Get smart curated videos delivered to your inbox every week.      
The Kid Should See This

Why Do Tumbleweeds Tumble?

When we think of a desolate plain or a foreboding frontier town in the wild west, we might think of the iconic tumbleweed rolling through the scene. Or they might roll through as a joke. But for people who live in dry parts of western North America, the tumbleweed is, in fact, a weed that can block doors or clog waterways as they gather in piles. They’re neighborhood nuisances that create fire hazards. They also cause accidents when they roll out onto roadways.

As it turns out, tumbleweeds are not native to the United States. They’re invasive Russian thistles that flower, die, dry up into a spiny skeletal ball, and roll. Why? Seed dispersal. From KQED via PBS NewsHour:

Tumbleweeds start out as any plant, attached to the soil. Seedlings, which look like blades of grass with a bright pink stem, sprout at the end of the winter.

By summer, Russian thistle plants take on their round shape and grow white, yellow or pink flowers between thorny leaves. Inside each flower, a fruit with a single seed develops.

Starting in late fall, they dry out and die, their seeds nestled between prickly dried leaves. Gusts of wind easily break dead tumbleweeds from their roots. A microscopic layer of cells at the base of the plant — called the abscission layer — makes a clean break possible and the plants roll away, spreading their seeds. When the rains come, an embryo coiled up inside each seed sprouts.

Learn more from the Deep Look video above: Why do tumbleweeds tumble?

Then explore the tumbleweed’s classic image in American pop culture with this tumbleweed supercut by Duncan Robson, a short video commissioned by the Columbus Museum of Art:

Next: Why the Giant Sequoia Needs Fire to Grow, exploding plants disperse their seeds with high pressure bursts, and TED Ed’s Symbiosis and a surprising tale of species cooperation.

🌈 Related videos

Seeds, plants, & flowers twist, wiggle, & extend: Micro time lapse

Rion Nakaya

Why the Giant Sequoia Needs Fire to Grow

Rion Nakaya

Time lapse radish seeds sprouting

Rion Nakaya

Pygmy Seahorses: Masters of vibrantly-colored coral camouflage

Rion Nakaya

The Amazing Life of Sand – Deep Look

Rion Nakaya

Desert Fox Hunts A Lesser Jerboa – BBC’s Wild Arabia

Rion Nakaya

The Fungarium and Millennium Seed Bank Partnership at Kew

Rion Nakaya

Entropy: How a sandcastle reveals the end of all things

Rion Nakaya

How Do Reindeer and Elk Get Their Astounding Antlers?

Rion Nakaya

Get 7 smart videos delivered every week.