Yellow Flower ID Please

[Peter W]

Can anybody help Id these yellow flowers? The plant is growing near where the Hogsmill River joins the Thames at Kingston. To try and pretty up the concrete culvert it runs in, the local council have constructed some submerged planting containers and stocked them mainly with native water loving plants. I know most of them except this yellow plant. I'm fairly sure it's not native, but if it's a cultivated plant I haven't a clue what it is. The flowers have eight petals each ending with three points. Thanks.

Peter

[Jez]

They look very Dahlia like to me!

[Peter W]

Quite right they do! I had thought of this but as far as I know dahlias do not grow in water and their petals are usually entire rather than divided in three at the tip. Leaves aren't right either.

[Jez]

I was also wavering on Coropsis. What do you think? Some like damp situations and I can't see Dahlia's being tuberous plant's liking the same! Hoping for input from the regular Plant masters/or anyone who knows, as I do feel a wee bit with no certain answer!

[aeshna5]

Maybe Bidens cernua var. radiata which is an uncommon form of Nodding Bur Marigold.

[Tiggrx]

Originally Posted by aeshna5

Maybe Bidens cernua var. radiata which is an uncommon form of Nodding Bur Marigold.

That was my first thought, but both leaves and flowers are wrong.

I shall look through a few books...

[Tiggrx]

Niger (Guizotia abyssinica) could be a possibility?

[aeshna5]

Originally Posted by Tiggrx

Niger (Guizotia abyssinica) could be a possibility?

Does look good for this. I've never managed to see this as a casual, but know it reguarly turns up. I even scattered a lot of niger seed in my garden as the goldfinches stopped using it, but seeds must have been void as none emerged unless they are particularly palatable to molluscs!

[Peter W]

Many thanks Tiggrx, I've now found some fairly good picture matches for my pic. against Niger on Google.

Peter