One of the things we do at work is to count airborne pollen and feed the data into the national network based in Worcester.

http://www.scri.ac.uk/webfm_send/836

The spring counts started last week, and already you can see changes. To start with hazel was dominating (in recent years our start in mid-March has missed much of the hazel flowering season), but through last week both alder and yew built up and are now the most abundant types. The alder in flower so far is the introduced amenity Grey alder (Alnus incana) rather than the native species. There were also a few airborne pollen grains of willow starting late last week, showing that the local trees have started flowering.

best wishes

Gavin