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Indian pipes

Walking through our woods back in mid-July, we came across several clusters of Indian Pipes. These delicate looking plants have a waxy texture and are generally pure white. They are quite striking against the brown background of leaf litter on the forest floor. Looking at them, you would swear they were a type of fungus. There is not a trace of green on them anywhere. The ones in our woods were pure white or white with black flecks. Sometimes they can be found with a blush of pink or even a red tint to the stem and flower.

Delicate pure white flowers

Delicate pure white flowers

Yes, I did say flower! Indian pipe (Monotropa uniflora), sometimes called the Ghost Plant, is a flowering plant, an angiosperm, not a fungus. The lack of chlorophyll (the green pigment found in most plants) does not necessarily classify something as a fungus. Believe it or not, Indian pipes are in the same family of plants as blueberries, azaleas, and rhododendrons – the Ericaceae.

These wildflowers have very delicate flowers with translucent, waxy petals and sepals. They are pollinated by small bees and other insects and eventually produce tiny seeds. On the stem are small scale-like leaves that, like the stem, contain no chlorophyll. Each stem bears a single flower; hence the species name uniflora, “one flower”. As the flower matures and the seeds develop, the flower begins to turn upward and eventually points straight upward, becoming aligned with the stem.

The roots of squawroot pull nutrients directly from the roots of their host tree.

The roots of squawroot pull nutrients
directly from the roots of their host tree.
Photo by Eric Jones

An interesting relationship

Green plants are autotrophic (self-feeding) and produce their own food through photosynthesis. Indian pipes and other plants that lack chlorophyll, like squawroot, broomrape, and pinesap, are heterotrophic (other-feeding). Since they have no chlorophyll, they cannot make their own food and must rely on other organisms for nutrients and as such are parasitic plants.

Squawroot (Conopholis americana) and broomrape are root parasites and survive by obtaining nutrients directly from the roots of a host tree.

Indian pipe and pinesap belong to a group of heterotrophs called mycotrophic (fungus-feeding) plants. They have a very unique parasitic relationship with the mycorrhizal fungi that are associated with certain tree species. Indian pipes are commonly associated with beech trees and indirectly receive nutrients from these trees. Here’s how it works:

A cluster of Indian pipe flowers

Indian pipes obtain nutrients from the host tree indirectly by way of mycorrhizal fungi.

Mycorrhizal fungi are a type of fungi that form a symbiotic (mutually beneficial) relationship with trees and many other plants. In this association, tremendous numbers of mycorrhizal filaments (hyphae) attach to and enter the roots of the tree and then fan out into the surrounding soil. The mycorrhizal filaments capture minerals and water which are then transferred to the tree. These “extensions” of its root system exponentially increase the area that the tree can exploit for the raw materials needed for growth and also increase the tree’s tolerance to drought stress. In return, the fungi feed on carbohydrates and other nutrients that are produced by the tree. Each member in the relationship helps the other.

Indian pipesThen along come the mycotrophs like the Indian pipes! Their roots tap into the mycorrhizal hyphae and “steal” nutrients from the fungi; nutrients that the fungi absorbed from the tree roots. These plants give nothing back to the fungi in return for the food they take nor do they provide any benefit to the tree that produced the nutrients to begin with. Such parasites these wildflowers are!

What an interesting and complex system!

Isn’t nature fascinating?

Oh – and by the way, not all fungi are white! But that’s another story …

Until next time – Happy Gardening!

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