Identify This Plant - Ambrosia trifida, giant ragweed

Hi All! Could someone please help me identify this plant? I've never seen this plant before in my garden. It's only in one small area. It is possible I planted this from seed in spring. I collect seeds from around the world, so I'm thinking it could be an exotic. Just can't remember. It stands about 7 feet tall, has single and multi lobed leaves, the seed or soon to be flowers smell like lemon. It's covered in black ants, but I don't see any sign of aphid herding. Any suggestions would be appreciated. Thanks

I believe it is Ambrosia trifida aka giant ragweed.

Cortland, Thank you. That's what it is. With your help ... I found the original seed package. I think this was an added freebie from an over seas seed purchase many years ago. Most likely for medicinal purposes. I've been pulling common ragweed, (which showed up this year) all season. I think I will save some seed, maybe make a tincture. I'm obviously not allergic to it since I've been crushing it and sniffing it. But, before it drops its seed, I'm gonna pull it all. If it's as prolific as the common ragweed... its gotta go. Thanks again for your help.

Rick,

Your welcome! I am allergic to rag weeds, so I do have a keen eye for it!