Dirt, From the Ground Up

For most of us, winter has officially taken hold of the garden.  If you are like me, you occasionally sit by the window on frosty mornings peering out at seemingly empty spaces. Thoughts and daydreams fill the mind: sprawling vines, towering sunflowers, baskets of fresh picked fruits and veggies, waves of colorful flowers enhanced by fluttering butterflies, birds and bees. You comb over seed catalogs, draft planning designs,
determined to make a showing that would leave Martha Stewart without words.  Now just for a moment, let’s put those catalogs and plans aside.  Go back to the window and look.  What do you see?  A blanket of snow?  Remaining mulch from the year that has gone by?  Or just bare dirt?  If you gaze upon the latter, this article is especially for you.

A lot of people see dirt as just that: “dirt”. In my fifteen years of working as a professional gardener, I’ve found the least understood aspect of my clients’ gardens to be the ground below their feet. The earthen ground seems benign and indestructible to many people.   If you’re looking out the window at cleanly raked, bare soil this winter, then you are likely doing the land a disservice.  If you want to make those dreams of garden grandeur come true, then this year: start from the ground up.

Dirt, you see, is a living, working system. It takes time to build—years—but can be destroyed in an instant. I tell people all the time, “Keep it covered, keep it protected”. Bare ground is susceptible to erosion. Wind and rain not only remove soil but their forces destroy the structure, sifting small particles upward, removing pore space and creating a crust impenetrable to air and water. Protected under mulch that absorbs the impact of rain, beneficial microbes and earthworms work tirelessly to construct soil into an arrangement of various particle sizes interspersed with pore spaces and tunnels. Pore spaces allow water and air to percolate down to the roots. When water moves down through the soil, it creates a vacuum, drawing air behind it, pulling needed carbon, oxygen and nitrogen gasses along with it too. These gasses are the building blocks of life. Interestingly, these necessary elements are brought in from gasses, not from the soil itself. Un-mulched soil is also exposed to UV light that kills our beneficial microbes. Un-mulched soil dries out faster, again harming microbes that are so important to creating a good layer of humus and good loamy soil structure. Ideally, your mulch should be matched to the types of plants you are growing. However, something is better than nothing, even if it is just shredded leaves or straw. Basically, a garden without mulch is like leaving a lid off a jar. The contents will evaporate or go bad.

Good soil structure is important because the structure dictates how soil performs,
like how well it retains moisture and nutrients. Sandy-textured soil is mainly composed
of large particles. The structure of a sandy soil does not retain moisture and nutrients well since the pore spaces are so large. On the other hand, clay-textured soil is composed of very small particles that fit close together (picture in your mind dinner plates stacked
in a cupboard). This holds on to water and nutrients but may not allow for good drainage. Optimum soil composition is a balance of the two known as loam, the combination of clay and sand particles will provide some drainage but retain some moisture and nutrients.

So now, it is spring. You have some mulch on your garden and you are ready to plant. Here’s where you are going to rake that material away for a moment. I always try to keep un-decomposed material out of my planting-holes but remember to put it back when you’re done. Mulches tend to be high in carbon. Mixed into the ground, they may be slow to break down or not break down at all. They likely bind nitrogen, removing its availability from the plants.

As spring gives way to summer, the ground really benefits from a covering of organic material to aid in moisture retention and protect from exposure to weather extremes. Seeing cracking in your soil during summer is a worst-case scenario and means you need mulch immediately. In the hot summer months supplying organic nitrogen sources or compost during the growing season will help break down mulch into humus adding a loamy structure to the soil. Avoid synthetic salt-based fertilizers which may burn plants or run off into the groundwater being as they are water-soluble and have no real benefit to the soil. A good balance of compost and mulch or nitrogen and carbon on top of the ground will decompose naturally, building the soil, not destroying it and feeding plants naturally.

When fall arrives and the leaves begin to fall, we take to cutting back and cleaning up. Shred or compost your organic matter. Reuse it next year. Don’t send it to the curb for pick-up! It takes enormous amounts of energy and time for plants to create this organic material from raw minerals. As a sustainably minded gardener, I strive to reuse everything on site. It cuts back on the cost of buying mulch and fertilizer and time spent watering throughout the year. A well-kept garden has always began with well-kept soil.

4 thoughts on “Dirt, From the Ground Up

    • Probably not the best. It would block rain from getting to the soil, won ‘t decompose to provide an organic humic layer and may even offgas chemicals into your soil as heat and UV light break down the tarp.

    • It also depends on how moist your compost pile is. If you get a lot of rain you’ll want to cover your pile so it doesn’t get soaked. If you pick up a handful of your compost and squeeze it it should be moist but you shouldn’t be able to squeeze any water out of it.

  1. Nice article! I think covering your garden with a blue tarp is a bad idea too…it would leach all sorts of nasty things into the soil pretty quick under those conditions along with blocking all the great stuff like organic matter, sunlight, and water doing their countless jobs. As far as a compost pile, wouldn’t cardboard work for deflecting excess rain from compost and add carbon to the pile?

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