The aliens have landed....

Here in Langthorpe on the river Ure, you cannot avoid seeing a couple of invasive alien plants on the banks of the canal cut.  The first is a single Giant Hogweed Heracleum mantegazzianum, which at just under 2 metres in height has just passed its prime with many of the white flowers now turning to seed.

Giant Hogweed

This impressive plant which can grow to 3 metres in height is originally from south-west Asia, and was introduced as a monumental curiosity by 1820, and was first  recorded in the wild in Cambridgeshire in 1828, and has since spread to much of the UK, the seeds spread along watercourses.  It is, however, a dangerous plant, in that its sap contains toxins that once on the skin reacts with sunlight to cause severe burns and blistering which can last several months, and if it makes contact with eyes can cause blindness.  Once the sores have subsided, the effects of the rash can last for five years or more.

The other plant that seems to be everywhere at the moment is the Himalayan Balsam Impatiens glandulifera with such interesting common names as Policeman's Helmet and Gnome's Hatstand, this too can grow to 2.5 metres, often seen in damp margins and roadside verges.  

Himalayan Balsam

Himalayan Balsam

This plant is also from Asia, introduced to Britain from Kashmir by Dr Royle at Kew Gardens in 1839, it too escaped and spread along water courses by 1855.  Now widespread across much of Britain, but rather patchy in the borders and Scotland, it can grow in such profusion that it can shade out many native species.  It is a pest species, and its management and removal is a major headache in many areas, and of course a cost to local authorities and nature reserves.

One lesser known use for the plant is that you can eat it!  The young leaves can be used as a vegetable but have to be cooked to negate the effects of calcium oxalate, and the dried seeds can be used to make curries.  

Some of these well-meaning plant-hunters bringing unusual and exotic flora and fauna back to Britain have a huge amount to answer for.