Hawkweeds - Hieracium agg

Hawkweeds Hieracium agg are very difficult for the casual botanist to sort out into species. In fact they are an aggregate of hundreds of microspecies which do not hybridise and reproduce without pollination. No ordinary field guide will go into detail about them and so they are generally just identified to genus level. The Field Flora of the British Isles by Clive Stace allows you to key them to 15 groups of related microspecies. If you want to take the identification further you will need the achenes (plumed seeds) and some specialist literature. In addition, Hawkweeds are easily confused with Hawk's-Beards Crepis spp, the difference being that Hawkweed achenes have buff coloured plumes and uneven overlapping bracts under the flowers; Hawk's-beards have white achene plumes and distinct inner and outer rows of bracts. They can also be confused with Nipplewort Lapsana communis, but this species has noticeably fewer 'petals' (no more than 15).

Hawkweeds all have erect stems with at least some leaves up the stems and yellow flowers with strap shaped 'petals' (as they belong to the Daisy family Asteraceae, each 'petal' is actually a floret). The achenes have a ring on top and a plume of brownish 'hairs'.

Below photos of a colony of Hawkweed on the side of a track in the Foret de Preuilly, June.

3 comments:

  1. Oh what a nice entry for a Sunday, Susan! You have obviously had difficulty sleeping... Hawksbits agg[h] [sorry... that is my term for them all! Be they Beards or Weeds or Bits they are members of the Daisy family with differences in the end of the petal, the stamens, the leaf... etc.
    White or brown pappus hair... who cares... apart from a few lime lovers which are good soil indicators, they are mainly all plants of grassy waste ground, be it damp or dry according to type, they are plants for the insomniac. Except, of course the wonderful Fox and Cubs... aka Orange Hawkweed [Pilosella auri-something] which is my favourite from this group.
    Not quite as bad tho' this group as Rubus fruitipricus agg. with it's 2000+ micro differences.
    Definitely a pair of groups for the serious field botanist with a lot of time on their hands.

    The WV is a heather... ericerma eriview

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  2. Tim: Sorry to traumatise you on your day of rest :-) They are not for beginners, but it is worth getting to know the differences between the genera.

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  3. You didn't cause too much trauma... but you did remind me of an old friend [now gone botanising to the great field] who was a Rubus specialist... I never saw him arrange his pencils according to size... but his pint and packet of crisps had to be just so to the ash tray and the next persons pint... I occasionally moved things a tad when he nipped to the loo to make more room for the next pint... and the first thing on his return was a re-alignment before the next mouthful. He was a beer "twitcher", too! But a wonderful, knowledgable man with an encyclopedia for a brain similar to good old Ted "Swan-neck" Ellis... wonderful people and I hope in this day of instant access to webinfo that people like them still exist.

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