Horsetails rooted in history

Long before scouring pads were invented for cleaning dishes, Europeans and American settlers utilized what was available in nature--scouring rushes and horsetails. The widespread use of scouring rushes for cleaning wood and pewter utensils gave scouring rushes their name. 

The branches of horsetails grow in whorls around a single stem

Not only good for cleaning, Native Americans used horsetails like sandpaper. Equisetum species, including scouring rushes and horsetails, contain silica in their cell walls which makes them rough to the touch and good for cleaning and sanding. 

Horsetails and scouring rushes are unique plants found almost worldwide except for Australia, New Zealand and various islands. The common horsetail is one of the most widespread plants in the world, even found in the Arctic. 

Also called marestail, horse pipes, jointed monkey grass and snake grass, horsetails can be identified by their jointed, hollow stems with small branches borne in whorls. The difference between scouring rushes and horsetails is that horsetails have branches and scouring rushes have only a main stem.

One unique aspect of horsetails and scouring rushes is that the leaves aren’t visible from afar. Upon close inspection, one can see the leaves as small teeth or scales united by a sheath. Without significant-sized leaves, the majority of photosynthesis occurs in the stems. 

Horsetail leaves have been reduced to teeth united by a sheath at the nodes

Also barely visible is the second stage of the horsetail’s life cycle. The visible plant is the spore producing stage (known as the sporophyte). The second stage, the gametophyte, is a small multi-cellular structure that produces the egg and sperm. The egg and sperm fuse and produce the sporophyte. This two-stage life cycle is known as ‘alteration of generations’ and is also found in ferns and club mosses.

Spore germination requires precise ecological conditions and isn’t the main reproductive method for Equisetum species. Instead, vegetative reproduction through rhizomes is the main method.

Scouring rushes and horsetails have extensive rhizome systems underground--up to six feet deep and up to hundreds of square feet in area. The deep rhizomes access groundwater and help the plants survive disturbances such as plowing, fire, drought and burial. Horsetails are commonly found in wet areas but the deep rhizomes allow them to grow in areas that appear dry at the surface.

The quick growth of rhizomes enable horsetails to colonize disturbed areas. After Mount St. Helens erupted in 1980, horsetails grew through the volcanic tephra (ash and silt) to form thickets. 

Reproduction by rhizomes creates dense thickets of horsetails in wet areas

Since each new stem grown from the rhizome is a clone, the plant is considered to have a limitless life span. 

Equisetum species are also considered a living fossil. Horsetails and scouring rushes are living representatives of a group of plants that flourished during the Coal Age and in the Carboniferous swamp forests over 300 million years ago. 

The fossil relatives were medium-sized trees up to 65 feet high and grew in thick forests. They exhibited the same characteristics of grooved and jointed aerial stems that contained silica in the cell walls. 

The long life of Equisetum species may be attributed partially to the silica which protects the plant from fungal diseases and insect attacks. Remarkably, plants can take up silica (also known as silicon dioxide) even though silica is poorly soluble. Silicon dioxide comprises 59 percent of the Earth’s surface and is most commonly seen as quartz. 

On the molecular level in plants, silicon dioxide is absorbed and deposited in the cell walls of horsetails and scouring rushes, enabling humans throughout history to scrub their pots and pans clean.