When I moved into my 1901 Queen Anne home, I inherited over a century of previous homeowners' yard maintenance practices or lack thereof. My front yard had decent looking topsoil but it was very compacted. Whenever it would rain, it seemed that the water would just run off. It was very difficult to grow anything successfully. One of the more noticeable features is a Willow Oak that is probably as old as the house or close to it. The back half of the property was a jungle of non-native invasive plants. After removing this jungle and several decades of dumped items such as tires, cans, and bottles and more, I found that the soil here was rich and deep. I could dig down a foot and a half before I hit clay. Things grew well and when it would rain, the runoff was greatly less than the front yard. This got me to thinking about why and how to use this knowledge to improve plant survival success.
My background is that my dad worked for the Soil Conversation Service for 25 years. So I grew up hearing about soils and conservation and ecology from a very early age. I know soil is made up of sand, silt, and clay in varying degrees. It also should have organic material in it. Good healthy soil should have an organic content of 3-6%. How loose or compacted the soil is is based on these four components in addition to mechanical compaction from human interaction. In our area, organic material breaks down in about three years. Traditional landscape practices are to cut back grasses and perennials, rake up the debris and leaves, and haul it away or dump on a compost pile. For the health of the soil, this may be the worst thing you can do.
As a tree/plant grows, it takes up nutrients in the soil. The plant uses this for its growth and then when it drops leaves, the nutrients are dropped to the ground as well to be used again by the plant. However, we often haul all this organic material away, so the tree/plant finds more nutrients in the soil to use and the process repeats. Logic would tell you that you can only do this so long before most of the nutrients in the soil have been hauled away in our fastidiousness of cleaning up our yards. As the organic material is depleted, the soil continues to collapse and can absorb less water as it does so. Healthy soil becomes dirt that can no longer support a healthy ecosystem.
The typical homeowner tries to make up this practice by mulching every year. Typically mulches need to be 3’’ deep to keep weeds down and to hold moisture. After years of doing this, a deep top layer is formed that often is hydrophobic. Bark mulches do add organic material to the soil but break down relatively slowly.
So I began experimenting with using a thin layer of aged compost as a mulch in my more manicured areas of the yard. Anywhere that I can do so, I have planted plants that leaves can fall down into and stay hidden and allowed to decompose. My pollinator garden plants are left standing all winter and then cut back just before new spring growth. Those are laid down in the bed so that the new growth can grow up through the “debris.” This becomes a natural compost mulch. The areas that I use compost as a mulch I often just spread it over any leaves that may be there. This keeps the beds looking tidy without hauling away all the good free organic material. The results so far have been good. While the compost can also become dry and hydrophobic during hot dry spells in the summer, overall, I get much better water absorption, the beds look like someone cares, and I avoid the build up of years of mulch.