We have Monarda (Bee Balm) which runs everywhere. My neighbors love my front garden... they call it the WILD THING...LOL It has so many perennials that have multiplied and spread to opposite side of the garden and into their yards too..

I bought seeds for a "black" columbine. It came up and grew and reseeded all over. Only problem I hated the flower, nearly black with some white. I keep pulling out plants when I found them but couldn't seem to keep ahead of it. Four our five years ago, some out-of-town friends were visiting and say it and commented on wanting some. I gladly gave them a trowel, come potting soil and plastic bags. They were very diligent and got took all. Yes, I saw it in there garden; they love it. I've managed to finally get rid of it in years since. One person's weed is another person's treasure.

OOPS, double-posted when I meant to edit my first post.

I have that too. The Humming birds love it. But it doesn't stand up it just flops all over and smothers the smaller flowers in front! The roots go all over too!

I have an Ivy type of plant that a neighbor long ago gave to me & I cannot kill it or get rid of it. It has taken over the flowerbed! Two yrs in a row, we even dug up the flowerbed & thought we got rid of all of the roots, but it came back with a vengeance! It spreads like wild fire. When you rub the leaves, it smells like an orange. We've even sprayed it will Roundup trying to kill it & had no luck! Wish to goodness I knew what it is called.