Preparing Your Winter Garden: Straw Mulch vs Cover Crop

By Pritha Golden, Portland Edible Gardens

Autumn in the Pacific Northwest is the time of year to start preparing gardens for the cold wet winter months. After removing summer crops it is usually too late to plant more veggies, so what do you do with all that exposed soil? Ecological growers always say not to leave soil bare. But why is this, and what should you do in your garden?

Why not leave bare soil for the winter? The cornerstone of happy plants in an organic system is healthy soil. As such, we take great care to tend to the health of our soil and its biology. Macro and microorganisms are critical contributors to healthy soil and one of the things they need to thrive is air. When soil is left bare for the winter it compacts with the rain and loses important air pockets. 

On the other hand, the presence of roots or mulch prevents soil compaction, preserving needed air pockets and healthy biological life through the winter. If you are someone who likes to see the evidence for themselves, mulch or cover crop one half of a garden bed, leave the other half bare and compare the results come spring. You will see for yourself that the difference is night and day.

Cover crop (sometimes referred to as a living mulch or ‘green manure’) is a plant grown to improve soil health. If a cover crop is planted in the fall, the roots prevent soil compaction during the winter. When these plants are chopped and integrated into the soil before they get brown and woody, they feed microbes and deposit important nutrients into garden soil. Some cover crops even capture precious nitrogen from the atmosphere and transfer it into the soil, a process is known as fixing nitrogen.

Dry mulch is a layer of dry plant material that is added to the top of soil to protect it. During the winter months dry mulch reduces soil compaction and increases soil temperature leaving a more habitable environment for a thriving living soil.

Why choose dry mulch for small spaces? Depending on the goals you have for your garden, you may find that mulch, cover crop or some combination of the two are the best match for you. Because we aim to get the highest production possible out of small spaces, we often start planting our gardens at the beginning of March or even the end of February. The benefit of a dry mulch is that when you are ready, you can simply remove it and start preparing the soil for planting. 

Cover crops need to be chopped and integrated into the soil (which can be quite labor intensive) and break down completely before planting. This process takes anywhere from a couple of weeks to a couple of months and can significantly delay the beginning of the garden season. In short, dry mulch has many of the advantages that come with planting a cover crop without the wait time.

We love using straw because it is easy to source and apply. As well, its criss-cross structure allows for garlic leaves to easily pop through as it grows. Remember, if you choose to mulch your garden with straw it is not interchangeable with hay. Hay has many more seeds, and can create much more work when removing in the spring

Hopefully this helps you decide what care is right for your winter garden. To healthy soil and happy plants!

Preparing Your Winter Garden: Straw Mulch vs Cover Crop

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