Himalayan Balsam (Impatiens glandulifera) provides a big hit of late summer nectar.  The speckled pattern guiding pollinators into the heart of the flower is clearly visible in the photo above. Bumblebees in particular forage on I. glandulifera in which case you can only see their backside sticking out!

 NB Himalayan Balsam is regarded as an invasive menace by many (though not all) ecologists. I won't revisit these arguments here but I have written about them in previous entries on this species.