Types of snails in the garden: useful and harmful

Few of the species of snails found in gardens prey on lettuce and other green plants. Many snails are even useful and should be encouraged in gardens.

A snail is not the same as a snail. Even if we are often disgusted by the greasy little animals, many land snail species are useful and important to our ecosystem. Nevertheless, some types of snails develop into a veritable plague of snails in the garden, especially in wet years. This article looks at some types of snails that are common in our country and shows which snails are more useful to us.

Types of snails in the garden: how many are there?

Snails, whose scientific name is Gastropoda, form a separate class within the mollusks (Mollusca). It is not possible to say exactly how many snail species there are in total, but their number is enormous. It is estimated that there are at least 85,000 species. We are particularly interested in the snails that can be found in gardens. These are among the terrestrial pulmonary snails (Stylommatophora), of which around 25,000 species exist worldwide.

How many snail species are native to Germany?

There are around 400 terrestrial snail species in Germany, but not all of them are native. Some of them were introduced and are referred to as neobiota or neozoa. These include, for example, the Spanish slug (Arion vulgaris) or the spotted Roman snail (Cornu aspersum). Around 50 terrestrial pulmonary snail species belong to the neozoa in Germany, the rest are considered native.

Useful species of snails in the garden

What are snails useful for? Not all snail species prefer fresh, green plant material. Some species feed primarily on dead plants and carrion and are therefore important decomposers in the material cycle. Sometimes useful snails in the garden even eat other snails or their clutches, so that they actively contribute to reducing the number of unwanted snail species. The useful species of snails found in our gardens mainly come from two families: the snails (Helicidae) and the slugs (Limacidae).

Snail snails (Helicidae)

Almost all shelled snails that can be found in our gardens come from this family. It is very species-rich and widespread in Europe. The various species of these snails feed mainly on dead plant material, which is why they usually do not cause any major damage.

Roman snail (Helix pomatia)

Roman snails are one of the snail species native to us. However, the number of Roman snails in the garden has decreased significantly in recent years, which is one continuous destruction of Roman snail habitats and effective chemical control is owed. That is why the Roman snail is now under nature protection in Germany. The shell of Roman snails reaches a size of 3 to 5 cm and is mostly clockwise. Since Roman snails usually survive the winter by turning into a freeze, Roman snails can reach an age of up to eight years in nature. The habitat of Roman snails should have a calcareous, rather moist soil and ideally be shady and warm. They are often found in sparse forests or bushes. Roman snails have many natural enemies. For example, ants, mites, birds of prey and small mammals primarily target young Roman snails with a still soft shell. Because of this, only about 5 out of 100 snails live to be more than two years old.

Tip: Have you ever found a snail on your salad and wondered if snails are really useful? If Roman snails do not find enough dead plant material, which is the case, for example, in very clean and As can be the case in clean gardens, they sometimes have no choice but to feast on fresh plant parts pass away So feel free to leave a few dirty corners so that the Roman snail doesn't have to compete with you for food.

Garden snail (Cepaea hortensis)

With a shell diameter of about 2.5 cm, garden snails are significantly smaller than Roman snails. The case is characterized by its light coloring with dark bands. The mouth of the shell is usually white, which serves as a distinguishing feature to the otherwise very similar grove snails. Garden snails can adapt to a wide range of habitats, but they are often seen in forests, bushes, hedges or tall herb beds. They are often found a little higher up on trees or hedges. Since they mainly feed on algae and not herbaceous parts of plants, they usually do not cause any damage in our gardens.

Slugs (Limacidae)

All snails without a shell are often lumped together and generally portrayed as harmful and unwanted. However, there are slug species that are useful, such as most slug species. A total of around 200 species of slugs are currently known. They feed mainly on dead plant material, algae, fungi and sometimes the clutches of other snails. The genera are horticulturally relevant Lehmannia, Limacus, Limax, Malacolimax. the tiger slug (Limax maximus) is also not afraid to attack and devour the rampant Spanish slugs, making it one of the few natural enemies of Spanish slugs. The Black Slug (Limax cinereoniger) is often found on composts, where it eats plant debris and fungi. The greenhouse slug (Lehmannia valentiana) is the only known slug species that causes damage - but only in the greenhouse.

What types of snails are a threat to garden plants?

In case of increased occurrence, the slugs (Deroceras reticulatum) and the Spanish slug (Arion vulgaris) pose a hazard to garden plants.

