“And what is a weed? A plant whose virtues have not yet been discovered…” –Ralph Waldo Emerson, from Fortune of the Republic
All hail the tumbleweed, denizen of deserted steppe, itinerant ditherer of the dusty plains. It goes wherever the wind and the land dictate, often shedding seeds as it bumbles. Around boulder and over hillock it canters, cantankerously, seeming to ask as it rolls by: “Why do you notice me?” It speaks – whether we listen or understand – of life past and passing on; of wide open spaces and perhaps loneliness; of a spirit at once opportunistic and inscrutable.
So, what exactly is a “tumbleweed?” Usually the term describes a type of bushy plant whose entire above-ground mass forms a rounded shape and breaks off. Then it’s off to the races as the wind carries the plant, whose seeds are shaken loose, little by little, across the plains. Several types of plants perform this trick, but perhaps the most iconic are those of the Salsola family, usually called Russian sage. Large plants can produce 100,000 tiny seeds and have thorns sharp enough to pop bike tires or pierce threadbare soles.
Though native to Eurasia, Europeans introduced Russian sage (Salsola pestifera) to North America in the late 19th century. It then spread throughout the West and South and is considered a nuisance by farmers. Like many invasive plants, it does better in disturbed habitats like roadsides and areas with loosened topsoil.
This is where the “weed” comes in: most tumbleweed species grow quickly and outcompete other types of plants. In one study, for example, Russian sage sucked up an average of 44 gallons of water when competing with wheat, which can be the difference between a good wheat harvest and a bad one.
However, this thirstiness and ability to remove chemicals from the ground could be useful. For example, another species of Russian sage, Salsola kali, accumulates high levels of various toxic pollutants, which might allow it to help clean up contaminated sites. S. kali accumulates high levels of the heavy metal cadmium, which is extremely toxic to animals and plants even in minute quantities. The plant can also help rid soil of technetium, a radioactive byproduct of nuclear fission.
Many other plants can also form tumbleweeds, such as the plains tumbleweed, or Cycloloma atriplicifolium. Native to central North America, its seeds were consumed by Native Americans.
If you see a tumbleweed in your travels to the Middle East or North Africa, it’s likely a Rose of Jericho. Also known as “wheels,” the plants could have probably taught the ancient Egyptians a thing or two. These hardy herbs shrivel up into a ball in the dry season and take to the wind, a strategy thought to help avoid burial by sand dunes. Seeds stay dormant but vital for many years. When the wheel finds a moist spot, the knot opens and seeds can germinate within 18 hours or less.
Certain types of fungi called puffballs, or Bovista, also pursue the tumbleweed strategy; they form fruit bodies up to three inches in diameter which can disconnect from the ground and disperse in the wind, spreading spores. Bovista fruit and spores have been used in homeopathy to treat ailments such as discomfort from tight clothing, an itchy coccyx or inclination to “drop things from powerless hands.”