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Winter Soil Health - cover crops, leaf mulch & more!

Updated: Sep 28, 2023

Fall and winter weather can be rough on our PNW garden soils. Continual rain and fluctuating temperatures can cause soil runoff, loss of nutrients and deteriorate soil structure. Soil organisms rely on healthy soil structure and plant roots to survive and continue to process organic matter into healthy soil.

Fava bean flower

How you protect your garden soil (and soil buddies) in fall and winter will make all the difference next spring! For my coaching clients I always suggest that they plant a fall and winter garden - there are so many things we can grow over winter here in the PNW (read my fall and winter gardening guide here)! However, there is still occasionally at least one or two beds (or sections of the garden beds) that end up empty as of late fall. In that instance, I suggest seeding some cover crop.


The best and easiest cover crops for urban gardens are legumes

I prefer to use legumes, specifically fava beans, field peas, and crimson clover. There are other types of cover crops but I have found these to be the easiest and most beneficial for urban gardeners. Here's why:

  • Legume magic: Generally, after Summer and Fall crops are done growing your garden soil is fairly depleted of nutrients, mostly nitrogen which also easily leaches from the soil. Legumes partner with soil bacteria that fix nitrogen from thin air (no really) and feed it to the plant. The plant provides the bacteria with carbon. What a great partnership!


  • Green manure: Come spring the green growth of the cover crop gets "turned in" to the soil (or cut at the ground level and added to your compost bin). Using the green growth and composting in place (turning it into the garden bed) acts as a "green manure" as it breaks down/composts in place and provides organic matter for the soil organisms to munch on!

  • Easy germination even in colder temps! You can cover with fabric row cover to speed up germination.

  • All of these make it through freezing temperatures and even snow! Some will die back but they will quickly resume growth once the snow melts.

  • Pea shoots from field peas are a great edible winter crop!

  • Blossoms of crimson clover are wonderful for early pollinators, plus have medicinal uses!

Here's a video of me chopping in field peas in the spring. Larger areas are best chopped with a shovel. Just chop it in, do not turn over the soil. It's ok if some still remains visible on top. You are basically just composting in place:


KEEP YOUR SOIL COVERED!

Fall garden bed ready for winter
Other types of soil coverings include:
  • Overwintering plants (leave your fall crops in the soil: kale, broccoli/cabbage/cauliflower stalks, even dead and spent plants are beneficial for soil and provide habitat and food for birds and beneficial insects)

  • Fall leaves

  • Organic Straw (no hay!)

  • A mixture of above (see photo below)

  • Fabric row cover (see resources below)

This is where lazy gardening really pays off! Leave the leaves, don't pull spent plants - the natural system works well: fall leaves provide soil cover and food for soil organisms.... don't mess with perfection!

In the early spring, if the organic matter you used is broken down enough you can put your new compost directly on top and it will continue to break down and be ready to plant new crops in.


If you have too much straw or leaves, remove some and relocate to a pile to continue breaking down. I make round "bins" out of chicken wire and stuff them full of fall leaves. Composted leaves make great mulch!


Thank you for being a soil protector, your garden will thank you later! Fall and winter is a great time to plan your garden for next year. An in-person consultation from Marni will give you personalized recommendations based on your growing conditions and preferences! Contact Marni at GrowingRootsTogether@gmail.com for more information and to set up a FREE 15 minute phone call.


 

More cover crop info and seeding info:


Resources:

Shop Garden Starts, herbs, and food forest plants: Growing Roots Together

Fall & WinterCover crop seeds: Organic fava bean 'Sweet Lorane' and Austrian Field Peas at your local nursery or Territorial Seed Co.

Organic Straw: Walt’s Organic Fertilizer Co, Seattle

Burlap bags: coffee roasters, Ace Hardware (call)

Boxes/leaves: Neighbors, Facebook Buy Nothing Group, Nextdoor.com

Metal Hoops/Row Cover/plastic sheeting: Sky Nursery, Gardeners.com, Johnnyseeds.com





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