Trying to be a tree

Here is a living example of the plant on which I found the dead ants -- see today's photo in my 365 album:
http://365project.org/mcsiegle/365/2013-07-25
I don't know what these plants are, but I detest them. This one is in among the irises and day lilies. My laissez faire attitude (really just laziness and procrastination) has resulted in many, many undesirable things trying to take over my yard. If I left it, this one would continue to grow.Once I had one that was growing into a small tree. They have a sticky quality to them and when I cut them they stink. If anyone is familiar with this plant, could you let me know what it is?

[Scott]

No clue what it is... sorry.

[Alicias]

Hmm.. it looks rather invasive. I'm not sure what it is either. But I can see why you would want it out of your garden.

[Kitti Nelson]

I'd take a photo or phone shot to one of your local garden centres or the botanic gardens and ask them - some type of contact poison might be what's killing the ants - would be worth making sure it won't harm anyone else.