptisia, and most devastatingly, as it is an iconic plant in our garden, joe pye weeds – Eupatorium fistulosum/maculatum.

It is pretty obvious they can't eat anything with hairy leaves, but there must be chemical defences some plants have which means they don't get touched. Aquilegia and Thalictrum look very juicy and defenceless but seem ok. Aster are odd: A. laevis for e.g. is badly affected, but A. puniceus, novi-belgii, novi-angliae all look fine, Since some of these, like novi-belgii and a couple of odd American species I am trialling are very aggressive spreaders, they are going to have a clear ecological advantage here.

What to do? I'm very glad I did some research ages ago on good old-fashioned metaldehyde slug pellets, as they are far the simplest, cheapest and most effective way, and I can use them without feeling eco-guilt. Several years ago, at a time when I was also questioning the organic movement, I became suspicious that there was little evidence of them being harmful to wildlife, I had phoned round several conservation organisations, and none of them could come up with any real links to wildlife deaths, Government statistics on wildlife poisonings drew a blank too. Another eco-myth? James Hitchmough was pretty sanguine about using them too, having looked at the academic literature – he'd even done a research project which involved students catching and identifying them at night (the things you can make students do). Metaldehyde doesn't hang around in the soil either. So a few pellets (you don't actually need very many) in the crowns of vulnerable plants, leads to a satisfying array of dying slugs the next day. Best in dry weather so they dry out quickly and die 100%. Late evening slug hunts and lots of vindictive stamping are effective too. 
 
Longer term, I think we may have to get the chickens in. Once vulnerable seedlings are up and running, I'm hoping Jo will let the chickens have free rein of the garden, and they can go round and gobble up the next generation before they breed. But next spring I shall be ready and waiting.

8 comments:

Søren said...

Oddly enough this seems to be a poor year for slugs here in Denmark; we're not seeing anything like the normal numbers, and the damage to the garden is correspondingly smaller than the same time last year.

I do feel for you, and I too use a combination of pellets, boots and collecting them in buckets and pouring boiling water over them...

balsamfir said...

Now I know what happened to all the Heleniums I've planted over the years. I used the diatomaceous earth for hostas, and it did make a difference. Maybe I'll try again with awareness.

Telegraph Tea Room Garden School said...

I am not sure Noel whether the biological control, involving a nematode is good on large areas, and whether or not there is actually a nematode that destroys slugs in the soil? I know we used some biological control at Lost Gardens of Heligan, but that may have been only in the productive gardens, and for something else, and not the flower gardens. I will have to look back in my notes.
Slug pellets are brilliant though for instant results! Anyway, out here in Canada, I am seeing more evidence of slugs in Ontario than Nova Scotia. I will be watching carefully though, at the moment just about coping with all the other critters coming on my soil kicking up dirt and my newly sown seed! Anyway your gardens look fabulous, hopefully most will recover and put out new growth, and flower a little later.

Petra/Oxonian Gardener said...

Funny how their tastes change. Last year my Eupatoriums suffered and in particular my Vernonia too. This year its the Agastache's. Completely depleted, but thankfully doing their best to come back. Vernonia again seems a tasty treat. Thankfully the so described tastiest treat for slugs my Tricyrtis have never really suffered, though I may regret saying that. Will be watering with nematodes which works well for me. Don't like seeing blue slug pellets......! ps. Enjoyed this post immensely. Very amusing.

Capital Gardens said...

I'm not saying we shouldn't be peppering our gardens with slug killer, because they definitely ruin gardens, but isn't nature supposed to be in some sort of 'perfect balance'? I wouldn't have thought it could get to a point where there are enough slugs/snails to kill on an entire plant species or two, unless it's caused by us interfering with them? Still, maybe we should all follow the French and start eating them for dinner, more humane than just killing them for no reason right? :)

Maggie said...

I had a big slug problem for the first time ever when we moved into our new home five years ago. A summer dedicated to going out at night with a headlamp on and dropping them into a bowl filled with vinegar did the job quite well. We've been virtually slug free until this year. Guess I'll have to go on the attack again.

queerbychoice said...

In my experience, Helenium is perfectly growable with a high population of snails. There just isn't much purpose in growing it because you can't actually see the plants at all through the thick blanket of snails covering every part of the plant. Not my idea of pretty!

BasiaK said...

In my garden they used to go for campanulas and especially Aster novi-belgii. These proved to be vewy tough though and survived, but the leaves are so badly damaged that next season it will be metaldehyde from early on. I prefer looking at dead slugs (those huge orangey ones!) rather than at completely holed leaves.