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NatureSpeak Articles

Why George W. Bush loves horsetails

It may be hard to picture a hard-bitten Texan loving anything that doesn’t moo, but it’s true. President Bush loves horsetails.

Why? Because from about 360 to 286 million years ago, the tropical climate of much of the northern hemisphere allowed strange plants like giant horsetails and tree ferns to flourish. During that time, 15 metre-tall horsetails and mangrove-like swamps covered much of what is now the great white north.

The horsetail’s time in the tropical sun was relatively brief (only 74 million years), but it was long enough for a whole bunch of them to die, fall to the ground, and decompose. As sediments formed over top of the decaying plants, they were pressured from peat into coal and, voila, a fossil fuel was born. (And has George W. ever met a fossil fuel he didn’t love?)

The history of seedless plants like horsetails and ferns is a glimpse into evolution. They reproduce by spores – an adaptation which served very well until a flashier way to reproduce came along. The evolution of seed plants (which include all our local trees, shrubs, and flowers) pushed horsetails and ferns aside. The first seed plants included conifers, and they reigned supreme until about 100 million years ago. It was only then that the reproductive advantages of the newly-evolved flowering plants took the stage.

World-wide today, there are about 15 relatively diminutive species of horsetails (scientific name Equisetum, from equus for horse and seta for bristle). Our two local representatives are common horsetail and scouring-rush, both of which have stems jointed like bamboo. The hollow stems are ribbed between the nodes, and the ribs are strengthened with silicon dioxide (a.k.a. sand).

Common horsetail has two distinct forms: sterile shoots branched like shaggy green bottle brushes, and unbranched, fertile shoots which look like brown asparagus spears. The purpose of the sterile shoots is to photosynthesize enough energy to power the non-photosynthetic fertile shoots, which then produce spores.

Scouring-rush looks more like a big green straw than a plant. There are no branches and it has only one form; photosynthesis and spore production occur on the same stem. Scouring-rush’s claim to fame is hinted at by the name. First Nations people and early Europeans used its sand-impregnated cells like steel wool to polish wooden tools and other objects.

That’s a long way around to introducing horsetails. But maybe once more people know more of their noble lineage their stock will rise as much as shares in a coal company.

Written by: Bob Brett


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