Planting in clay

People who live in the city are funny.  Many of them look at nature as something that needs to conform to their designs.  They build lots of concrete buildings and they have asphalt everywhere.  They have some parks, filled with grass.  They have rainstorms and then it floods, or the trees that they plant die when the ground becomes saturated.  A few years ago a friend had a problem with drainage in his backyard and I told him not to dig it up, but to plant a tree, the right tree.  

I was just in a park that was suffering from standing water and it had been planted with a hundred seedlings of various types, all the wrong types.  If the land dries out, they will do okay, but if it doesn't, they will die.  People want to plant the tree that fits their idea.  They want to plant tall columns of evergreens because it is all contained and the foliage is tight and prevents people from intruding, but they have clay soils and the plant they are choosing do not work for the area.  

When you plant a tree you should plant a tree that will live in the area and thrive, but if you want to plant your tree that you want you need to alter the conditions of the area that you are planting in.  Planting native trees is often the best thing to do, but there are often a variety of non native plants that will change the growing conditions of the area, to allow other types of trees.  

In areas that have poor drainage or excessive dampness, a willow is an ideal type plant.  They normally grow on rivers and so their roots can survive in wet soil.  They will grow fast and soak up the water of the area too.  In a forest or a park I would pick a golden willow that will grow to dominate the area for more than a century, but in a backyard, I would pick a Japanese Painted Willow, whose foliage is pink turning to white and green, or perhaps another dwarf type willow.  Often a backyard will only need one willow to soak up the water and allow other types of plants to flourish.  Willows can come in many sizes, from two meters tall to forty and all sizes in between.  If you are looking for a privacy screen, chose the white cedar, they can grow quite close together and they will grow in permanent standing water, like swamps, so they work in the wettest of backyard conditions.  When I say they can be planted close I mean right on top of each other, but is you are making a hedge, try to keep them at least 15 cm apart.  Unlike many evergreens, white cedar are quite resilient to damage and winter kill.  Many times when people plant a shapely Emerald Cedar, they get a red and dead plant, or some animal will graze on it and it will be dead.  Not so White Cedar, they come back next year.  

In the area I live there is a lot of heavy clay in the soil.  Clay prevents water from permeating the ground and it will enter the hole where your plant sits and not leave, choking the roots and killing the plant.  When you live in a clay belt, it is important to look at the plants that grow well there.  Certain plants do better in clay, like Silver Maples, Red Oaks, and several others.  Plants that can take a lot of water at their roots.  

In clay soils and in areas that flood in rainstorms, it is important to know that there are things that you can do to reduce the surface water accumulating.  Grass helps but only compared to bare soil and asphalt.  It you want to increase the infiltration of water into the ground you need to provide pathways into the ground.  Shrubs and trees are orders of magnitude better at channeling water into the ground than grass.  Water will sink though the holes in the clay and ground that tree roots have made.  Remember the simple rule, the mass of a plant above e ground is proportional to the mass below the ground.  Big trees can shunt more water into the ground than small plants.  

In clay there is only one sure way to get rid of it, other than removing it and replacing it, and that is to add organic matter to the soil.  Organic matter will break up the clay and mix it into the new, making a better soil than you had before.  All plants have roots and the roots grow and die all the time.  The dead roots decompose and mix with the clay, making a better soil.  Small plants change the soil in this way only on the surface and bigger plants deeper still.  This is called soil management and it is something that farmers did unconsciously for centuries.  That is what you want to do in you backyard too. You can add organic matter to you soil yearly and artificially to create better soils; it is a long term project that can feel like it will never end, but gradually you will see differences.  You can add leaf litter to the ground, you can compost and add that too.  You can add manure and other soil products too.  And there is one last thing you can do, if you have to—add Horticulture Gypsum to the clay soil and this will allow the freer flow of water through the ground, but doing this will do nothing to change the soil permanently and will need to be redone every 2-3 years.