What's Your Name?

I picked up some of these plants at the Master Gardener spring plant swap last spring. Seems like eons ago. I don't recall any name on them, but they ended up being planted in the way-back -- mostly sunny, some shady area without much good soil. I am slowly building up the soil in this plot with more organic material in hopes of growing additional perennials.

During the fall (last year) they reached a height of about 3 feet (1 m) and bloomed near the end of summer. They dutifully popped back up this past spring, then towered to 6-feet tall (2 m), much higher than I was expecting.

The leaves are partially lobed, lacy, thin, somewhat palmate, a little like oversized cosmos, and nothing like sunflowers or any other helianthus I know. The blossoms are pure yellow, similar in size and appearance to double-flowered coreposis, around 1-2 inches (3-5 cm). But coreopsis does not grow this tall. Nor do coreopsis leaves look like this. Japanese kerria is similar, but this is not a shrub, nor do the leaves match. No fragrance. Dry conditions do not bother it much, and there are no signs of disease or insects. However, powdery mildew is beginning to show up.

They die back to the ground in winter. They have continued to bloom over the past month but are beginning to slow down. I previously thought the stalks were strong and sturdy, but a recent rainstorm knocked most over. They were strong and straight while growing, but once the blooming started, they could not stand up to wind and rain.

Are they in the coreopsis family? Are they a form of helianthus? They seem happy where they, so they will remain there.

For The Record:   • Clay soil with a little organic mulch   • Mostly sun but some shade   • Small amount of fertilizer   • No serious pests/disease   • Tend to fall over when fully grown