AnnMarie's Blog

Some of our tulips are now out, merrily opening & closing their blooms according to their own schedule. What is it that drives this schedule?

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The tulips  have their own biological clocks built in; this is what drives the circadian rhythm of flower opening & closing. The tulip’s clock is reset everyday by the rising of the sun; the tulip can also move its position with the sun. This is photonasty or the tendency to physically respond to light stimulus. The tulips also demonstrate thermonasty, a response to temperature; tending to close up with a fall in temperature. Thus on a warm bright morning the tulip flowers open up beautifully but as light & temperature drop in the evening, they close their blooms again. Why have they evolved to do this?

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The tulip flower is insect pollinated and the tulip advertises with both bright colours & scent from volatile oils. The picture above shows the male & female structures, with much pollen in evidence. To remain open overnight is to both risk damage from the weather & to waste volatile scents, whilst it’s insect pollinators are not around. Thus a tulip increases its chances of successful reproduction by closing it’s blooms at night. Many flowers show this behaviour and conversely, for example, bat pollinated plants often only open their flowers at night.

Plants also use biological clocks to sense various other things such as opening leaf stomata just before dawn ready for photosynthesis and by monitoring day / night length they can tell whether its flowering season or not.

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I want to transport you to a seedy, or perhaps I should say nutty, region of reproduction. A place where the male structures are vast in comparison to the petite & flushed female variety. But first, do you recognise this flower?

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Yes, its a female Hazel (Corylus avellana) flower and that’s the region I’m talking about the spring hedgerow.

The male flowers, that we often call catkins or lamb’s tails are borne on the same tree as the females and are left to hang in the breeze, thereby distributing pollen on the wind.

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It is normally February when the catkins open, they first formed back in October or November last year. The male catkins are typically 5cm long, possibly up to 10cm; yet the female flower is tiny with the crimson stamen measuring only 2 – 3 mm. Pollen, carried on the wind, lands on the sticky stamen & fertilises the flower. Note: Hazel is not self pollinating, pollen from a different Hazel tree must fall on the stamen for pollination to take place

Nut clusters will now form at the site of the female flower, ripening in autumn. These nuts are a valuable feed source for many creatures (ourselves included); indeed the hazel relies upon this fact so that animals like squirrels will collect, horde, & loose nuts. This disperses the Hazel’s seed & helps to guarantee a new generation of Hazel trees.

Hazels are a member of the Betulaceae or Birch family. As well as producing edible nuts they have been used in various woodcrafts for many centuries. Wattle hurdles, Hazel walking sticks and Sheppard’s crooks are a few of the uses. The nut shells have recently been discovered to contain useful anti-cancer drug components. Environmentally Hazels are known to be important members of British woodland, they support many lichens & fungi, their leaves are good food for deer and the nuts I’ve already mentioned.

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The image above shows Hazel Pollen imaged at x200 magnification with a light microscope.

Trivia: In Celtic myth the Hazel is believed to collect knowledge & wisdom in its nuts, those who consume the nuts may inherit the wisdom.