Five ‘notorious green alien’ invasive plants you can find within France

Not all wildflowers that you see in the countryside are native to France. At least 40 species, including some spectacularly conspicuous ones, are classed as undesirable invaders. Brought from elsewhere, often as garden plants, they have escaped from cultivation and gone native, displacing indigenous species and causing havoc to local ecosystems. Where they cause serious trouble, efforts are made to eradicate or at least control them. Some, including pampas grass (Herbe de la Pampa – Cortaderia selloana), giant hogweed (Berce du Caucase – Heracleum mantegazzianum) and Himalayan balsam (Balsamine de l’Himalaya – Impatiens glandulifera), are well known to botanists, conservationists and nature lovers. Here are five more notorious green aliens.

1. Annual ragweed (Ambroisie à feuilles d’armoise – Ambrosia artemisiifolia)
Native to the Americas, this annual herbaceous plant now has a strong, undesirable presence in the Rhône Valley and the Lyon basin, and it is gaining ground elsewhere. It competes with crops and impoverishes the soil, and some people are allergic to its pollen.

2. Butterfly bush (Buddleia de David – Buddleja davidii)
These bushes, often planted in gardens, produce beautiful blooms that, as their English name suggests, attract some species of butterfly, but certainly do not feed all native insects. Buddleias are prolific colonisers of neglected urban spaces, where they prevent other plants from growing. The seeds are carried by wind or vehicle wheels, allowing them to take root wherever they land.

3. Japanese knotweed (Renouée du Japon – Reynoutria japonica, aka Fallopia japonica)
Native to East Asia, specifically Japan, China and Korea, this species of perennial herbaceous plant is particularly prevalent in eastern and central France but is spreading everywhere. With its long stems and resistant roots, it colonises riverbanks and the sides of ditches, smothering other plants and weakening soils. Even a small fragment of rhizome is enough to restart a new colony. It is truly a tough pest to eradicate.

4. Water primrose (Jussie – Ludwigia grandiflora)
This aquatic plant, native to South America, was introduced to France in the 19th Century as an ornamental pond plant. Little by little, it has since invaded lakes in the Landes, the Brenne, the Marais Poitevin and elsewhere. Its floating mats cover the surface of waterways and prevent light from reaching other aquatic plants.

5. Pokeweed (Raisin d’Amérique – Phytolacca americana)
This American import has been popping up in gardens, fields and other unwanted places since the 1990s. It disappears in winter but grows rapidly in spring to become highly conspicuous. Eventually, it produces spikes of red berries which are toxic to humans and animals and should therefore be avoided, especially by children who may be attracted to them. The song Polk Salad Annie, popularised by Elvis Presley, is about this dodgy customer.