Primslips or Cowroses?

The wild flower conservation charity Plantlife is conducting a poll to find Britain's favourite wild flower and the primrose Primula vulgaris is a strong contender to take the title. Currently it is in top position in Scotland and Wales, second in England and third in Northern Ireland.

Primrose is primarily a plant of woodland edges, glades and hedgebanks, growing best in dappled shade and in moist soils. It's also a very variable plant, thanks to its breeding system, where there are two forms of flower - pin-eyed and thrum-eyed - with the stamens and stigma arranged in a way that ensures cross pollination when insects travel from plant to plant. 

Pin-eyed flowers have their stigma at the top of the floral tube and their stamens lower down, whereas ...

... thrum-eyed flowers have stamens at the top, with the stigma hidden underneath them.  It's an arrangement that maximises the chances of cross-pollination, reinfornced with an incompatibility system where the flower's own pollen will not normally germinate on its own stigma. The cross-pollination that this enforces generates genetic variability within the population - compare the broad-petalled flower above with ....

.. this one which has much narrower petals.

Primrose also readily crosses with .....

....... cowslip Primula veris wherever the two species meet, typically where woodlands meet the pastures that are the favoured habitats of cowslips. 

Populations of false oxlips, the natural hybrid between the two species, show almost every grade of intermediate form between pure cowslip and pure primrose..... with what you might call primslips and cowroses in between!

Cowslips typically have these small, intense yellow, downward-pointing flowers whereas .... 

..... false oxlip flowers tend to point outwards or even upwards and are larger and paler coloured. The false oxlip - with an injection of genes from a cross with at least one other more colourful European species ....

....... is the ancestor of the gaudy, very popular polyanthus that is the mainstay of so many municipal bedding schemes in spring.