Soil PH levels in your garden and why they are important

It’s incredible just how many different plant varieties we have available to buy and plant in the UK. Even more incredible when you look at the number of variations and hybrids there are of just a single plant. The “back in fashion” Camellia for example has around 300 different classified varieties, with up to 3000 additional hybrids.

When you think that some of these plants originate from places as far away as Japan and South America, it’s easy to see why some plants you might put into your own back garden, never really thrive and reach their full potential.

Weather conditions, frost, sunlight (or lack of) all play their part, but so does the soil PH levels in your garden.

You may have heard people talk of “acid loving” plants or “plants better for alkaline soil” and this is all to do with the soil PH levels. You may remember from school, dipping litmus paper into different solutions, to see which ones are more acidic or more alkaline, well soil works in the same way.

If you live in a really chalky area for example, you may find that your soil ph levels are as high as 8 (alkaline) and it’s important that you know this because you’ll need to choose the right plants for your garden. You can add and reduce the acidity of your soil but in general, it’s always better to work with what you have (unless levels are excessive).

Below is an image of the acid – alkaline scale, to give you a rough idea of the different possible variations. In reality, you’re obviously not going to find your soil anywhere near the top or bottom of the scale. However, if you have soil with a PH level of 8, that’s not going to be a healthy environment for acid lovers.

Below the image is a small list of common plants and their preferred PH levels. This will just give you a basic idea of the kind of plants that suit different soil types. Planting a Rhododendron in soil which has a PH level of 7, is risky business and it might be you have a few plants that are not growing too well. If you check your soil PH level, it may reveal a problem you hadn’t previously considered.

Soil PH Levels  Common Plants and their preferred PH Levels:

  • Trees and Shrubs
    Apple 5.0-6.5
    Ash 6.0-7.5
    Azalea 4.5-6.0
    Basswood 6.0-7.5
    Beautybush 6.0-7.5
    Birch 5.0-6.5
    Blackberry 5.0-6.0
    Blueberry 4.0-6.0
    Boxwood 6.0-7.5
    Cherry, sour 6.0-7.0
    Chestnut 5.0-6.5
    Crab apple 6.0-7.5
    Dogwood 5.0-7.0
    Elder, box 6.0-8.0
    Fir, balsam 5.0-6.0
    Fir, Douglas 6.0-7.0
    Hemlock 5.0-6.0
    Hydrangea, blue-flowered 4.0-5.0
    Hydrangea, pink-flowered 6.0-7.0
    Juniper 5.0-6.0
    Laurel, mountain 4.5-6.0
    Lemon 6.0-7.5
    Lilac 6.0-7.5
    Maple, sugar 6.0-7.5
    Oak, white 5.0-6.5
    Orange 6.0-7.5
    Peach 6.0-7.0
    Pear 6.0-7.5
    Pecan 6.4-8.0
    Pine, red 5.0-6.0
    Pine, white 4.5-6.0
    Plum 6.0-8.0
    Raspberry, red 5.5-7.0
    Rhododendron 4.5-6.0
    Spruce 5.0-6.0
    Walnut, black 6.0-8.0
    Willow 6.0-8.0
  • Flowers
    Alyssum 6.0-7.5
    Aster, New England 6.0-8.0
    Baby’s breath 6.0-7.0
    Bachelor’s button 6.0-7.5
    Bee balm 6.0-7.5
    Begonia 5.5-7.0
    Black-eyed Susan 5.5-7.0
    Bleeding heart 6.0-7.5
    Canna 6.0-8.0
    Carnation 6.0-7.0
    Chrysanthemum 6.0-7.5
    Clematis 5.5-7.0
    Coleus 6.0-7.0
    Coneflower, purple 5.0-7.5
    Cosmos 5.0-8.0
    Crocus 6.0-8.0
    Daffodil 6.0-6.5
    Dahlia 6.0-7.5
    Daisy, Shasta 6.0-8.0
    Daylily 6.0-8.0
    Delphinium 6.0-7.5
    Foxglove 6.0-7.5
    Geranium 6.0-8.0
    Gladiolus 5.0-7.0
    Hibiscus 6.0-8.0
    Hollyhock 6.0-8.0
    Hyacinth 6.5-7.5

As you can see, some plants have a much wider range of tolerance than others and will thrive pretty much anywhere. Where as others are very specific about what soil they prefer. PH testing kits aren’t too expensive and you can even buy electronic ones on ebay.

If you have a plant that isn’t surviving too well in your garden, check out the PH level of the soil and see if the area around the plant may need to be treated to get your plant back on track.