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Complementary informations

 

This section delivers complementary information related to measures

included in the code of conduct on invasive plants.

  

Names and synonyms of invasive plants

Invasive plants have several names and/or synonyms. It is very important to be sure about the identity of the plants you grow, sell or plant in order to know if they are not part of the list of invasive plants in Belgium. To guarantee this, plants used should be correctly and fully identified with the name of the genus and species as well as the common name.
For cultivars, varieties or hybrids, the name of the type should also be mentioned in addition to genus and species, with the required standard commonly used (e.g. for a cultivar: Buddleja davidii ‘Harlequin’; for a variety: Berberis thunbergii var. atropurpurea; for an hybrid: Aster x salignus). Lots of plants are sold with only the name of the genus and the cultivar, without indicating the name of the species (e.g. Lupinus ‘Gallery blue’). It is therefore impossible to identify which species is used.

 
The list of names and synonyms of invasive plants

 

Garden waste management

Deposit of garden waste or plant waste (for terrestrial or aquatic plants) containing fragments of invasive plants is a well-known vector contributing to the spread of those species. Seeds, small fragments of stems, roots or rhizomes can easily regenerate populations in nature. Garden waste or plant waste (including compost) must never be dumped in the countryside. Aquatic plant waste must never be evacuated in rivers. Deposit of garden waste in the wild is an illegal act in Belgium. Plant waste should be managed following prescriptions recommended by legislation (evacuation to authorized collecting sites, composting, etc.).

 

garden_waste2_web  garden_waste_web

Deposit of garden waste in the wild. On the left garden waste contains fragments of Prunus laurocerasus (photos: M. Halford) 

 

Recommendations about plantation

Species included in annex II of the code should be used with care. They may become invasive in some natural habitats or in specific conditions, including in parks and gardens. Planted in urban, periurban or rural areas, they may escape and invade habitats of high ecological value. It is recommended to avoid planting these species near those habitats. Alternative plants can be proposed instead of these species.

Habitats of high ecological value and invasive species in annex II

 

Recommendations about alternative plants

Partners are recommended to promote alternative plants instead of invasive plants mentioned in the code. Each partner is free to identify which alternative plants he will promote. An alternative plant is a non invasive species which can be used as a substitute to invasive plants, meaning a plant with similar ornamental/functional properties but presenting no risk for biodiversity. Horticultural catalogues are full of plants meeting these criteria. A brochure and a folder with a selection of alternative plants are now available in the Alternative plants section of this website !

Cautions should be kept with exotic plants because it is presently impossible to predict which species could become invasive in the future (especially in the perspective of climate change). Some exotic plants currently considered as non-invasive could become invasive in 10 years, 50 years, 100 years or later. This is due to the lag phase observed between the initial introduction and the expansion phase (see FAQ, question 11).

The Belgian list system of invasive alien species should not to be considered as fully exhaustive. Some exotic species not yet assessed by the Belgian Forum on Invasive Species may have some invasive behaviour and could be at risk for biodiversity.  For example other Cotoneaster species (e.g. Cotoneaster damneri, C. simonsii, C. microphyllus) are considered as invasive in Great Britain and France. A list of species that should be assessed in the future will be available very soon on the website of the Belgian Forum (http://ias.biodiversity.be). It will include organisms that may be at risk for biodiversity either because they recently expanded their geographic range or because environmental damage has been recently reported in in Belgium or in neighbouring areas. Although their final risk assessment score is not yet established, those species should not be proposed as alternative plants based on the precautionary principle.

Do not forget that species included in the alert list by the Belgian Biodiversity Platform (Akebia quinata, Carpobrotus edulis, Carpobrotus acinaciformis, Echinocystis lobata, Lonicera japonica, Phytolacca americana, Cabomba caroliniana) are also invasive plants and must therefore not be proposed as alternative. 

 
 
Information about cultivars

Numerous cultivars are derived from invasive plant species, with varied characteristics selected through breeding programs. It is not proven if all those cultivars have the same invasive potential than the species. Some cultivars may have a similar or a higher invasive potential, whereas others may be less invasive and therefore present a lower risk. Traits such as resistance to diseases or pathogens, rusticity (resistance to cold), high amount of flowers, easy multiplication, high germination rates or high growth rates may confer or even enhance the invasive potential. On the other hand, dwarf cultivars, late-blowing cultivars, sterile cultivars (stable in time) or cultivars with a low fertility are supposed to have a lower invasive potential. There are presently few scientific data available about this issue in Belgium. Information should be progressively collected in order to identify the types (cultivars, varieties, hybrids) presenting a higher or a lower risk of becoming invasive.

Risks also exist for invasive plants used as rootstocks for grafting. A scientific publication recently analysed the issue with Pyrus calleryana (considered as invasive in the United-States), demonstrating that rootstocks can significantly facilitate spread into semi-natural habitats (read this article). In Belgium, several species are commonly used as rootstocks (for example Acer negundo, Acer rufinerve, Amelanchier lamarckii, Fraxinus pennsylanica, Prunus laurocerasus, Robinia pseudoacacia, Rhododendron ponticum, Rosa rugosa and Quercus rubra).

 

Specific labelling

For nursery professionals (producers, sellers, wholesalers, etc.), specific labelling is another good practice for disseminating adapted information about the potential risks of invasive plants (for species included in the annex II of the code).

 

Examples of specific labelling

Cotoneaster horizontalis (Rosaceae)
Wall cotoneaster
Native from China
Small shrub used as ground cover
Invasive in protected habitats like chalk grasslands, dry grasslands, where it modifies botanical composition and vegetation dynamic. Also present in rocky slopes and abandoned quarries.
Do not plant near chalk grasslands or rocky habitats. It can easily escape and invade semi-natural habitats.

 

Rosa rugosa (Rosaceae)
Rugose rose
Native from Eastern Asia
Shrub used as ground cover, wind break and landscape planting. Tolerant to salt and drough.
Highly invasive in protected habitats like costal dunes or sand grasslands, where it threatens native flora, fauna and modifies ecosystems properties.
Do not plant near coastal dunes. It can easily escape and invade semi-natural habitats. 

 

Spiraea alba (Rosaceae)
White meadowsweet
Native from North-America
Ornamental shrub invasive along rivers or in wetlands, where it can form dense populations outcompeting native flora and fauna.
Do not plant along rivers or near wetlands.

 

If you wish to apply specific labelling to other species included in annex II, please do not hesitate to contact us. The AlterIAS team will give you specific information related to those species.