Each year the Phipps Consevatory’s exquisite Outdoor Gardens changes its offerings. 2012’s plantings were wonderful. For several weeks my morning visits saw no butterflies at the large groupings of these verbena. Yes they were a vivid red, a color that is usually guaranteed to draw lepidoptera. Yes they were expertly planted and massed, mulched and in sunny beds. Surely they must be producing nectar, don’t you think?
Yet no butterflies, until the 3rd week in August. Taddah! That morning butterflies of several species were at the verbena, methodically moving from flower to flower, not rushing. Apparently most of these individual flowers was pumping-out sugary nectar.
Our female Danaus plexippus is feeding contentedly, even tolerating my macro- approach to within about 12 inches. She may well be preparing her eggs and appreciating the abundant nutrients in this nectar/pollen cocktail.
Back to the issue at hand, the verbena appeared to be lush and healthy, but brought no butterflies for several weeks. Then they became a magnet for hungry butterflies. What changed? Why? Anyone?
Jeff
Winged Beauty Butterflies 
If they had continued to ignore the plant I would have said the plant was developed for its beauty, not nectar. Insects prefer natives because they have evolved together. My second thought is time of day. The nectar can vary throughout the day. Another possibility is that the nectar could have been drained earlier. Perhaps the flowers you saw were already pollinated.
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What changed? The weather. In early August, it should be warm enough. In
the same way, you see hurricanes in August and September because the ocean has warmed sufficiently.
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