Are you sure the first one has yellow flowers? Because it looks awful a lot like Glechoma hederacea, I might be wrong though.
Asteraceae are difficult but not so scary when you get used to it. Andre, your way of lumping together the pictures may save some space but it would be much easier for identification if they are presented with more resolution. Peering into the details of the flower, I can probably recognize the double envelop of phyllaries. Internal, ascending, and external, reflexed. This is one of the key features of Bidens. It woulld help if you split the ripening head and see the shape of the achenes, which in Bidens should have two or three sharp spikes at the top.
Sorry for the multi pics but this is much easier from my iPhone. Does this pictures help to identy my DYC ? ;-)
There are few features of Heliopsis that are not seen in this plant: - Receptacles mostly flat to convex or conic - Leaves opposite, petiolate - pappus missing or coroniform Here we have fairly flat receptacle, alternate leaves, pappus in form of sharp awns (they are clearly seen in the open head). This could be a Bidens or Coreopsis, two related genera. I am not sure that FNA lists all European and garden species, but the list includes several dozen species for each genus.
Thank you Andrey for your answer. Regarding the pappus, I can't see the two teeth (which is the translation of the the latin bi dens). Maybe they will appear later. For the Coreopsis, I can't find any corresponding leaves on all these pictures. What about Cosmos ?
Cosmos has fewer florets (10-20) and opposite, 1-3-pinnatifid leaves. I zoomed the last two your pictures to show the awn-like pappus. The fact that the awns can easily fell off makes me doubt that this is true Bidens. The search engine usually presents the most popular links. If you don't specify a particular species name, the pictures may never appear among the selection.
While that is somewhat true, I highly doubt that any species of Bidens or Coreopsis is this robust looking. While I'm truly in problem with these yellow flowered plants, I believe it may be some kind of Helianthus. There are pretty similar species of Helianthus, at least (not to even speak about the hybrids). http://luirig.altervista.org/schedenam/fnam.php?taxon=Helianthus+tuberosus http://alienplantsbelgium.be/content/helianthus-decapetalus http://farm4.staticflickr.com/3517/3862432624_a9ed5383e6_z.jpg
Yes it looks close to Helianthus. Usually this plant grows up to 6 feets tall (but not this year because of very bad weather). The big differences with tuberosus are : - the flowering. The DYC is flowering since mid august and the tuberosus is not yet flowering. - the stalk of the DYC is much thinner than tuberosus. - Resistance to oïdium For comparison, here is an Helianthus tuberosus leave close to the DYC ;-)
I think it may be a good possibility. Not necessarily H. tuberosus - there are about 50 different Helianthus species. This photo demos Helianthus pappus very similar to the DYC. http://www.flickr.com/photos/plant_diversity/5020916476/
Yes, I know that it's not necessarily H. tuberosus, I was just trying to point out the similarities of the DYC to certain Helianthus species. Actually, a few weeks ago I took some shots of a plant that looks really similar to the DYC in question. It was definitely not H. tuberosus as although both was in bloom, H. tuberosus was a much bigger plant by that time. Unfortunately that plant was just labelled as "roughleaf sunflower" (translated) which might be basically anything.
Even DNA may be ambiguous. Recent progress in plant sequencing reshaffled the entire plant taxonomy. And this is only the beginning. Until then, it is still possible if you manage to go through the complicated key for Helianthus (http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=114871). Anyway, if you take a look at this key, you can figure out why it is practically impossible to make a positive ID with just a photograph. Tiny, sometimes even microscopical details are needed to make you way in this labirinth.
