I wonder where these bumblebees are feeding now, there's very little growing in the 'wild' here.
I often wonder too, also over here there is hardly anything blooming in the wild.
And yes, single or semi-double flowers are essential for the polinaters, fortunately I don't like flowers without a 'heart' so i don't have any double flowers.
In my garden, I still have many blooming to the joy of my bumbles like Dahlia, Alstroemeria, Asters, many Fuchsia, Begonia, Cyclamen persicum, Viola cornuta, Salvia microphilla, Lobelia erinus,Bacopa, Trycirtis 'Toyen' that blooms for an amazing long time, your Geranium Yeoi, which still produces flowers so late!
etc.. none of these are native.
From the many natives I have only a few are still blooming: Cymbalaria muralis of which I have plenty, a few Geranium robertianum and Cyclamen neapolitanum.
A very interesting non-native blooming is Rabdosia longituba that is blooming for the first time,
it only starts flowering from mid-October!
As I have a small enclosed town garden, in the summer and spring I still have quite some sun, but as the sun sinks later in the season, I hardly get any, in the winter even nothing.
I need a lot of long blooming shade-loving plants for my bugs and for my sanity too!