Lepidium didymum Lesser Swine-cress DD I
This introduction from South America has spread very well in the South and Central parts of England but according to Stace is less frequent in the North. In this part of the North of England however it has taken a very good hold and has appeared regularly in flower beds and on waste ground in our area for over 20 years. The flowers are tiny (less than 0.5 mm often) and if the petals are present they are often smaller than the sepals. The fruit is said to be reticulate (covered in a net-like pattern) but in comparison with L. coronopus (Swine-cress) it is smooth. Under a hand lens the stems are sometimes hairy. Recognition from adult height isn't through seeing any of these features though, what you first notice is a sprawling very light green plant which needs investigating.
Common in Wales, England and southern Ireland L. didymum does not appear to have successfully invaded Scotland yet.
Northwich new shrub beds, 17th June 2005
Added on October 18th 2005, updated 6th December 2008, updated 20th March 2010, updated Se3 4th May 2010