A brief video on how I overcome having only a few inches of topsoil in my lawn, under which is this blog’s namesake – Black Gumbo clay. This stuff is extremely dense and does not drain well. I have dug holes, seen them fill up with water, and remain with water for more than 10 days. And it was largely evaporation, not drainage, that reduced the water. How can we plant trees in such terribly soil? My video explains what I do.
As an additional note, digging a hole and filling it with water is a good way to test your soil to see how good your drainage is. If it is empty in an hour or two, your soil has the qualities to be called “well drained soil.” If it takes longer, start researching for solutions and workarounds, your soil is problematic.
Try the test in different parts of your yard. Different spots on the same property, even within a small lot like ours, will have different traits. The reason for this, in my typical Houston-area subdivision, is this: When they cut our streets in, the natural black gumbo clay layer was bulldozed up onto the home lots to form pads. These pads were shaped to leave a four to five foot differential between our home foundations and the street. This allows for quick drainage of the neighborhood, making the streets like flash-flood rivers when the frequent heavy rains come. Our street has been raging rapids many times. Likewise, the builders left shallow channels between the houses to direct water from the highest points in our back yards down to the street. It is very evident during a flood how the structure of our lots and streets were wisely considered.
But for planting shallow-root trees and bushes, that’s not so great. So what we have is a two foot clay cap that was naturally occurring, plowed up from the streets and flipped onto the lots, leaving us a three to four foot layer of black gumbo clay to deal with. If you can get beneath that three to four foot layer, there is a layer of very well-draining sand, and beneath that sand, wet iron-rich clays and sands and lime gravels, even some brackish water intrusion since I am close to the coast. Our oak trees and various well established tap-root trees go well into that layer. The builders planted oaks with large excavating equipment that penetrated the clays to access the moist sands, insuring everyone had a successful oak tree in their yard.
Considering how I do not have heavy equipment, I have to make things grow on top of the clay. That means a shallow rooting tree like a fig tree needs a little help to get established in the upper inches of topsoil. Once it is established, it begins the slow and hard work of invading the gumbo clay.
It also means that when a tree has run its life cycle, from 30 to multiple centuries, an you happen along when the tree is rotted or uprooted by a hurricane, the former footprint of that tree will make deep, loamy soil once the roots have decayed. That’s a good place for a new tree!
Have a look at the video, it will help if you have similar conditions and want to plant a tree in your lawn.