Here are some sobering statistics as you begin the weeding season on your farm or market garden: A Minnesota study found that a square foot of soil, 6 inches deep, contained from 98 to 3,068 viable weed seeds. Many seeds remain viable for decades; Jimsonweed has a 90 percent germination rate after 40 years in the soil and field bindweed seeds are viable for more than 50 years. All those seeds are just sitting there, in what is known as the “weed seed bank,” waiting for favorable conditions that will allow them to germinate.