Does anyone know what this flower is called? I bought from a nursery in San Diego and the lady who sold it to me had no idea. I am doing something wrong because, as you can see, it is taking a turn for the worse. Trying to figure out more detailed care instructions, and any help identifying it would be greatly appreciated. Thanks!
it is a cactus dahlia http://davesgarden.com/pf/go/64306/index.html http://davesgarden.com/pf/showimage/42728/
Since the photo is sideways it is hard to tell what decline you are referring to, but if you mean it is drooping, I'd guess it needs water. That is a lot of plant for what I imagine to be a 1 gal pot, and probably needs water daily especially if it is in a lot of sun. But also, a plant purchased in full bloom has nowhere to go but downhill. It has reached its glory point for the year, and unless it has a lot of new buds forming, the part of its life cycle that you get to watch is the flowers fading and the petals falling off. However, in your zone I think Dahlias are probably perennials that you can leave in the ground year-round, so you will get to enjoy the whole show next year. In colder climates people dig up the tubers and store them for the winter.
Foliage looks OK, browning of individual flowers just natural aging and dying of those. Snip these off. Kept watered, fertilized and staked as needed should grow and bloom for months. Up here dahilias grown from tubers planted in ground bloom late summer to hard frost, at which point tops die off and tubers are dug and stored indoors until planting out again in spring (some get left in the ground by those willing to chance it). Don't know what the routine is down there, perhaps they even bloom most of the year.
