Thread by @brookejarvis

I noticed this gorgeous tulip, unlike any of the tulips around it, in my neighbors’ yard. I figured it was a mutation, but instead I learned something rather beautiful about a very timely subject: Viruses!

We tend to focus of the viruses that affect us. Reasonable! But they are a tiny, tiny % of them. One estimate is that the world is home to 10000000000000000000000000000000 —“as in over 10 million times more viruses than there are stars in the universe.” nationalgeographic.com/science/phenom…

Plants catch viruses, too. In fact, scientists first discovered that viruses existed by studying sick tobacco plants, which they realized were infecting each other. (Early forms of vaccines had already been used at that point, but no one knew what they were really fighting).

One unknown plant virus had a well-known effect. Some tulip bulbs were known to became “broken”—they stopped coming up the same color, and instead showed beautiful streaked, feathered, or striped patterns. apsjournals.apsnet.org/doi/pdf/10.109…

The most sought-after tulips sold during the 17th century tulip mania, and the ones that drove prices sky-high, were those with white or yellow streaks on colorful backgrounds. The most expensive of all was the Semper Augustus, which looked like this:
(en.wikipedia.org/wiki/File:Semp…)

Breeders, who didn’t know what made tulips break, tried to make it happen by changing manure and soil depth and how they stored their bulbs. That’s part of why tulips got so expensive: People were speculating on bulbs that might or might not produce the tulips they wanted.

It wasn’t until the 1920s/30s that “tulip breaking virus” was discovered. Spread by aphids, it eventually weakens tulips, generation after generation, until the bulbs can no longer flower.

Semper Augustus and most of its fellows are long gone. A few “broken” tulips for which the virus is mild—we don’t know why—have managed to survive for centuries. “Zomerschoon” (l) was registered in 1620 and was popular during tulip mania. “Absalon” (r) was registered in 1780.

Other kinds of commercial tulips that appear broken have achieved that look through breeding, not the virus. To protect their tulip industries, many countries have banned the sale of broken bulbs, the ones that were once the most prized but whose beauty came at too high a cost.