What are they doing here?

The other day, I walked down the side of the house by Tony and Kelly's (the east side- the wedding entrance side) where those big plants are.  I heard a lot of buzzing and saw lots of bees.  I looked at the plants, but there were no flowers.  Then I saw the bees were landing on the underside of the leaves near the petiole.  Of note, they were only landing on leaves in the shaded area. 

Resin on a bees leg

What were they foraging for, I wondered.  I thought at first they might be collecting resin or or some of the cuticle for propolis.  Bees carry their collected resin back to the hive in their corbicula like pollen, so I looked at several bees but all their legs were bare.  One theory disproved.

 I watched carefully to see what they were doing on the leaves.  They actually were using their tongues on the leaf, and they were only going to the base of the leaf.  So, naturally, I licked some leaves- sweet!
These plants must excrete a nectar. A little online search and yes, theory confirmed.  I found a lot about extrafloral nectar secretion and observations regarding insect behavior relating to it.
 I don't know what kind of plant we have, but I'll take a branch to a nursery for identification.  Isn't nature amazing?