Paul. Mullein and mugwort are two different plants. Mullein (Verbascum thapsus) is a biennial and Mugwort (Artemisia vulgaris) is a perennial. Mullein has a spike of tightly growing yellow flowers. Mugwort has very tiny whitish flowers. Neither is what you have. It looks like you might have something in the lettuce family.

Take it to a nursery, or to your local agricultural authority, or to a horticulture school, or to your botanical gardens for expert identification.

Don't even THINK about using it it any way until you know with absolute certainty what it is.

herbalbetty is right. Mullein has some fuzz on the leaves. I hope this is of assistance to you.

Paul - I believe you do have a mullein there, ie it IS a Verbascum, but not V. thapsus. I can't tell you which one because I am not familiar with US plants. As HB says mugwort is a different plant entirely. I suggest you post your pictures over on the 'Name that plant' forum here on GW where someone will almost certainly id it for you.

Looks like Moth Mullein, Verbascum blattaria, to me. See what you think.

FataMorgana

Here is a link that might be useful: Google Images - Moth Mullein