Is this bidens?

turmeric

Do you think this is a type of bidens and if so how should it be pruned?  It seems to have formed a 2ft high mound (flat on one side) of feathery leaves and the small yellow daisy-like flowers have just gone over.  I've trimmed the dead flowers off today for my neighbour but she asked if it should/could be cut back hard to improve its shape.

I've just noticed that the flower buds are too blurry but they were like bright yellow daisies if that helps at all.
Many thanks.

Borderline

I suspect they might be Coreopsis Verticillata.

turmeric

I've looked it up Borderline and I think you're right.  My only reservation is that the flowers were quite small (1.5cm?) and the ones I'm finding online seem at least an inch (sorry for my inconsistency with metric and feet and inches, I'm of a certain age..!).  But perhaps there's a coreopsis with very small flowers.  Thanks again.

Borderline

I'm not really familiar with all of them. I have grown one many years ago that was only about 3cm in diameter. They are not long-lived plants and do need a lot of drainage. I can't think of any other plant with foliage like that right now. 

turmeric

Thanks Borderline.  The foliage definitely matches, I'll do a bit of digging to see if I can find one with smaller flowers.