A solid foundation is the key to the long term success of your rock garden. You can spend days or even months planning and constructing an esthetically beautiful rock garden only to see the plants die and the garden be reduced to a muddy mess due to a lack of drainage.
As with many other things in the world, a thoughtfully constructed dirt foundation is critical to the success of your rock garden. You might think that you have found the perfect natural slope on your property for the garden but I still advise that you grab your shovel and dig out the area of the garden and create a proper foundation. The issue here isn’t the slope. It is the fact that plants typically used in rock gardens require soil that both retains water and provides adequate drainage.
There are four steps to creating a rock garden foundation:
- Dig: Once you have settled on the site of your garden, it is time to start digging the foundation. I suggest that you begin by outlining the area of the garden with posts and string to prevent superfluous digging. Dig down to a minimum of 1 foot and be sure to pull any remaining roots and weeds.
If you can’t find a good slope on your property then you can create what is known as a raised bed which is basically an elevated garden above a rock or concrete wall. For raised beds, I recommend digging down to about 3 feet. Just fill in the dirt as you build the garden’s walls.
- Lay The Drainage Layer: The drainage layer is the first part of the foundation that you will lay into the ditch that you dug out. For this layer, use a mixture of rocks, broken bricks and concrete and pieces of clay pots if you can find it. The drainage layer should fill the ditch about 1/3rd of the way.
- Lay The Sand Layer : Next to be put in the ditch is a thin layer of sand (3-4 inches) Sand holds up the top layer of soil and allows excess water to drain.
- Lay The Soil Layer : The soil layer is the most critical layer of the foundation. It is important to create a soil mixture that is appropriate for the plants and flowers that you intend to plant in the garden so as to allow your garden to achieve its full potential. The mixture that I use in my rock gardens is an even mixture of topsoil, gravel and peat.