Palatability to slugs and snails

Relatively little is known about the palatability of seedlings of different species to slugs and snails. As a general rule, as seedlings age they become increasingly less palatable, due to increases in the concentrations of various chemical substances and, in some cases, morphological features, such as surface hairs (Table 6.13). Trollius europaeus, for example, is rarely grazed by slugs as an adult, but is highly palatable as young seedlings (Hitchmough 2003). The same also appears to be true for many Primula species. Some forbs are attractive to molluscs even as adults and are correspondingly ephemeral in landscape projects. In sites with high densities of slugs and snails, control of these

Table 6.14. Examples of particularly robust but non-invasive forb species

Dry meadow

Damp-wet

meadow

Prairie

Annuals

Buphthalmum

salicifolium

Centaurea nigra

Aster laevis

Agrostemma githago

Dianthus

carthusianorum

Euphorbia palustris

Eupatorium maculatum

Centaurea cyaneus

Galium verum

Geranium sylvaticum

Helianthus mollis

Chrysanthemum

segetum

Malva moschata

Geranium x magnificum

Rudbeckia fulgida var. deamii

Papaver rhoeas

Origanum vulgare

Persicaria bistorta

Rudbeckia subtomentosa

Papaver somniferum

Papaver orientale

Sanguisorba obtusa

Silphium integrifolium

Phacelia tanacetifolia

Primula veris

Sanguisorba

officinalis

Veronicastrum virginicum

Rudbeckia hirta

herbivores during the emergence period will normally greatly increase the diversity and density of sown and weed species (Figure 6.10).