Another plant growing in the Bee & Butterfly bed that the white-tailed bumblebees enjoy is Allium Sphaerocephalon. These unique flowers open green, then start to turn a purple/crimson colour from the top, creating unusual two-tone drumstick flower heads. Unlike the larger alliums which flower in May/June  these flower later in the year around July/August. I planted these in the autumn 2018 and loved them so much that last autumn I bought more to plant in one of my other raised beds. They reach a height of 60 cm and sway in the breeze, though they do require some support from other plants otherwise they can topple over. Nice amongst tall grasses I imagine.