Giant Hogweed (Heracleum mantegazzianum) is a plant that typically grows to heights of 2.5 m and has been known to reach height of 7 m. The sap of giant hogweed causes phytophotodermatitis in humans, resulting in blisters, long-lasting scars, and—if it comes in contact with eyes—blindness. These serious reactions are due to the furocoumarin derivatives in the leaves, roots, stems, flowers, and seeds of the plant.

Himalayan Balsam (Impatiens glandulifera) is an introduced plant which has escaped from gardens and is rapidly colonising river banks and other areas of damp ground. It is an annual plant which grows to about 2 m with purplish-pink slipper shaped flowers in June - August. When the seed pods are mature, they explode when touched, scattering the seed. It is likely that the seeds are further spread by water movements. Himalayan Balsam forms dense stands which suppress the growth of grasses and native British plants leaving the banks bare of vegetation in autumn and winter and liable to erosion. Because Himalayan Balsam regrows annually from seed, any form of control carried out after the seed pods have formed will have no long term benefit

Ragwort (Jacobaea vulgaris) is a very common wild flower in the family Asteraceae that is native to northern Eurasia, usually in dry, open places, and has also been widely distributed as a weed elsewhere.

Ragwort is of concern to people who keep horses and cattle. In areas of the world where ragwort is a native plant, such as Britain and continental Europe, documented cases of proven poisoning are rare. Horses do not normally eat fresh ragwort due to its bitter taste. It loses this taste when dried and can become a danger in hay. The result, if sufficient quantity is consumed, can be irreversible cirrhosis of the liver.

Buddleia (Buddleja davidii) which originated in China, is viewed by the Department for the Environment, Food and Rural Affairs (Defra) as an invasive non-native species. Its "invasion history" has been charted from its introduction to the UK in the 1800s to the first record of the plant in the wild in 1922.

 It is commonly found throughout the United Kingdom and is often seen along railway tracks, urban wastelands and roadsides

The plant can cause damage to buildings, such as crumbling brickwork - its tiny wind-blown seeds can germinate in decaying mortar.

And the problems caused by buddleia to the management of the rail network are described by the Non-Native Species Secretariat as "significant"