According to the Detroit Free Press, a weed you may see growing along the road in East Lansing, Michigan this fall is part of the world’s longest continuous botanical experiment to test how long seeds can produce flowers.
The flowering plant is called moth mullein. It has dark green leaves and bears yellow or white flowers on a stalk that reaches about 3 feet tall. Moth mullein is related to common mullein. You can tell the difference because common mullein gets taller, the flowering stalk is thicker and its leaves look like gray-green felt.
Mullein isn’t native to the United States; people brought it here from Europe and Asia many years ago and it now grows across the country.
When a mullein seed starts to grow, the plant makes a long root and a low-growing set of leaves called a rosette. It stops growing in winter. The next spring and summer, it begins to grow again and produces the flower stalk.
Many plants’ seeds are in the soil and able to grow if they are exposed to light. Mullein seeds remain viable, or able to grow under the right conditions, for more than 100 years.
Just how long they can grow is being tested in an experiment at Michigan State University in East Lansing. In 1879, a botany professor named William Beal started an experiment. He wanted to see how long seeds could remain viable. So Beal gathered seeds from 21 common plants, including the moth mullein plant. He got 20 glass bottles and put some seeds, in moist sand, in each one. Then Beal buried the open bottles, upside down.
Starting in 1884, Beal dug up a bottle. He took out seeds and exposed them to light to see how many would germinate. Some grew. Another bottle was dug up every five years through 1914. It was too cold to dig up a bottle in late fall of 1919, so the next bottle was dug in 1920.
Other people have carried on Beal’s experiment. They began waiting 10 years between digs, to make the experiment last longer. Starting in 1980, they decided to wait 20 years.
The 15th bottle was dug up in the spring of 2000. It contained 1,050 seeds. Of those, 25 plants of moth mullein grew. Within a few months, those 121-year-old seeds had grown into new plants with bright flowers.