The Wonder of Witch-Hazel Blooming in Winter

If you are a careful observer of the living world around you, I suspect you will agree that this world is an open invitation to be amazed.  Whether we look through our own eyes, or through a magnifying lens, a microscope, or a telescope, the closer we look the more intricacy and complexity we see.  

Scientific theory proposes that life originated by chance”—i.e. by “undirected, natural causes.”  But some of us are unconvinced that chance events could have created the order and complexity of life.  A logical alternative is to believe that the complexity of creation is the handywork of an intelligent Designer.

Witch-hazel at Secrest Arboretum
(Photo:  Brad Will)

But let’s not be too distracted by the “origins debate.”  Instead, let’s consider just one example of the wonderful complexity found in the world of plants.  The plant in question is a tall, winter-blooming shrub or small tree known as witch-hazel (Hamamelis virginiana).  Did I say “winter-blooming?”  Yes!  Native witch-hazels generally bloom in late fall; whereas, hybrids may bloom in winter and as late as March.  In his Nature Notebook column, Herb Broda cites Paul Snyder, program coordinator at Secrest Arboretum (The Ohio State University, OARDC-Wooster, Ohio), who confirms that the arboretum is home to at least 50 witch-hazel plants.

Witch-hazel flowers are closely attached to its woody branches.  Each flower has four slender, bright yellow petals that can curl inward for protection during freezing temperatures.  The showy, fragrant, and nectar-filled flowers hint that one or more animal species are being attracted to accomplish pollination.  But what animal pollinator would be sipping nectar from witch-hazel flowers during winter?

For many years, scientists had been observing witch-hazel plants in bloom to determine what animal species were attracted to the flowers.  No success.  Then, two physiological ecologists, Bernd Heinrich and his mentor and colleague, George Bartholomew, took up the task.  Their approach illustrates a presupposition of “good science” and a principle of “good scientific inquiry.” 

First, “good science” presupposes that knowledge of the natural world, or creation, is discoverable.   That is, the world around us reveals itself in objective terms and invites us to come to it in order to discover its secrets.  The resulting principle of “good scientific inquiry” follows logically.   Dr. Bartholomew expressed this principle of inquiry as follows:  Become a careful observer of the plant or animal under investigation and let it “tell [you] what questions to ask.”  Because Bartholomew viewed organisms as “inseparable from their environment,” a corollary to the above principle is, “to know the organism it is necessary to know its environment.”

Bernd Heinrich applied his mentor’s principle to the question:  How are witch-hazel flowers pollinated in the dead of winter?  Finding no pollinators in daylight hours, Heinrich hypothesized that the elusive pollinator is active in the nighttime environment.  Sure enough, he discovered a number of nocturnally active insect visitors to witch-hazel flowers.  These are members of the Noctuidae, a large family of moths with dull forewings and pale or colorful hind wings (Heinrich, B. 1987. J Experimental Biol. 127, 313-332.

Next, Heinrich asked how small, “cold blooded” animals like the noctuid moths can be active in cold temperatures.  Again, by observing and letting the moths “tell [him] what questions to ask,” he discovered that noctuid moths are capable of shivering.  Because intense muscular contractions in animals generate heat, here Heinrich measured tremendous heat production by moth thoracic muscles, a process called thermogenesis.  In order for animals to be metabolically active in winter temperatures, they must either obtain heat from their environment as most invertebrates do by locating themselves in warm and/or sunny spots (ectotherms); or, they must use their own metabolic activity to generate heat within their bodies (endotherms).  The noctuid moths are considered endothermic because they generate heat by shivering. 

By initiating rapid thoracic muscle contractions at freezing temperatures, noctuid moths are able to warm the wing flight muscles of their thorax to temperatures as high 90 to 95^o F.   Heinrich discovered that “maintenance of high thoracic temperatures at low air temperatures depends on (1) the ability to begin shivering at very low muscle temperatures, (2) a thick insulating pile, and (3) counter-current heat exchangers that retard heat flow to the head and to the abdomen, respectively.”  The heat exchangers allow heat to be concentrated in the thorax where it is most needed to promote rapid beating of wings for flight in cold temperatures. 

Flight enables the moths to obtain energy-rich nectar from witch-hazel flowers or from sap issuing from tree wounds.  Food, in turn, serves as fuel for heat generation and other metabolic activity essential for winter survival.  Because food and the opportunities to obtain it are scarce in winter, both food and heat must be conserved.  Conservation of food is accomplished by conserving heat, and body heat is retained by a thick, insulating pile around the moth’s thorax where heat is most needed.  In addition, in addition to the harmonious interaction of these three interdependent bodily systems, the life cycle of noctuid moths is turned around.  The moth larvae hatch and aestivate throughout summer and then the adults emerge to be winter-active.

How such an interdependence of the noctuid moths and the witch-hazel has come to exist is difficult to explain by accumulation of chance mutations and natural selection.  Absence or malfunction of any one physiological or morphological trait or sequence of interdependent parts would jeopardize the whole.  It is one thing to describe complex, interacting systems within an animal and within a plant and how they interact in synchrony between each other. But it is quite another thing to explain how these interactions occur.  Add to this the challenge of explaining how these interacting systems could have come into existence in the first place and you have an even greater challenge for science. 

Perhaps our wonder at the complexity of the interaction of witch-hazels and winter moths ought to bring us back to the approach of George Bartholomew and Bernd Heinrich.  Become a careful observer of the plant or animal under investigation and let it “tell [you] what questions to ask.”  It turns out that Job, an ancient man of faith in God, had already adopted this approach and it caused him to gratefully worship his Creator God (Job 12: 7-10):

“But now ask the beasts, and let them teach you;
      And the birds of the heavens, and let them tell you.
“Or speak to the earth, and let it teach you;
      And let the fish of the sea declare to you.

And what should we to learn from observing the amazing world?  Shouldn’t we also ask the beasts and let them tell us, or ask the earth and let it teach us?   And then, we may come away in awe as Job did as he humbly concluded:

“Who among all these does not know
      That the hand of the LORD has done this,
In whose hand is the life of every living thing,
      And the breath of all mankind?

For ever since the world was created, people have seen the earth and sky. Through everything God made, they can clearly see his invisible qualities—his eternal power and divine nature.  So they have no excuse for not knowing God. – Romans 1: 20 NLT