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Help your garden soil get ready for winter

  • Fay Mark
  • “Winter is coming” is the motto of the House Stark in “Game of Thrones.” Being vigilant about feeding your garden soil before the winter rains rewards you with beautiful healthy plants and trees in the spring and summer.

    Soil is the foundation of your garden, and healthy soil is the foundation for healthy plants and trees that create food-web habitats for local wildlife, and a diverse, thriving ecosystem. No matter how much you baby your plants and trees, if the soil isn’t functional and healthy, your plants and trees will suffer.

    So how do you continue to develop your garden’s soil so you have loose, rich, fluffy soil that’s teaming with beneficial microscopic life?

    Start by understanding the structure, nutrient value and pH of your soil. Soil structure is critical for water drainage and for allowing air to reach roots. Populations of fungi and bacteria (soil saprophytes), earthworms and hard-bodied insects create micro-channels and contribute to soil nutrition. The most accurate way to determine the nutrient content, pH, structure and texture of your soil is to send a sample of your soil for analysis to a soil-testing laboratory. Contact the UC Marin Master Gardener help desk at 415-473-4204 for more information.

    While winter in Northern California is relatively mild, there are several tasks that you can perform in the fall, before the winter rains arrive, that nurture and keep your soil healthy.

    Here’s a list to help you:

    • Feed the microorganisms to keep your soil alive. Lay down up to 3 inches of organic compost and cover that with mulch. Mulch keeps weeds at bay and helps soil retain water. It cushions the soil from pounding rains, fosters root growth and allows earthworms and billions of helpful microorganisms to proliferate. Many materials make good mulch, including compost, fallen leaves (except ones with disease), bark chips, rice hulls or alfalfa hay. Be careful to keep mulch 4 to 6 inches away from the trunks of plants to avoid crown rot.

    • Plant a cover crop. A cover crop, also known as green manure, is typically a legume planted from seed in the “off season” to improve the condition and fertility of the soil. Legumes such as fava beans, crimson clover and vetch release nitrogen from their roots into the soil over the winter. Decomposed cover crop materials provide nutrients directly into the soil, thereby increasing biological activity, water infiltration and soil tilth. Some green manures have roots that can reach down much deeper than any shovel or rototiller, so in essence they’re doing much of your dirty work. Taller cover crops can be weed whacked or mowed, lower varieties can be turned right under. An added benefit is that there is no chance of nutrients being washed away since all of the action is happening underground. Microbial activity is maximized and ultimately supplies food for the earthworms that are critical to soil health. And a bonus is that while your soil is enjoying the benefits of cover cropping, your back will be happy to know that many weeds are being smothered or eliminated.

    • Prevent fungus from developing by cleaning plant and leaf debris that has fallen and is collecting on the soil. Leaf debris is fine for mulch, but after you have protected your soil with compost.

    • Prevent petal blight by picking off old flowers, especially in camellias, and place in green waste, but not your home compost.

    • Think twice about using chemical remedies for garden problems, as they may have unintended consequences.

    • During the winter months, do not disturb the soil — no tilling, digging or walking on it. Healthy soil is about 25 percent air, which encourages root growth. In the spring, if you planted a cover crop, you can till the legumes into the soil or skim off the tops and add them to your compost bin.

    Taking the extra effort to be vigilant with your soil in the fall makes it easy to begin growing the following spring. Your soil will be teaming with life and ready to receive your new plants.