Q.We have a plant / flower that grown and we have no idea what it is?
It has fennel type leaves but is the size of a 6 foot Christmas tree with flower buds just appearing now. The stem is round and sturdy and the is no bulb at the base.
Certified GKH Gardening Expert
The thing that concerns me is its similarity to very poisonous plants like poisonous hemlock and fine-leaved dropwort. I would take it to a local nursery or contact a university with a horticlutre department and try to get it positively identified. It could be fennel, but I'd be sure. Look over the fence in the neighbor's yard and see if you see anything similar growing.
https://wildflowerfinder.org.uk/
https://www.gardeningknowhow.com/edible/herbs/fennel/growing-fennel.htm