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Your Garden in Winter

The underground story

Did you know that your bare garden soil is losing its nutrients to winter?
    That’s just what’s happening in your vegetable garden unless you planted a cover crop last fall. And in your flower garden, unless it’s planted with perennials or woody plants.
    Here’s the underground story.
    During the growing season, plants do not utilize all soil nutrients, whether applied as fertilizers or released from animal manures or compost. Nutrients such as nitrogen, potassium, magnesium and boron, to name a few, are quite soluble. Unless they are absorbed by roots of plants, they leach downwards into the water table, into streams and eventually into the Bay.
    A good garden soil is biologically active all year long except when soil temperatures drop below 34 degrees. At that temperature microbial activity stops, nutrients are not as soluble and most things stay in place. However, as you penetrate deeper in the soil, temperature rise and nutrients that have penetrated to that depth continue to leach downwards. Thus you want all soluble nutrients to be absorbed by roots before they seep too deep where roots do not penetrate.
    The physical movement of soil particles during periods of freezing and thawing causes soil particles to move about, creating crevices, thus facilitating the downward movement of soil particles as well as nutrients in solution. Established roots help to stabilize soil and prevent particles from either blowing away in drought or washing away through erosion. Both cover crops and perennials absorb available nutrients. When the cover crop is plowed or rototilled under in the spring, its roots, stems and leaves will decompose, and those nutrients, like compost, will be slowly released in the soil.
    While soil temperatures are above freezing, roots are absorbing nutrients. Roots of some species are capable of growing in soil temperatures as low as 36 degrees. Roots can grow all winter as long as the soil does not freeze. Unlike the top of plants, which stop growing when they begin to go dormant in late August and early September, roots continue to grow and absorb nutrients and water.
    I tested this concept in the mid 1970s by transplanting young dogwoods between the greenhouses at the University of Maryland in College Park. Half of the dogwoods were transplanted above a buried steam pipe. Snow there never lasted more than a few days, while between adjoining greenhouse the snow stayed in place. In the spring, I dug up the dogwoods in each area. The root system of the trees where the snow melted rapidly were two to tree times bigger and more fibrous than the roots of the dogwood trees from where the snow remained and were then five to six times larger.
    Never allow land to remain fallow without vegetation. Keeping the soil covered with growing plants not only protects the Bay but also maintains biologically productive soil for you to grow crops. Nutrients belong in the soil and not in the Bay.


Ask Dr. Gouin your questions at DR.FRGouin@gmail.com. Please include your name and address.