By Jez Clark
Chalk House – Native Garden Project Part 3 – Soil
A key factor when determining your garden design is to assess your soil.
It’s worth spending some time digging some spade-depth holes around the garden to check for rock and compaction.
Depending on where you live on the mountain you may have deep soil or what we call skeletal soil, heavy clay and rock.
The traditional method of testing your soil is the ribbon test. Moisten a handful of soil and roll it into a ball, then into a ribbon between your thumb and forefinger.
Texture tells all, if it feels gritty and falls apart it is sandy, if it feels sticky and rolls easily then it is clay, if it holds its shape but gently crumples lucky you, you have a loamy soil. The mountain soil is usually clay with varying degrees of heaviness.
To determine the heaviness of your soil you can also to a simple drainage test by digging small percolation holes to a depth of 40cm, fill with water, and let it drain overnight. Refill and time how fast it drains.
Fast draining suggests sandy soil; slow drainage indicates heavy clay.
It’s also worthwhile checking the pH of the soil.
You can buy test kits that a have easy to follow instructions. In general, the mountain soils are acidic with a pH ranging between 5.0 and 6.0.
Knowing your soil pH will help you determine the right types of plants to grow.
Some, like hydrangeas and camelias love acidic conditions while others like lavender do not.
It is possible to ameliorate your soil with lime to reduce acidity, but I always suggest working with what you have.
The acidic soil also tends to be low in phosphorous which is ideal for growing native Australian plants such as grevilleas and banksias but can be an issue for other exotic ornamentals and vegetables. Be careful when using fertiliser.
If you have native plants do not feed them with a traditional high phosphorous fertiliser as they will suffer toxic shock.
Look for products clearly labelled as safe for native plants, or fertilisers that contain less than three per cent phosphorous.
Visit Clark+Granger at www.cplusg.com.au or phone 0456 111 120 to find out more.
