Sorry but I couldn't resist blending two neighboring messages. In my case
I'd
have to say Japanese Climbing fern, with Cat's Claw as a close second.

The Weed of the Year award goes to Pokeweed again this year with a close
second of Giant Ragweed. The pokeweed took over the back yard around the
shed to dizzying heights of 7 feet -- since the area was already elevated a
solid 3-4 feet (retaining wall & patio) that 7 feet looked even more
impressive.

James