On Gardening: In praise of a $5 butterfly and its mistletoe

April 27, 2015
The great purple hairstreak is one of our most beautiful butterflies and unbelievably requires mistletoe to exist.

I remember it like yesterday. I returned from a Rotary Club meeting in Mission, Tex., to see a good sized group with cameras gathered around a patch of flowers at the National Butterfly Center there. I quickly went in and asked what were they seeing? The answer was a Great Purple Hairstreak butterfly. Today when I give a presentation on butterflies I typically call that one a $5 butterfly, in other words it is so showy itís worth the price of admission.

Despite the fact that this large hairstreak sporting iridescent colors may be found along the east coast from Florida to Maryland, west to Missouri, Oklahoma and Texas, continuing to New Mexico, Arizona and up the west coast to Oregon it seems the gardening public hasnít paid attention. It is indeed a rare group of gardeners I speak to that includes even one who has ever seen the Great Purple Hairstreak butterfly.

While we teach and labor toward restoring milkweed for Monarchs, which is their only larval food source, the Great Purple Hairstreak is also on a rigid diet. The caterpillar will feed only on mistletoes. Yes, even the mistletoe has a purpose in life. Actually, there are a couple of other hairstreak species that also feed on mistletoes.

Believe it or not there are 30 mistletoes native to the United States, and, as you may remember, they are indeed parasites. There are people who make money selling mistletoe. Iíve seen it for sale in craft stores. But if you want to read about mistletoe, go to the book called "Diseases of Trees and Shrubs." Several pages are dedicated to this affliction of our beloved trees. Yet remember they serve a purpose.

Itís not just some of our most colorful butterflies or pollinators that must have them, but some of our favorite birds thrive in forest because mistletoe is present. Roger di Silvestro, writing for the National Wildlife Federation, states that a mistletoe-infested forest may support three times as many cavity nesting birds as a forest without. You see, it is the trees dying off that provide these strategic nesting sites.

While I was shooting photos of a native passionflower vine growing in our shaded forest in coastal George a pileated woodpecker flew, in enticing me to quickly change my subject matter. These giant woodpeckers that can reach 18 inches-in length are an example of cavity nesting birds. Their familiar thumping or drumming can be heard throughout the canopy of trees making the forest come alive with excitement. The same came can be said for the red-headed woodpecker that never fails to bring out the cameras. For this we may indeed owe a debt of gratitude to the mistletoe.

The eastern mistletoe parasitizes about 110 host species in 50 genera. Host groups include ash, beech, birch, hickory, maple, oak, pecan, sycamore, walnut and willow. The mistletoe, through a device called a sinker, becomes deeply embedded in the tree trunks. After several years they are considerably below the site of the original infection. So to remove, the branch must be cut below the mistletoe sight.

Birds spread mistletoe from tree to tree when they eat the pulp around the seeds, which stick to them. The seeds then germinate and the parasite grows through the bark into the treeís water-conducting tissues where the sinkers develop. The white fruits and seeds are poisonous to humans but relished by a host of birds and mammals.

Over the years I have had a good laugh at the expense of Oklahoma for naming the mistletoe as their State Floral Emblem. Now as I have matured in my thinking and become more passionate about nature I would like to tip my hat to the Sooner State. You were ahead of your time way back in 1893; Iím guessing you already knew mistletoe serves a valuable purpose.