In the middle of Winter, in our temperate climate, you might not think there’s much nature to be seen. But, right now, with leaves off the deciduous trees, it’s the best time of the year to spot a freaky plant parasite of trees. Plants grow so slowly, that you might think they’re not very lively, or even boring. Look closer, though, and be patient, and you might see that plants are perfectly capable of as much drama and violence as animals are, if given enough time. From competition to chemical warfare, plants are actually fairly exciting, and this post is all about the most famous plant parasite of all.
Mistletoe is the common name of a family of related plants, the Santalaceae, nearly all of which are parasites of other plants, mostly trees. During the Summer, when their host trees are covered in leaves, you might not even know they’re there, but in Winter, the mistletoe growing on the tree is exposed, evergreen, when the rest of the tree is left bare. From a distance, mistletoe growing in a tree looks like this:
It’s a little green bush, perched in the branches of a tree. How does it happen? Well, here in Kentucky, we mostly have Phoradendron leucarpum, which makes white berries.Although the berries are poisonous to mammals, birds love them, and eat them, pooping out the seeds on the branches of trees, and then the seeds germinate. The seeds sprout, but instead of making roots like other plants, they make a structure called a haustorium which penetrates and connects with the host plants’ vascular system through the bark, delivering nutritious sap to the mistletoe. These little green vampires continue to suck the sap of their hosts while also growing green leaves and stems, in the form of a bushy growth. Our mistletoe is capable of making its own sugars with sunlight energy, just like regular plants, to some extent, but it can’t make roots and instead literally taps into the host to get what it needs. A few mistletoe bushes won’t hurt a healthy tree, but one that’s already sick could be killed by a very heavy infestation. Mistletoe bushes are just like plant leeches, if, instead of biting, a leech actually grafted itself to you, interconnecting your arteries with itself. I also just found out that some South African mistletoes – like Viscum minimum – don’t even go as far as to make a little bush. They don’t photosynthesize to any noticeable extent, living almost entirely inside their Euphorba succulent host, bursting out only to flower and set fruit. Look at those tiny Viscum minimum plant growths, barely noticeable on the surface of a succulent, like plant acne. Plantcne? So cute, yet so creepy. Here’s the flowers: Like Alien chestbursters, but permanently attached. And cute.
Have a safari in your own neighborhood this Winter. Look for mistletoe bushes. Notice birds – we’ve got different birds staying here in Winter, compared to Summer. Listen for Great Horned Owls staking out a territory. Even in Winter, nature never sleeps, and there’s wonders all around you, if you just keep aware of them. Including the weird tree-leeches known as mistletoe.