fennel

I've heard that Fennel attracts butterflies, so I moved a plant that always got mowed over, into the garden next to another one. They're on the outer back edge. Growing strong. But I just read on another gardening blog that fennel is invasive- so it's better to have in a pot. When I walk over to the spot where I dug up the second plant, there are small fuzzy plants all over the place. Now I'm thinking I shouldn't have moved that plant, and I ought to dig them both up and put in pots, instead.