Slug-less, almost

Hosta 'Wide Brim' — just one bite!What’s going on here? I’ve just realized that I haven’t seen a slug all summer. This is so strange. Usually my early morning garden prowls reveal slimy trails leading to the brazen offenders at their breakfast, but not this year. I’ve provided the pricey variegated hybrid hostas favoured by these loveless creatures, though they’ve attracted little attention.

Other years, my clumps of green and white ‘Patriot’ and ‘Brim Cup’ have been shot through with holes, and in some cases, the tender white sections were completely skeletonized. It’s a fact: some slugs can eat faster than plants can grow. Damage this year is minimal—some leaves are entirely unmarked, while others have just a few tiny holes. Hostas with generous white or cream leaf tissue are beefsteak to a slug, but not this summer.

Certainly the extended wet spring set up ideal conditions for slug (a.k.a. gastropod mollusks without a shell) habitats. Was it in May that we seemingly had non-stop rain? (Now I understand the wisdom of those gardeners who keep daily weather diaries). Well it rained a lot, and slugs should have been proliferating. I haven’t taken a census of the slug population per square metre of garden bed, but evidence suggests there are significantly fewer than in past years.

Prolonged midsummer heat and drought cause slugs to become inactive and retreat to whatever moist circumstances they can find. I hope they will be disconsolate in their burrow and give up the fight. Nevertheless, having a canister of powdered sulphur close to hand is smart anti-slug policy. When sprinkled generously on the soil surface around vulnerable target plants, it wards off slug attentions. Of course the sulphur must be renewed frequently, but unlike the commercial slug bait products (containing metaldehyde or iron phosphate), it does no damage to soil, animals or humans.  Sulphur benefits alkaline soils, helping to lower pH, although it’s slow acting and won’t permanently acidify soil.

There are other changes in insect visibility. I’ve had summers when earwigs were so numerous that they literally dripped off the plants, but there have been few earwig sightings this summer. Entomologist Eric Grissell, author of Insects and Gardens (Timber Press, 2001), informs me earwigs are victims of bad press generated by overly fastidious gardeners who rake their soil clean.

Earwigs are light-sensitive nocturnal predators that feed on mites, nematodes, insects, and decaying organic matter. Roses and clematis aren’t at all to their taste, but they’re forced to eat these flowers when their preferred food is eliminated by tidy gardeners. Where leaf litter forms a mulch over bare soil, earwigs will use it as a complete habitat, feeding on small insects, plant detritus and decaying matter, while at the same time hiding from daylight and tending their babies (a mother earwig will defend her eggs). 

This is timely information just before the big autumn leaf drop.  Was there ever a better reason for mulching all exposed soil with a three-inch layer of fallen leaves? So, do it!