It can be very difficult to know which flowers are favorites to hummingbirds. You can have a yard full of Geraniums and frequently see hummingbirds show up to them, but it doesn't mean they top their list. If the Geranium is the best of what you've got in your garden then it will appear like the best flower for them to feed from, but not even close to the best in food value. Over the last few years people have listed their favorite hummingbird flowers on my website. I'm very surprised at times at which flowers are mentioned, and at other times it's confirmation of just how good certain flowers are. I suppose a lot has to do with the amount of time someone has been attracting hummingbirds. If you are new to attracting them, then there are a number of flowers that you should just not do without. That list of flowers can vary greatly depending on the region or climate you live in. In a recent post I gave some ideas of perennials and annuals that are really effective. Today I wanted to mention that it's a good plan to always add a few new varieties each year. Change it up a bit and try half a dozen new flowers each year. See how effective they are and decide whether to continue them in future years. Test them for hardiness, how much attention they deserve or need, how well they flower and ultimately how much hummingbirds like them. Like I've mentioned in a past post, plant heavily on the effective one's. Over the years you will develop a garden that requires the least amount of effort with the greatest rewards and the most hummingbirds. Some people may question why I would suggest flowers that require the least amount of effort, but it starts to make sense as you expand your garden and repeatedly have to give attention to certain flowers that just don't produce well. There's enough work to be done without having to give special care and attention to that one ornery flower that won't produce as you wish. I only wish Foxgloves would do well in my garden but every year I lose 75% of them and the other 25% do very poorly. They are a hummingbird magnet but have been scratched off my good list for a few reasons, mostly because they don't survive in my climate or soil. This is one reason I love to start plants indoors from seed. It's extremely cost effective to plant some new perennial varieties from seed each year. If you lose them over the first winter it's no great loss. Again, here is a page on my website that will give you an idea of flower choices for hummingbirds. http://www.therubythroat.com/flowers.html
Here is an image of a young Ruby-throat that found great value in a Himalayan Balsam (It's considered an invasive species in some regions). Hummingbirds like them even though it takes a bit of monkey work to get to the nectar. If you look carefully, you can see the little razor talent pierced through the petal. After a while the bottom petal of each flower became shredded from the intense feeding.
N.E. of Edmonton, Alberta, Canada. August 2017. Juvenile Male Ruby-throat hummingbird.