Works in Progress - Spring 2009

Locks for Lettuces

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By Sam Kean

October 9, 2013


 

The grisly belief that a person’s hair continues to grow after death is an urban legend, but studies at Mississippi State University are proving that hair clippings still have a little life in them.

In a series of experiments, plant and food scientists added three to 10 ounces of human hair to potted plants. Hair breaks down in soil like any organic matter and releases all dozen or so of the nutrients plants need, especially nitrogen. Nitrogen is often the limiting factor in plant growth—Venus flytraps and pitcher plants swallow flies for their nitrogen—so finding a cheap alternative source would be a boon.

The Mississippi team tested feverfew, lettuce, wormwood, and yellow poppies to give them a range of plant species. Over the short term the plants did better with

hair than without hair, though not as well as plants with commercial fertilizer. That’s because hair takes weeks to break down, whereas roots can absorb fertilizer instantly. So while hair cannot replace fertilizer for fast-growing plants, it could be an ideal supplement for established plants since it works steadily for two or three years.

The hair tested as fertilizer was imported from India and China because, scientists said, people there expose their hair to fewer chemical hygiene products. Because hair itself is indigestible (that’s not an urban legend) and absorbs pollutants like heavy metals, it remains to be seen if hair is a suitable supplement for food, or whether clippings, beard shavings, and other trimmings are best for bushes, flowers, and decorative vegetation.

Sam Kean is the author of two books on science history, The Disappearing Spoon and The Violinist’s Thumb.


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