Ahh, the primroses! Don’t they look wonderful - those chalky shades of yellow, brightening up our hedgerows in early spring. But how much do you know about primroses (Primula vulgaris)? How much do you want to know about primroses? Have you ever pondered on the sex life of primroses? Well I have. ... Did I really just say that... how weird am I?
Anyway... some plants are self-fertile and are very successful - dandelions, for instance. But self-
fertilisation limits genetic variation and this in turn inhibits their ability to evolve and adapt. Many plants have adopted cross-fertilisation and this is achieved in different ways.
Hazel is monoescious. Male and female flowers on the same plant, but self-incompatible. Meaning that pollen from a different plant has to be available in order to achieve fertilisation. Holly is dioescious. One plant carries male, pollen-providing flowers and a different plant carries female,
pollen-receiving flowers.
Coming back to primroses... they are Heterostylous. Heterostyly means that there are two forms of primrose, distributed roughly 50:50 across their habitat. There’s the ‘pin-head’ primrose and the ‘thrum’ primrose. The pin-head primrose has short, pollen producing stamens and a long, female stigma. The thrum primrose has a short, female stigma and long, pollen producing stamens.
Now picture this – along comes a bumblebee searching for nectar. The bumblebee lands on a thrum primrose and it reaches deep into the flower. Unbeknown to the bumblebee, the long, pollen producing stamens of the thrum primrose deposit pollen on a particular part of the bumblebee’s body. The bumblebee flies off to another flower which, as luck would have it, turns out to be a pin-head primrose. The pollen from the thrum primrose is in the perfect place on the bumblebee’s body for it to be deposited onto the long, female stigma of the pin-head primrose. We have successful cross-fertilisation.
Incidentally, the short stamens of the pin-head also align with the stigma of the thrum primrose.
Things don’t always turn out perfectly. Our bumblebee may visit numerous pin-heads before it lands on a thrum, or vice versa, and some pollen will go astray. But hey, what a wonderful thing nature is, don’t you think?
Grab a magnifying glass and check out a primrose near you.
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