I create projects for Primary Schools and these are free for schools to download and use. I want to help schools create Bumblebee 'walls'. This will be hanging tubs/containers containing flowers which will attract bumblebees. All this has to be as low cost as possible to allow budget strapped schools to participate. So what flowers, grown from seed would be likely to be 'best value' for schools, i.e lots of flower looking good in a hanging container?
Bumble bees start visiting flowers very early in the season so appreciate snowdrops and winter flowering pansies, primulas and other early nectar plants, some of which would make good winter window box subjects.
Found this list on a bumble bee help site - http://www.bumblebee.org/flowerlist.htm which should give you some ideas for summer baskets and planters.
Thank you Obelixx that is a useful list since it gives colours and sizes as well as flowering months.
Lots of annuals are good (quick) for kids and bees like then. Echiums,they're like viper's bugloss in the above list but shorter and an annual. Last year I grew a nemophilia called 'Total Eclipse' nearly black with a white edge. Not much to look at and I almost dumped it then noticed it was covered in bees. Borage is on the list I see. If you can do any cadgeing of sedums (a parent?) it would be very cheap and bees and butterflies love it. Most single flowers are useful so a cheap and chearful packet or two wouls go a long way. You can get annual wildflower mixes.