On naturally wet sites and around large ponds and lakes, carr-like woodland can be established. Trees and large shrubs have a high transpiration rate and are able to drain soggy soil. They are, therefore, useful in wet depressions. However, along the edge of sealed water-bodies the loss of water is generally too great when tall woody plants are used. Designed carrs can develop a clear stratification into a tree layer, shrub layer and herb layer. The herbs can be sown, if the soil is largely free from weeds. Tall perennials can be established—this can be among short-lived ruderal weedy herbs. Competitive weeds, such as Urtica dioica or Phalaris arundinacea, should be removed before planting the desired perennials. Another possibility is to plant only trees and shrubs between existing spontaneous vegetation. If vines (for instance, Humulus lupulus or the North American Vitis riparia) are wanted to climb among the trees and tall shrubs, they should not be planted before the woody plants have reached a sufficient height.
In carr vegetation, woody plants will be responsible for the long-term effect. Perennials and short-lived species include shade-tolerant species and plants that are tolerant of open sites to guarantee a satisfying visual effect even before trees and shrubs shade the herb layer sufficiently.
Examples of woody plants include the following.
1 Alder carr: soggy soil, moderately flooded in spring, eutrophic, pH lightly acid to lightly alkaline, species native in Central Europe—proposed quantities for 100 m2:
• 15 Alnus glutinosa
• 5 Prunus padus
• 5 Cornus sanguinea
• 5 Euonymus europaeus
• 30 Ribes nigrum
• 5 Salix cinerea
• 5 Viburnum opulus.
2 Birch pine carr: wet soil, not flooded or only moderately flooded for a short time in
spring, oligo-mesotrophic, pH acid to lightly acid (<6), species native in Central Europe—proposed quantities for 100 m2:
• 10 Betula pubescens
• 3 Pinus sylvestris
• 10 Frangula alnus
• 50 Vaccinium uliginosum
• 5 Salix aurita
• 20 Ledum palustre
– dwarf shrubs:
• 300 Calluna vulgaris (sowing is possible on weed-free sites).
3 Mixed decorative carr: soggy soil, moderately flooded in spring, meso-eutrophic, pH
lightly acid to neutral, species native mostly to North America, added with other origins to produce a colourful effect—proposed quantities for 100 m2:
• 3 Taxodium distichum
• 2 Liquidambar styraciflua
• 5 Sorbus decora
•10 Cephalanthus occidentalis
• 10 Clethra alnifolia—along the edges
• 5 Ilex verticillata
• 5 Physocarpus opulifolius or Magnolia virginica on acid soil in mild climate
• 15 Myrica pensylvanica or Rhododendron viscosum on acid soil
• 15 Spiraea tomentosa
• 5 Viburnum trilobum.
Along the woodland edge, Rubus idaeus (Raspberry) can be established in groups. If not too wet, this can also be a cultivar producing fruits in autumn on shoots of the same year, such as ‘Autumn Bliss’. This enables simple maintenance: the edge can be mown late each winter or spring and there will be a visually attractive development of flowers and fruit in the same year.
Trees and shrubs can either be planted together with perennials or integrated into an existing wet meadow with site conditions suitable to each other. These herbaceous communities should be maintained as meadows until the canopies of the woody plants develop a shade that leads to a decline in the growth of the perennials. Shade-tolerating perennials can be introduced, when this occurs.
When trees and shrubs are planted together at the same time with shade-tolerating perennials, these should be combined with several tall wet-meadow forbs (dominant species) as interim shade creators. With increasing shading these tall perennials will be weakened and will gradually become substituted by the more shade-tolerant perennials (Table 8.1).