We’re halfway between spring and summer here in northern New Jersey. Spring flowers are still blooming, but the first summer flowers have begun to open. One of our loveliest shrubs, grey dogwood (Cornus racemosa), is just coming into bloom, and the last of the local viburnums, arrowwood (V. dentatum) is in full bloom. In wet areas you will often see these two shrubs side by side, perhaps because they bloom simultaneously and can therefore share the services of pollinators.
I often wonder why certain plants so often occur together in nature–dogwood and viburnum, goldenrod and aster–there’s a pair of each for every type of site. I also wonder why so many shrubs have large, flat flower clusters made up of many tiny white fragrant flowers. Obviously that type of flower is attractive to pollinators and results in a large number of fruit. But why white flowers? why fuzzy? Viburnums, dogwood, elderberry (Sambucus species), serviceberry (Amelanchier species), and chokecherry (Aronia species) all have similar flower clusters.
Something equally wonderful but not as mysterious is the annual appearance of spring azure butterflies (Celastrina ladon) just at this time, when dogwood shrubs are blooming. These tiny creatures (wingspread of barely an inch) are silvery blue, and they flit so rapidly and so erratically that it would be impossible to photograph them, but you can see a picture here. The reason they appear right now is that their larvae feed on the flowering parts of dogwood and other shrubs. When the shrubs flower, the adult butterflies emerge.
So that seems quite simple and clear. But there were no dogwood shrubs here before I planted them. How could it be that these tiny, delicate creatures immediately found their preferred larval food source almost as soon as it was available? Every year at this time, I am filled with wonder.