Ask a local master gardener about cover crops

  • Stacked bales of pine straw in spring, horizontal aspect Getty Images/iStockphoto

  • Getty Images/iStockphoto

For the Gazette
Published: 10/26/2018 2:49:28 PM

Q: Eeek! I waited too long to plant a cover crop in my vegetable garden. What can I use now to protect the soil over winter? —A.T. Northampton


A:  Take comfort in knowing you are not alone in this dilemma, A.T.! You are correct in knowing it is important to put some sort of winter protection over any bare soil after clearing out your vegetable garden at the end of the season. 

Unlike springtime mulching, which is done to suppress weeds, feed the soil and help retain moisture, the purpose of mulching over winter is to protect the soil from our New England freezes, thaws and bitter winds.  Three examples of good winter mulches to use are clean straw, shredded leaves, and pine needles. Put them loosely over any bare spots, about 2 – 4 inches deep. 

Straw typically needs to be moved in the springtime. If you grow garlic over the winter, straw is a great insulator for it, and the garlic will simply grow up through the straw in the spring. If you use a thin layer of pine needles or shredded leaves, they will not need to be moved in spring. 

Ensure leaves are indeed shredded so they do not mat or clump together — preventing rain or melting snow from seeping through them into the ground. Clean grass clippings can be added to provide extra nitrogen and aid leaf decomposition. 

Pine needles and shredded leaves tend to be acidic, so it is good to have your garden soil pH tested in the spring to confirm it is where you want it to be. Testing your garden soil pH is, in fact, always a good practice in the springtime.

A quick lesson here on the difference between hay, straw, and salt marsh hay is in order: Hay is an assortment of forage grasses and contains weed seeds. Because of these seeds, it is not a good mulch choice. Straw is the stems of field crops like wheat and oats. It is a good mulch option because it does not contain seeds, is readily available and is hollow, thereby holding air and acting as a bit of insulation. Here in Western MA one sometimes sees salt marsh hay for sale as a mulch, too. It is a fine option. Unlike traditional hay, salt marsh hay is harvested from salt marshes and the seeds will not germinate here as they require salty, marsh soils which we do not have. 

Good luck with your mulching, A.T. and thank you for asking a Master Gardener!

Have a gardening dilemma? Please send your questions, along with your name/initials and community, to the Western Massachusetts Master Gardener Association at One question will be selected and answered per week.

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