Creating flower beds from scratch in clay soil

(Question)

I have a problem with a piece of land on my property which is all clay. We want to cover part of it with grass and create some beds and then plant flowers and shrubs.  Do we have to dig deep and take out that clay soil or can we just put some topsoil and triple mix on the top of that and then plant.

 

(Answer)

The most important thing to remember is that a successful garden will greatly depend on the quality of the soil. There is no doubt that gardening in clay soil can be a challenge. Clay is considered a heavy soil and is hard to work with, especially under wet conditions. Clay soil is very slow to drain after rain. It compacts easily and in dry weather it bakes hard and cracks. Furthermore it warms up slowly which can delay plant growth. While it may be wonderful to start a garden with a clean slate, removing your clay could be quite a labour intensive project. Furthermore, the costs involved and the length of time this may take should not be underestimated.

Mark Cullen comments that “if your soil is so hard and clay like that you need a pickaxe to dig it, you will need to remove it to a depth of at least 18inches for annual and perennials and 2 feet for evergreens, shrubs and roses”.  Depending on the size of the beds you plan to create this could be a daunting task. How will you dispose of the clay soil? Have you got a strong back for all the digging? Are you prepared to hire a landscape gardener? Hopefully, your property is not in such bad shape and all you need to do is amend the soil.

You have the right idea by thinking you can put topsoil and/or triple mix right on top of the clay but it’s not that simple. The best time to start this project will be in the Fall. First, you will need to clear away any existing vegetation covering the area you plan to plant. One method is to smother it with newspaper. A layer of five sheets is usually thick enough. Then spread a thick layer (4 inches)of compost, triple mix and/or topsoil on the newspaper and wait. It will take about four months to decompose. At this point you should add more topsoil, then dig it in and turn it over before planting. You will in effect create a raised bed. This method, from experience, is quite effective for smaller flower beds, especially if you are prepared to wait. If you are planning to create large flower beds then use a rototiller to break up your clay soil and then add topsoil or triple mix and dig it in.

To ensure your soil remains fertile and healthy it is best to add organic material such as compost and leaf mould on a yearly basis. This will keep your soil workable. The good news is that there are plants that do well in clay like soil such as roses. A Google search on “plants that grow (or thrive) in clay soil ” should bring up lists of suitable plants.

Here are links to three articles with good information on gardening in clay :

http://www.finegardening.com/improving-clay-soils

http://extension.missouri.edu/p/G6955

http://www.ces.ncsu.edu/depts/agecon/WECO/documents/NCSU.amending.clay.soils.pdf

And please see this link which is a similar question from our website:

Amending Clay Soil