Birds do it, not bees!

Posted by LindaB on Wednesday, September 2, 2009

The American species in the clematis Viornae Group are pollinated by hummingbirds. These New World birds, with their long bills and tongues, have no trouble piercing the dense plug of pollen-bearing stamens (and pistols) that jam the opening of the urn-shaped blooms like those of the seedling pictured here. They easily reach the nectary chamber at the base of the filaments, and indeed, a pair of Anna’s Hummingbirds hang around the test plot, feeding on the Viornae seedlings we are evaluating. As they feed, their beaks and foreheads are liberally dusted with pollen. At Luscher Farm we are blessed with healthy populations of European honeybees, but they are completely flummoxed by this group of clematis.

The bees seem to know there is nectar in these blossoms, but there isn’t room for them to crawl up into the flower—the bees are too big, and the stamens too tightly packed. Undaunted, the bees attempted to separate the seams between the sepals, using forelegs and mouth parts to try to pry an opening to access the nectar. I watched their efforts for about 10 minutes before realizing I should be taking pictures! During the time I observed the honeybees, I didn’t see any of them succeed in opening the sepal edges, and was surprised that the bees would expend so much energy trying. A couple of rows away, native bumblebees were feasting on a Clematis macropetala seedling’s flowers (the same plant that Killdeer’s nested under a year ago), an open bell much easier to navigate in, and a flower not exploited by the hummingbirds.

Why would so many non-native bees be trying so hard to crack these clematis blooms? I did detect a slight fragrance, but there are many easier plants to drink from nearby. If these bees are ever successful at opening clematis in this nontraditional way, I’ll let you know.

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