Saturday, 12 February 2011

Catkins

I have already mentioned the Hazel catkins which are decorating the trees right now, but there are more catkins to be found.  Some of the more common are those belonging to the Common Alder (Alnus glutinosa).
The dangling catkins are, as with the Hazel, the male flowers.  The female flowers are smaller, more rounded and resemble fir-cones.
Alders grow in moist soils all over Europe and are a great favourite with several small members of the finch family.  Especially Siskins and Goldfinches.  Belonging to the same family as the Birches, they grow to around 60-90ft, very rarely over 100ft, but mostly much smaller.  The roots of the Alder tree engage in a symbiotic relationship with a nitrogen-fixing bacteria called Frankia.  This relationship enables the tree to obtain nitrogen from the soil, while the bacteria are 'fed' with carbon from the tree itself.  The nitrogen-fixing quality of alders (rather like members of the pea family), naturally fertilizes the soil surrounding them and therefore is very important to other plant species.
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