The Importance of Soil pH to Gardeners
Soil pH may not sound the most exciting thing to a gardener but it’s essential to get it right for many plants to flourish.
You’ve probably heard of so called ‘lime hating plants’ and maybe even know which ones these are. But do you know that there are many plants that grow better when the soil has lots of lime in it and has a high pH?
Winter is a great time of the year to delve into this more technical side of gardening and to put things right if needed.
What is Soil pH
Before we do that, we need to understand soil pH. I’m sure that you will know that pH is the symbol used to indicate whether a solution is acidic or alkaline.
A neutral pH is 7 but in practice for gardeners we tend to regard neutral as pH 6.5. This is where the majority of plants will be happiest and will be able to access the nutrients they need.
If you want to get technical pH is a measure of free hydrogen and hydroxyl ions in a water solution. The pH scale runs from 0 to 14 but in practice most garden soils will be in the range of 5 to 8.
So if your garden soil has a pH of below 6.5 it’s regarded as acid and above 6.5 it’s alkaline.
Why is pH important?
Well certain nutrients are more readily available to plants at some pH levels than at others. In addition to this some diseases are more prevalent when soils with an incorrect pH.
Let’s look at so called lime hating plants.
Perhaps they would be better described as “acid loving” because they grow best when the pH is below neutral.
Most of these are in the heather family [Ericaceae]. Think Erica, Calluna, Rhododendron, azalea and Pieris.
Camellias are often lumped with ericaceous lime hating plants but in my experience they are far more tolerant of soils closer to neutral. Nevertheless, they thrive in acid soils.
The same could be said of most Magnolia trees. However some magnolias such as Magnolia kobus are actually lime tolerant so that’s why in spring you see them so widely planted in Britain.
A few edible plants prefer an acid soil. You might not have thought of blueberries and cranberries [Vaccinium]. They need a very low or acid pH. These are in the heather family too.
Potatoes prefer soil pH that’s below neutral as do aubergine and sweet potatoes.
Raspberries, blackberries and strawberries prefer a slightly acidic soil.
But what of those plants that like soil pH above neutral?
Well there are masses of these and they tend to be taken for granted. There’s some magnificent lime loving plants!
Just think of Clematis, hellebores, lilac, Euonymus, honeysuckles, passion flower and lavender. I don’t have room to list them here.
As for fruit plants there are lime lovers too. Fig, grapes, cherries and plums like an alkaline soil.
All the cabbage family likes alkaline soils. So that’s sprouts, cabbage, swedes, rocket, pak choi, broccoli, cauliflower and even wallflowers.
Maintaining soil pH above neutral is especially important in combating the root disease ‘club root’.
Check it out now
So with this in mind and especially in planning my new garden I’m checking my soil pH this week. I’m using a readily available soil pH testing kit. It’s is easy to use and gives a result in minutes.
I’ve also got an electronic pH gadget that gibes me an instant readout.
World Soil Day
With World Soil Day on December 5th there is no better time to take a closer look at soils. We need to understand where and what to plant but may also need to apply lime to get the soil pH right for planting and sowing in the next few weeks.