Bob Hobden pretended :

We used to leave ours in as long as possible so they flowered when we
had bee keepers on the allotment site as the bees love those flowers.
Unfortunately the bee hives have gone now so there is little point.

Funny you should say that, as I have found out since letting them go to
flower, they are real bee magnets, of which I am very pleased to see.
Over the past couple of weeks I have been so pleased to see so many
bees in the garden as last year when we were in drought (our area is
still drought declared) thousands of bees died and the bee industry was
hard hit. However, at the moment, it looks like the bees have
recovered. Apart from honey bees (introduced), I have seen many of our
native bees. My husband has made a few bee "homes" and we have them
placed around the yard, there's been no takers yet, but time will tell.
Most of our native bees are solitary bees, they don't swarm and make
hives like honey bees.