sedges + flower

Here is a series of sedges. any help? my books dont help me much here. also the last two pictures are of one flower that my newcomb's wildflower guide doesn't have the yellow flower - ideas there?

 

Last one might be a Potentilla.

 

You could try the key in the Flora of North America for the sedges, though it won't be easy with 480 species: http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=105644

Agree with Potentilla for the last plant.

 

Are those petals or bracts on the cinquefoil?
I'm not sure, but it may be potentilla norvegica, rough cinquefoil.

Look at; Scirpus atrovirens, Dark Green Bulrush for the first sedge.

 

Looks like sepals, after the petals have finished and fallen, to me.

 

"Sedges have edges" (for the most part) other than that you will need to consult a technical key and examine the fine details to know what they are for sure.

 

alright, i found a cinquefoil with two flowers - one with the petals on and one with them off, and this certainly is it.