Unknown plant at pond edge

Observed by IWoodwardIWoodward's reputation in PlantsIWoodward's reputation in PlantsIWoodward's reputation in PlantsIWoodward's reputation in Plants on 2nd February 2013
(Added to iSpot on 7th October 2012)
Woodford Golf course poss composite 2012-10-07 4
Woodford Golf course poss composite 2012-10-07 3
Woodford Golf course Bidens achene Oct 2012 (3)

In mud at edge of pond

Location: A1009, London
Identifications
Species interactions

No interactions present.

Other observations of Trifid Bur-marigold (Bidens tripartita)

Comments

Fruits

8 October 2012 - 10:38am — cicuta58
Botanical Society of the British Isles
Plants expert

I agree this is not B. cernua and could be tripartita var intergra, but these days you need to consider B. connata which has warty achenes as opposed to smooth ones. It is, however, usually by canals.

cicuta58

Thank you both

8 October 2012 - 12:01pm — IWoodwardIWoodward's reputation in PlantsIWoodward's reputation in PlantsIWoodward's reputation in PlantsIWoodward's reputation in Plants

It seemed too small to be a Bidens (only about 50mm tall). I will try to get back a couple of times over the next few weeks to see if it grows any taller and to check the achenes.

EDIT February 2013

6 February 2013 - 4:48pm — IWoodwardIWoodward's reputation in PlantsIWoodward's reputation in PlantsIWoodward's reputation in PlantsIWoodward's reputation in Plants

Entry edited 06/02/2013 to add a photo of the achenes (achenes collected late Oct/early Nov 2012 and photographed on 02/02/2013).

Achenes appear to support ID as Bidens tripartita - more or less flat with 2-3 bristles, tapered from apex to base, backward pointing barbs on both the achene and the bristles.

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