Hi. This plant grow to 50-80cm high. It looks like a Veronica longifolia 'Alba', but I think it's not? The bumblebees loves it Thanks.
It's hard to tell without the foliage, but it could be Culvers Root Veronicastrum virginicum (Culver's root)
Yes, that's the one. Next time I will remember to take some pictures of the foliage. I was so busy to follow the bumblebees Thanks for the help!