I note you already have cotoneaster horizontalis on your list; I can only add that, this spring, mine was absolutely covered with tree bumblebees, to the exclusion of other varieties. I wondered if this relative newcomer was excluding other bees from visiting this plant?
Hi, having trawled through my records for the past 3 years, here are some flowers B. hypnorum has visited that are not yet on your list;
Clematis alpine (blue and purple), rosemary, crab apple, dog rose, hebe, Cotinus coggygri, Salvia purpurea, Astrantia, Teucreum (Wall germander), pyracantha, rosebay willow herb.
This year I began to keep records about the types of flowers bees are visiting so I am pleased to have the opportunity to use some of this information already!
So some additions to the list
Bramble - Rubus sp
Figwort - Scrophularia nodosa
Herb Bennet - Geum urbanum
Lousewort - Pedicularis sylatica
Oil Seed Rape
Just seen a B. hypnorum queen foraging a cardoon flower; also pollinating my blackberries.
Himalayan honeysuckle (pheasantberry), and horse chestnut - not seen any for a while , in contrast to other years when tree bees and common carders have been the two species still active in late summer.
Hi Clive a popular plant for my Tree Bees that I don’t see on your list is the Spirea
B.hypnorum workers collection pollen from Sweet briar wild rose in my garden. You can hear them buzzing loudly when they are in the flower - buzz pollination. Also pratorum workers using this rose.
Another one:- foxglove