Saturday, February 21, 2015

An everyday epiphyte

Mistletoe, Phoradendron spp.
Great Purple Hairstreak
Remember this guy (at left)? Remember how his caterpillars only eat mistletoe? For this and other reasons, our Texas mistletoe (Phoradendron spp.) is worth another look.  Mistletoe is an arboreal hemiparasite, related to sandalwood (another hemiparasite), with fleshy green leaves and stalks. It grows best as a rounded clump in the upper branches of hardwood trees where it has access to abundant sunlight and can practice its nutritional thievery unmolested.

Besides the caterpillars of the lovely great purple hairstreak and some other Lepidoptera, few creatures eat the toxic leaves of this plant. Birds, however, adore its fruit.  The berries are a valuable winter food source. Providing winter nourishment is not an act of philanthropy on the part of the mistletoe. Mistletoe berries are extremely sticky. Birds eat and poop them out, wiping off their little tails, feet, and beaks on the branches of a preferred roost, effectively dispersing the mistletoe progeny. It's ingenious. Humans appreciate and disperse mistletoe berries for their own purposes. Specifically-- stolen kisses in the holiday season.
A few white berries

Despite its bad reputation, mistletoe is unlikely to bring down a tree single-handedly. It may sap the vigor and weigh down individual branches, but it is unlikely to seriously harm an otherwise healthy tree. This is good news, because once established mistletoe is nigh impossible to remove. Cutting off a branch to excise the plant causes more harm to the host tree than leaving it in place. This practice is unlikely to completely remove the mistletoe anyway.

By flowering and fruiting in the winter, mistletoe provides resources when little else is available. It is well past time for blooming, but I saw some mistletoe flowering today anyway. The inconspicuous yellow flowers are a pollen source during this season of scarcity. Male and female flowers occur on different plants, and reproductive development is slow. Mistletoe doesn't typically flower before its third year. The large clusters you see in treetops are decades old.

I like epiphytes and parasitic plants.  I don't really have a good reason-- I guess they have a "tropical" feel. I can understand a homeowner not being thrilled at the arrival of this clever little plant on a favored shade tree, but seeing as there's no stopping it, you may as well take a philosophical perspective.  You can decide to appreciate its genius, and be comforted that it is unlikely to do serious harm for a few more decades.
Male flowers?


  1. Back when your granddad was a boy, he collected mistletoe for the holidays by shooting it out of trees with his .22. :)

  2. Glad to see your getting your use out of the hairstreak photo.