And then there were five.

When William James Beal crept out under cover of night and buried 20 uniform bottles filled with a mixture of soil and seed in 1879, he lit the fuse on agriculture’s longest running experiment. Each bottle was scheduled to be dug up at a set year in the future, farming’s version of a time capsule chain. Beal passed in 1924 and as 2016 rolls by, five of his bottles remain hidden.

By tilting 20 narrow-necked bottles downward to ensure moisture-wicking, and covering them with several inches of dirt on the campus of Michigan State University (MSU) in Lansing, he was attempting to answer an age-old question: How long do weed seeds remain viable in soil? Beal’s quest, started 137 years back, is still packed with relevancy for modern agriculture.

He placed 50 seeds from 23 weed species into every 3” by 7” bottle. Beal was operating in an age where much of the weed world was a black box. Horse-drawn mechanics, hand labor, and a lack of herbicide drove Beal to question why the seed bank never ran dry. By burying the bottles, he was ensuring a means to retrieve a known quantity of seed of a known species. Below ground, devoid of sunlight, the seeds wouldn’t germinate.

As curator at WJ Beal Botanical Garden, Frank Telewski is heir to the bottle experiment. As a graduate student learning about the hidden bottles in 1980, Telewski never imagined the mantle would pass to him as an MSU plant biologist. Telewski dug up the 15th bottle in 2000 and will uncover another in 2020. “I won the lottery. I’m so honored to carry on this work,” he says. “It’s a tremendous responsibility to make sure it’s passed on correctly.”

Beal’s bottles are recovered at night to avoid sunlight and the public eye. The contents are removed and carefully spread thinly in sterile soil to avoid contamination. The mix is watered before Telewski watches and waits. Mullein has proven the most robust weed seed in the trial, germinating after every bottle retrieval. Mullein seeds are tiny and store a miniscule amount of energy, yet are able to retain respiration and stay alive for over 120 years. The experiment has repeatedly demonstrated the ability of common weed seed to remain viable over long periods, lurking in the soil and waiting for a touch of sunlight. “Beal has shown that tilling constantly exposes old seeds to sunlight. He’s also letting us check the changes in genetics of old plants against our plants today,” Telewski says. “Are they more robust? There are valuable questions addressed by Beal’s forward-thinking research.”

“Professor Beal's buried seed experiment provides us with the best and most accurate documentation of the longevity of seeds, especially weed seeds, buried in the soil,” says Carol Baskin, professor at the Department of Plant and Soil Sciences, University of Kentucky. “Over the years, testing has shown how many seeds of each species were still alive and capable of germinating. Other such studies have been attempted, but for various reasons they were terminated within a relatively few years.”

Initially, Beal scheduled a bottle extraction every five years: 20 bottles equaled a century in duration. In 1940, after finding stabilization of germination rates, MSU changed the extraction schedule to a 10-year interval. The interval currently stands at 20 years and the final bottle will be removed in 2100.

Beal is an agricultural giant, remembered as the father of hybrid corn. His work on hybrid vigor helped push corn from 8 rows to 24 rows of kernels. In 2020, Telewski will approach Beal’s hidden cache in the dark of night for the last time. Flashlight and spade in hand, he’ll dig up another piece of Beal’s legacy and fill in more puzzle pieces surrounding the mysteries of the seed bank.

“I’ll be 65 at the next extraction and rest assured, this will go on well past myself,” Telewski says. “When you see the glint of a glass bottle filled with seeds and sand buried in 1879, the feeling is exhilarating. It’s truly digging into agricultural history.”