One thing to keep in mind is that not all plants are equally affected. Many are uninteresting to slugs or can even help scare slugs away from the bed. We have created an article for you that deals with slug resistant plants deals with and another one that shows you which ones Plants drive away snails.

In the event of an invasion, the grip of slug pellets may be indispensable. Our Plantura organic slug pellets reliably fights snails even in the rain and allows them to retreat to their hiding places without the formation of slime. It is gentle on beneficial insects and pets and even approved for organic farming.

Slugs (Arionidae)

What the various species within the slug family have in common is that the snail shell is largely there has receded and only the so-called mantle, which covers the front part of the body in adult slugs, remains has stayed. Slugs have their breathing hole on the right side, in front of the middle of the mantle. Another characteristic that distinguishes them from many other species of snails is that slugs can curl up. In the garden is primary the genus Arion relevant.

Spanish slug (Arion vulgaris)

Spanish slugs, commonly referred to as nasturtiums, have long been used as a prime example of a harmful, invasive species. It was believed that this nudibranch species was introduced from Spain in the 1960s and has since spread massively, supplanting our native snail species. However, more recent studies show that the Spanish slug does not occur in Spain and its actual origin cannot be clearly proven. It is undeniable that it has become widespread over the last few decades, so that it is now probably the most common snail species in Germany.

Adult animals are relatively large snails with a length of 7 to 14 cm. It is difficult to identify them precisely, as they vary greatly in color - from brown to orange to grey-green - and are therefore very similar to other slugs. They are therefore often associated with the red (Arion rufus), browns (Arion fuscus) or blacks (Arion ater) slug confused. These species often only cause comparatively little damage or no damage at all in the bed, but are nevertheless - and usually unnecessarily - fought with all their might. The red slug is even considered endangered and should not be eliminated if possible.

To avoid confusion, the nasturtium should be identified exactly. The determination of the young animals works better than with adult animals, which are usually much lighter, almost bright orange-yellow and have two coffee-brown longitudinal stripes. Spanish slugs are omnivores but prefer fresh plant material and are particularly fond of it marigolds (tagetes), valerian (Valerianaofficinalis) and pumpkin plants (Cucurbita) apart. Spanish slugs are also cannibals and will eat the clutches of other slug species, giving them a competitive advantage.

Garden slug (Arion hortensis) and common slug (Arion distinctus)

These two snail species are very closely related and difficult to tell apart, which is why they were often simply referred to as garden slugs in the past. The adult animals are a maximum of 5 cm long, but often remain smaller. The back of the animals is mostly blackish to dark blue with a tinge of brownish. Separated by a lighter, yellowish stripe, there is a darker longitudinal stripe on both sides, the so-called bandage. The sole is usually yellowish in color and the body mucus is also yellowish in color. The two garden snail species feed on herbaceous, chlorophyll-rich – i.e. green, fresh – plant material. They often live in the ground, where they eat parts of plants under the topsoil. The garden snails can hibernate in all stages - from the egg to the adult animal - which is why you can find all stages in your garden at any time of the year. As a rule, garden slugs and common slugs live for about nine months.

Field slugs (Agriolimacidae)

The mantle of field slugs usually covers at least a third of the body. The relatively small breathing hole is in the back half of the mantle. Its tail end is keeled, ie tapering to a point, like the keel of a ship. Although this is the largest family of slugs, one species in particular is perceived as harmful in our gardens - the slugs.

Reticulated field slug (Deroceras reticulatum)

The netted field snail is 3.5 to 6 cm long and is the most common native snail species in our country. Their color varies from creamy-white to slate gray to reddish brown. Characteristic are the darker spot markings, which sometimes result in a real net, and the clearly furrowed skin. Field slugs are particularly dependent on moisture and are sensitive to light, which is why they are nocturnal. Reticulated field slugs are omnivores, but prefer fresh plant material. This species of slugs can also attack seeds and young seedlings, which often leads to the culture failing to emerge. Field slugs lay their eggs until autumn. In the spring, the young snails hatch and create two to three generations per year under optimal conditions.

Tip: The reason why the field slug has such a high potential for damage is that, in contrast to other snails, it is able to develop several generations per year.

Even the adult snails survive in mild winters and become active on particularly warm days. These surviving snails can do a lot of damage early in the year.

If you know what types of snails occur in your garden, you can take control measures if necessary. The fact that you don't have to reach for the chemical club immediately and what else you can do is discussed in our article fight snails explained in more detail.