Gardening Advice

The main enemy, the common garden snail

The period

April: 25 000 salad vegetables planted in our kitchen garden at Villandry
The main enemy: the common garden snail

  • We are lucky enough to have few or no slugs, but the methods for protecting crops are the same for snails as for the three species of slug found in amateur gardens.
  • Red slug
  • Garden slug, measuring 3 to 4 cm
  • Grey slug, 3 to 5 cm

Slugs and snails have the same purpose: to devour seedlings, soft leaves, and sometimes fruits and roots. Their gluttony takes place mostly at night and in wet weather; at Villandry, the damage lessens considerably with the fine weather of May.
It is not a case of completely destroying snails and slugs, which can serve as food for other animals that are useful to the gardener, such as hedgehogs and ground beetles. The important thing is to protect your crops against the appetite of these gastropods without using substances that are harmful to the environment.

Mechanical methods

At Villandry, our kitchen garden consists of four linear miles of box hedging, which offers a wonderful refuge for families of snails.
On mornings after wet nights, the gardeners comb the entire kitchen garden, inspecting each avenue and box hedge in almost military fashion, and gather up the snails in a net before transferring them to the hedgerows along the banks of the River Cher.

Tiles or planks can also be placed in the garden to serve as shelter for slugs. They must be regularly turned over and the slugs collected.
Wood ash is a common means of protecting seedlings. A barrier must be made around the cultivated area, but it is vital to repeat the operation after each rainfall.
Beer traps are also well known: a container dug into the surface of the ground, holding a small quantity of beer, attracts the slugs, which then drown in it. But it has yet to be proven how effective a method this is, and it often captures other species which are useful to the garden.

Chemical and biological methods

Take all your old stocks of blue pellets (metaldehyde-based) to your local recycling centre in special containers for chemical waste; this substance is highly toxic for both pets and wild animals like hedgehogs.
It can easily be replaced by iron phosphate-based appetite-suppressing pellets. Blue like the metaldehyde pellets, these are biodegradable and do not present a risk to animals.
They are spread over damp ground, according to the dosage instructions, and are then ingested by the snails and slugs, which return to die in their hideaways. Early in the growing season, the pellets must be reapplied frequently. Any uneaten granules break down into phosphate and iron, which are elements naturally present in the soil.
Nematodes can also be used. These are microscopic worms (phasmarhabditis hermaphrodita) sold in the form of packets of powder to be diluted with water. A packet of 12 million nematodes is sufficient for 40 m² of garden, and will be effective for six weeks provided the ground is kept damp. The nematodes move around in the soil, penetrating the bodies of the slugs and releasing bacteria which kill them. Nematodes are sold under the brand name ‘Nemaslug’. A packet of 12 million costs €29.90 from www.magellan-bio.fr.

Laurent Portuguez
head gardener 

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