Mom wasn’t kidding at the time; the bees (small bumblebees?) were absolutely loving the Senna hebecarpa flowers! Catching photos of them was tricky with their speed.
It was a mystery to me as to why this flower is such a bumblebee favourite, but while doing research on seed germination for this species I learned a neat fact to explain it;
S. hebecarpa does not produce floral nectaries! Bees actually gather around these flowers for the protein-rich pollen, not for nectar. Explains why the majority of the bees that were swarming the flowers were Bumblebees