Invasive species

Article Gallery: 

There are some trees, shrubs or plants that once planted (they are not usually part of the natural habitat) take over the soil and light resources preventing other (desired) species from developing.

For Europe
Ailanthus altissima (Tree of heaven)
Amorpha fruticosa (Desert false indigo)
Carpobrotus edulis (Hottentot fig)
Caulerpa racemosa (Grape caulerpa)
Caulerpa taxifolia (Mediterranean clone)
Crassula helmsii (Australian swamp stonecrop)
Elodea canadensis (Canadian pondweed)
Fallopia japonica (Japanese knotweed)
Gleditsia triacanthos (Honey locust)
Heracleum mantegazzianum (Giant hogweed)
Hydrocotyle ranunculoides (Floating pennywort)
Impatiens glandulifera (Himalayan balsam)
Myriophyllum aquaticum (Parrot feather)
Rhododendron ponticum
Robinia pseudoacacia (Black locust)
 
For North America  
Acroptilon repens (Russian knapweed)
Ailanthus altissima (Tree of heaven)
Albizia julibrissin (Silk tree)
Alliaria petiolata (Garlic mustard)
Ardisia crenata (Coral ardisia)
Arundo donax (Giant reed)
Berberis thunbergii (Japanese barberry)
Bromus tectorum (Downy brome, cheatgrass)
Butomus umbellatus (Flowering rush)
Carduus nutans (Musk thistle)
Casuarina equisetifolia (Australian pine)
Caulerpa taxifolia (Caulerpa, Mediterranean clone)
Centaurea diffusa (Diffuse knapweed)
Centaurea maculosa (Spotted knapweed)
Centaurea solstitialis (Yellow star thistle)
Cinnamomum camphora (Camphor laurel)
Colocasia esculenta (Wild taro)
Conium maculatum (Poison hemlock)
Cortaderia selloana (Pampas grass)
Cosmos sulphureus
Cynanchum louisae
Cynanchum rossicum (Dog-strangling vine)
Cytisus scoparius (Common broom, Scotch broom)
Dioscorea bulbifera (Air potato)
Egeria densa (Brazilian waterweed)
Eichhornia crassipes (Water hyacinth)
Elaeagnus angustifolia (Russian olive)
Elaeagnus umbellata (Autumn olive)
Euphorbia esula (Leafy spurge)
Fallopia japonica (Japanese knotweed)
Hedera helix (English ivy)
Heracleum mantegazzianum (Giant hogweed)
Hieracium aurantiacum (Orange hawkweed)
Hydrilla verticillata (Hydrilla)
Imperata cylindrica (Cogon grass)
Ligustrum sinense (Chinese privet)
Ligustrum vulgare (Eurasian privet)
Lonicera japonica (Japanese honeysuckle)
Lonicera maackii (Amur honeysuckle, bush honeysuckle)
Lonicera morrowii (Morrow's honeysuckle, bush honeysuckle)
Lonicera tatarica (Tartarian honeysuckle, bush honeysuckle)
Lygodium japonicum (Japanese climbing fern)
Lygodium microphyllum (Old World climbing fern)
Lysimachia nummularia (moneywort)
Lythrum salicaria (Purple loosestrife)
Melaleuca quinquenervia (Melaleuca)
Melia azedarach) (Chinaberry)
Microstegium vimineum (Asian stilt grass)
Mimosa pudica (Mimosa)
Myriophyllum spicatum) (Eurasian watermilfoil)
Onopordum acanthium (Cotton thistle)
Paederia foetida (Skunk vine)
Panicum repens (Torpedo grass)
Pastinaca sativa (Wild parsnip)
Persicaria perfoliata  (Chinese tearthumb)
Phragmites australis (Common reed)1
Potamogeton crispus (Curly-leaf pondweed)
Pueraria montana var. lobata (Kudzu)
Rhynchelytrum repens (Natal grass)
Rosa multiflora (Multiflora rose)
Rubus armeniacus (Blackberry)
Rubus phoenicolasius (wineberry)
Rumex crispus (curled dock or curly dock)
Salvinia molesta (Giant salvinia)
Sapium sebiferum (Chinese tallow)
Schinus terebinthifolius (Brazilian pepper tree)
Solanum viarum (Tropical soda apple)
Spartina alterniflora (Smooth cordgrass)
Striga asiatica (Witchweed)
Tamarix spp. (Saltcedar)
Trapa natans (Water caltrop, water chestnut)