Nature Notes: Parasite Plants

The American beech secretes root pheromones that discourage other species from moving in
Dodder, left, Beechdrops, right.

It’s fall and the dogwoods, horse chestnuts, and sycamores have already turned, not so colorfully, mind you. The vast majority of trees around are still green, as are the mountain laurels, blueberries, and huckleberries under them. You won’t find any of the latter under the beech trees, however; the sheriff of Beechwood does not allow trespassers.

The American beech, like walnuts and a few other local tree species, secretes root pheromones that discourage other species from moving in. Beeches rarely produce viable beechnuts; they prefer the suckering up from maternal roots to start new offspring. There is a spot in the white oak-dominated Hither Woods of Montauk where the beeches have taken over — they prefer exclusivity to intermingling.

There are a couple of small plants that have found a way to get around Beechwood’s rules and regulations. They are beechdrops and pinesap (or Dutchman’s pipe), two parasites that tap into the stores of foodstuffs in the beech tree’s roots by way of an intermediary, fungal mycorrhizae. They are both parasites, and to a lesser degree saprophytes, but they are so sparse they are not able to harm the beeches they steal from to any significant degree. Neither species is green. Both produce flowers that can set seed if fertilized, but are devoid of chlorophyll. They are totally incapable of photosynthesizing their own foodstuffs the way normal green plants do.

One of the most spectacular nongreen plants is the perennial Indian pipe, Monotropa uniflora. It is the whitest member of the local flora, and, as the scientific name suggests, it blooms with a single flower in midsummer. The flower points to the sky while awaiting fertilization, then turns downward, toward the ground, while fruiting. As with beechdrops and pinesap, snakeroot uses a tree’s or a shrub’s mycorrhizal root attachments to pilfer its food, thus it is 100-percent heterotrophic, like the other two.

But a common green parasitic plant that we all know, because it has become a longtime symbol of Christmas in America, is mistletoe. It is common throughout much of the United States and used to grow in New York State on Staten Island, from where it was gathered and sold on the streets of New York City during the holiday season. It taps directly into the xylem and phloem layers of the deciduous trees it parasitizes and steals a share of their juices, while at the same time it carries on photosynthesis to produce sugars and starch. It is both a parasitic heterotroph and an autotroph at the same time.

Mushrooms used to be in the plant kingdom Plantae, but the latest research shows them to be closer in origin to animals than plants. Almost all are saprophytes that produce enzymes that dissolve dead material in the soil layers and incorporate it into their bodies for growth. The locally common yellow-flowered cow-wheat, Melampyrum pratense, is both saprophytic and parasitic. Saprophytes derive their nutrition by breaking down the organic matter of dead stuff with secretions, then imbibing the digested materials into their own flesh. Thus, in a way, a house fly maggot is a saprophytic animal. Similarly, many spiders are, too.

There are several other saprophytic flowering plants that grow on Long Island. Purple gerardia is one common to the entire East End. The sandplain gerardia, in the same genus, Agalinis, is listed as endangered by the federal government. It is indigenous to Montauk, where it was rediscovered in 1982 by this writer growing in what is now called Shadmoor State Park but was then up for grabs by its developer-owners.

One wonders if it, too, is a saprophyte, as Montauk used to be one of the biggest livestock-grazing areas in America early on, and the entire area east of Fort Pond was covered with its pink-purple blossoms come late August. There would have been at that time, prior to the 1900s, more than enough feces on the ground to allow it to thrive on their breakdown products. Oddly, Shadmoor in the late 1900s was one of the few places in Montauk where Rita’s horses regularly grazed and carried riders.

The largest group of truly parasitic nonphotosynthetic plants are the “dodders” in the genus Cuscuta. We have a lot of them growing locally. They are thin, wiry orange vines that travel several feet in order to find their ideal host plants. They are especially prevalent in the marsh edges of freshwater wetlands. They have special organs called “haustoria,” which tap directly into the vascular system of their host plants in order to feed. Not only that, they prefer certain plants, such as those in the tomato family, Solanaceae, see­king them out by zeroing in on the chemical odors they transpire into the atmosphere.

Remember this: Parasites would not be successful in the long run if they destroyed their hosts. Think of fleas, head lice, bedbugs, and the like. They can drive you crazy, but if they kill the host, they kill themselves. That is why the vast majority of parasites live off their hosts without killing them outright.

It’s the same with parasitic plants — they want to exist not just for decades or centuries, but for millennia. That’s why the beeches tolerate the beechdrops and the pinesaps, most trees tolerate mistletoe, and herbaceous plants tolerate dodders. Do in the host or hostess and you’re a deader; hump it a bit and you’ll survive forever.



Larry Penny can be emailed at LarryPenny9@gmail.com.

Wood Betony
Yellow pinesap
One-flowered broomrape
Indian pipe