Garden Winterization Techniques

The last of the summer crops are harvested. There is a tangle of dead and dying foliage and a few weeds hiding among the remaining carrots. The nights are cold and the rains are coming soon.

Now what? 

Your soil has been working hard all season. It’s time to protect it from the pounding rain, winds, and frost.  We also need to keep our soil microbe friends fed during the long winter months. The NRCS has excellent guidelines for protecting soil health.

NRCS Principles for Soil Health

1. Use plant diversity to increase diversity in the soil. 
2. Manage soils more by disturbing them less. 
3. Keep plants growing throughout the year to feed the soil. 
4. Keep the soil covered as much as possible. 

Lime: Our rainy winters are notorious for leaching minerals from the soil. A light dusting of lime on garden beds and fruit trees, (but not on natives or acid lovers like blueberries!) will break down during the winter and assure a neutral pH for spring planting. Do this in addition to choosing your preferred method below.

My Favorite Method:

1. Cut spent vegetation to soil level and distribute veggie matter on the garden bed.
   1. The roots decay, feeding microbes and creating pore space. 
   2. Remove any diseased material from your property.
2. Spread on a layer of fall leaves.
   1. Worms will dine on them all winter leaving nutrient rich castings. 
3. Cover leaves with a thin layer of compost.
   1. Keeps the leaves from blowing away and restores P and K levels as well as other nutrients and minerals.
4. Sprinkle cover crop seeds. (I like to use cold hardy mix from True Leaf Market.)

A Bird Friendly Method:

1. Leave crops with seed heads in the beds.
   • If your lettuce, herbs, flowers, and other crops have put out seed heads, it is entertaining to watch goldfinches and juncos dine on them all winter. The roots rot naturally in the soil and the vegetation provides some protection from the rain and wind. 
2. Distribute compost at the base of the plants.
3. Sprinkle cover crop seeds
4. The chaff can be removed late winter, or hoed down with the cover crops when preparing the bed for planting.  (More bird friendly tips.)

Even Easier:

1. Leave your garden messy all winter, and let nature do her thing.

The Worst Method:
Sadly I learned this one through experience. Pull out all the plants and leave soil exposed all winter. By spring my beds were barren and compacted. I had no choice but to spend several backbreaking hours turning the soil and amending it. I was surprised to find almost no worms or other signs of life.

By contrast, now when I roll back any leftover debris to prepare the beds in spring, there are worms peeking out of burrows under nearly every leaf, and the soil is fluffy, rich, and teeming with life.   

The City Beneath our Feet: A Soil Health Primer

Soil organisms use the inert components of soil (sand, silt, and clay) to build structures, like vast apartment complexes. Their cities have air and water moving through them. There are subways, and communications networks, nutrient distribution, and trade systems. It is very organized and resilient, yet delicate at the same time.

The tiniest varieties of these bacterial city dwellers occupy porous spaces in the soil eating organic matter and storing nitrogen in their bodies, while larger organisms such as nematodes, rove about eating any wayward bacteria that venture out of the safety of their soil pore apartment. Nematode excretions leave the liberated nitrogen behind to be wicked away by other organisms.  (Which accounts, in part, for the burst of fertility after tilling.)

Earthworms are part of the megafauna of the ecosystem. They bore huge mucous lined tunnels through the city that hold air and protect the soil from dissolution in water.  In their pursuit of organic matter to eat, (they especially love fall leaves) they leave behind castings touted to be the world’s richest fertilizer.  

Mycorrhizal (fungal) filaments are the communication and delivery system of the underground.  These powdery tendrils reach deep and wide to mine nutrients from subsoil and transport them in exchange for the one thing it can’t do for itself–harness energy from the sun.  Recently, trees have been discovered using their mycorrhizal network to send alert messages to surrounding trees and even deliver sugars and nutrients to trees that are suffering from disease or pests. (http://www.bbc.com/earth/story/20141111-plants-have-a-hidden-internet)

When a seed is dropped into a functional soil ecosystem, this sand-silt-clay built city is eager to offer its many services. In exchange, plants deliver a significant portion of the sugar, amino acids, and other compounds they make during photosynthesis to feed the inhabitants of the soil city. In this way cover crops feed microbes all winter. 

Understanding that there is a city beneath my feet has completely changed my attitude towards how I manage garden ecosystems.  I’ve caught myself apologizing when my foot depresses into its soft spongy surface. I no longer rip plants out at the end of the growing season, but I let them stay and rot creating food and porus spaces for my tiny associates. I make sure the city is protected and its inhabitants well fed during the winter. Tilling this fragile city seems unthinkable.  Tilling destroys their pore spaces, breaks up the soil aggregates, exposes beneficial bacteria to roving nematodes, chops up earthworms while they benevolently work for free.  

In our gardens, let’s give these microscopic workers shelter from the pounding rain, winds, and cold. Let’s provide them with ample food: the leaves, compost, and plants that will harvest the sun’s energy for them. In turn our soil engineers will continue construction of their subterranean city and enrich our depleted soil for planting in the spring.