Unknown plant - help

Can anyone identify this plant? I evidently bought it 3 years ago, and it has come back every year, but has never blossomed. Last year it grew to about 2 ft tall. This year it is already over 6 ft. I thought it was a columbine, judging from the leaves; but now I know that can't be. There are three of these planted in a square planter and I probably bought them to cover up the electric meter on the side of the house. See photo of the top (which looks like blossom buds but just continues on as another set of leaves) and another photo of the leaves themselves at the base of the plant. A third photo shows the plant from about 8 feet away against the side of the house -- to give you some idea of the size it has grown so far this year -- and it's only May!

Second photo of unknown plant

Third photo of unknown plant

Leaves at base of unknown plant

Looks like some kind of Columbine. BEV

Are you sure the leaves at the base go with the top part and it's not two different plants growing together in the same place? In the third picture down, I see some other leaves on the mystery plant that look nothing like the leaves at the base. And while the leaves at the base do look like columbine, what you show in the other pictures does not.

It reminds me of Thalictrum delavayi http://www.robsplants.com/plants/ThaliDelav.php. I had a plant and the garden service decided it looked like a weed and pulled it. I was so upset - went looking for it on the compost heap. Found some Aquilegia plants that went the same route, but not my Thalictrum. I am green with envy.... I would so love to have one in my garden.....

Enjoy,
Elsa

Sure it could be a Thalictum. There are quite a few species and hybrids available. Maybe yours is Thalictrum aquilegifolium. You will get a better idea after you see it bloom.

I see clematis leaves on the trellis. BEV

Yes, the bed has some other plants -- clematis is one, but there are others. Ignore those.
Trust me -- the leaves that look like columbine do indeed go with the plant that is now nearly 6 ft high and has what appears to be tiny green buds at the top. In a day or two these will become another set of leaves, the stalk will grow another 3 inches, and a new set of these tiny buds will form -- they remind me of a poorly developed head of brocoli.

No blooms? I have meadow rue in my garden. This is what the flowers look like, colors vary.

You can see the leaves here.

The leaves are definitely columbine, but the flower head looks like when Echinaceas get infected with Aster Yellows.

http://www.forestryimages.org/images/192x128/5382053.jpg

It's a phytoplasma that infects a wide variety of ornamental and commercial crops. The symptoms can manifest themselves in different ways, but one of the most recognizable is the proliferation of multiple flower heads that remain green and never mature.

There's no way to tell for sure if this is it other than an expensive test. If I saw what you have in my garden (and couldn't ID the plant) I'd rip it out and not plant anything susceptible to Aster Yellows in that spot for a good long time. There is no treatment besides ripping out the plant, and do NOT throw it in your compost.

Thanks to hczone6, here is a photo of Meadow Rue/Thalictrum aquilegifolium in bud. This is a very dark-coloured one, but a white one would of course have pale buds.

http://davesgarden.com/guides/pf/showimage/16163/

Six feet is very tall for an Aquilegia. I do not know of one that tall. It's tall for a Thalictrum too, but I've had some other T. species top out over seven feet.

http://www.umassgreeninfo.org/fact_sheets/weed_herbarium/pages/thcpo.html

http://davesgarden.com/guides/pf/go/102988/

OK, thanks to all -- the mystery is solved: The unknown plant is
Meadow Rue, Thalictrum -- in this case not aquilegifolium but glaucum,
which gets yellow flowers. I think I got it from Bluestone Perennials as
a three-some for $15 or so. This was in 2007. In 2008 it was only about
2 ft tall and had no blossoms. I now measured it at 5'8" and it seems full
of buds. We'll see what happens. Evidently it is a hardy little (?) guy; and,
according to the Bluestone catalog, it grows to 5 ft. I recall buying it in order
to cover up the electric meter on the side of the house. (Creative landscaping?)

Again, my thanks to all who responded and offered help.