The most abundant and fastest growing weed on my allotment plot is this plant, the Speedwell Veronica persica. Only first recorded growing wild in Britain in 1826, it’s an extremely widespread and successful plant.
‘It has a high potential seed production….The species also forms a persistent seed bank, and the seeds, which show little innate dormancy, are capable of germination during every month of the year….two generations may be produced in a single season.’ (Grime p606)
It is one of 3 speedwells that are found in arable land, the other two are V polita and V agrestis
Of the Figwort family(Scrophulariaceae), the Veronica genus is the only one to have 2 stamens and 4 corolla lobes. The above photo shows the 2 stamens of V persica.
One of the diagnostic features of V persica in comparison with V polita and V agrestis is the larger size of the corolla of V persica. At this time of year its difficult to find the flowers and they tend to be closed and inconspicuous. Another important feature is the shape of the seed capsules which with V persica are held at an angle away from each other as this photo shows. However if you look at the sketch in the first photo, the shape is not present when the seed capsule is not yet ripe.
Although not a diagnostic feature it is noticeable how the seeds are held on long pedicels (flower stalks)outside of the line of the leaves.