I was preparing a bed for planting last fall and while I was turning over the soil, I kept pulling up jet black roots about 1/4 inch in diameter. They had sinewy, white centers and traveled all over the 15 by 30 foot area I was working. What are these roots? I remember some ferns popping up in this area earlier in the year.
I suspect you may be encountering the bracken fern, common throughout Michigan and the Great Lakes region. It reproduces by spores produced on the underside of the leaves and spreads by way of a thick, black and scaly rootstock that may grow to a length of 20 feet or more. Shoots can pop up almost anywhere along this rootstock. A vigorous root system, such as the one produced by this fern, can be quite invasive and can quickly spread out of control making a pest of itself. However, the roots will not survive if they are not nourished by the top growth. Continue to pull out the roots as you work the bed. Eliminate any top growth as it appears and the root system will eventually die off. Be persistent in your efforts and you will gain the upper hand.