Acid remarks over soil pH
Knowing the pH of your soil is vital so you know what you can – and can’t – grow. This is where soil testing comes in, and it’s very easy to do. You wouldn’t buy a house without knowing whether its foundations were solid. However, most of us never bother to check whether our soil is suitable for the plants we want to cultivate.
Many years ago, I failed to grow a Rhododendron. This genus (plus azaleas, hydrangeas, and heathers) includes acid-loving plants. They hate lime, so I guessed my soil must be neutral or slightly alkaline.
After learning my lesson, I now have a wonderful Rhododendron called Goldflimmer. It has purple flowers and variegated foliage. To boost the acidity in the soil, I give it an ericaceous slow-release feed in spring. I add a mulch of ericaceous compost in spring, topping that up after Christmas with the needles from the Christmas tree. Trust me, it works! Here are other things you can do with your old Christmas tree. Experts are warning gardeners not to add bonfire ash to their garden soil.
A basic soil testing kit will save you money
After my initial failure, I bought a small pH test from the garden centre. It’s easy to take a sample, mix it with the chemicals and compare the resulting colour with the chart. There’s a comprehensive list included of what does best on acid, neutral or alkaline soils. There are also suggestions on how you can improve the soil that you have.
My soil ranges from pH 7 (neutral) to 7.5 (alkaline), which is a decent value for most things. If you want to grow lime haters, use ericaceous compost in large tubs or raised beds.
Soil testing – Plants for alkaline or chalky and limestone soils
Chalky (and often limestone) soils are alkaline, and the opposite of acid soils, on 7.5 or above if you do a pH test. They are free-draining, so are drought-prone and lacking in nutrients. Your best bet is to think Mediterranean – plants that thrive in dry summers, need good drainage and moderate to low fertility.
If you have some clay in the mix, your soil’s nutrient levels will be higher, and its water retention, too. However, some chalky soils are incredibly shallow, making the normal planting of shrubs impossible without adding raised beds or adding huge quantities of topsoil. The RHS has a comprehensive list of suitable plants. Establish how alkaline your soil is with a pH test and dig test holes to find out how deep it is before you hit bedrock.
