Don’t get me wrong – I love most things about gardening in the southeast US. But heavy soil is a burden we must bear, in exchange for skin-plumping humidity and relatively mild winters. If you want to grow anything over the long haul in these soils, it’s wise to develop a strategy that puts them to work for you. You’ll often read that clay or gumbo soils benefit from the addition of organic matters (OM) to improve drainage. That’s true, but as you are out there preparing a new bed or rejuvenating an old one, you might like to know why you’re making all that effort.

 

Clay soils literally come packed with all the minerals plants need, the ability to bind molecules tightly together, and incredible water holding capability during dry times. That’s the good news, but given all the rain our region gets in an average year, it can be a mucky liability. If you use even recommended amounts of chemical fertilizers, some nutrients can build to toxic levels in the soil over time because pure clay captures them. The addition of organic matters such as compost, ground bark, and other half-decomposed natural materials makes at least 3 significant changes in native soil.

 

1) om gives the tiny particles of clay something to hold onto, which

2) opens the soil spaces so water and air can flow through, which

3) allows roots to reach further into the soil to obtain water and nutrients.

 

Indeed, organic matter itself is rich in nitrogen and other essentials, so its presence in the soil adds to their availability without building levels beyond plants’ tolerances.

 

Choose to use several different organic matters to gain different sizes and rot rates in new plantings. For example, fully developed compost is about the size of coffee grounds, while the leaves you piled up last year are larger and still decomposing. Ground bark products are rotted enough to incorporate, and take the longest to finally become one with the soil. The mulch you lay atop the bed will rot, too, and should be worked into the top of the bed unless it is pine or other straw or bark nuggets. Replace those when they lose their color or become matted. In most situations, a shovel’s depth of soil is plenty when combined with four inches of organic matters to create a bed that is slightly raised. The materials do settle, but a couple of inches above flat ground level benefits most garden plants. Use a lesser ratio of native soil to om when digging a hole to plant a single tree or shrub, especially native species. Your goal should be to improve the initial growing site without making it so perfect that the tree’s roots grow in circles inside it instead of penetrating into the native soil eventually.

 

The photo accompanying this column is an icon in the neighborhood. There are actually 2 of them on opposite sides of the road and they shift their tilts along with wet and dry years. Clay shrinks in drought, and when it is rewet, swells back up to one unpredictable extent or another. When you realize that this concrete pylon can be lifted and dropped by soil dynamics, it’s easy to understand what can happen to plants. Even the mightiest oak’s roots are no match for unamended clay where water management is left to Mother Nature.

 

Happy Holidays to all – give yourself the gift of OM!

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