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.

Genes on the Run

There were some fabulous patches of primroses in flower along the Northumbrian coast near Howick last weekend and amongst them were a few plants like the one below, with pink petals.

Plants like this are almost certainly the product of crosses between our native primroses and exotic cultivated species ..... perhaps between plants growing in the gardens at Howick Hall and their wild cousins on the grassy bank just above the strand line at Howick Haven, cross pollinated by a bee. Some people get very steamed-up about potential threats to our wild flora posed by occasional crosses with GM crops (not that we grow any of these in Britain yet) but there's no doubt that some cultivated, exotic plant species in gardens have been exchanging genes with some of  closely-related native wild flowers for a long time. The garden polyanthus is the product of hybridisation between primroses, cowslips and an unknown continental Primula species that contributed blue and red pigments to the mix, and when polyanthus is grown in the proximity of primroses and cowslips it exchanges genes with them. Exotic columbine (Aquilegia) species have a propensity to hybridise with our native wild columbines - now rare - so any Aquilegia vulgaris growing within bee-flight distance of a garden with cultivated Aquilegia species is potentially at risk of 'contamination'. Does it matter? I think not. I've been admiring the primroses between Cullernose point and Howick for thirty years now and there are no more pink-flowered primroses there now than when I first walked that path. They just add to the interest of this glorious coastal footpath.