Understanding Soil pH
Soil pH is a measure of how acidic or alkaline your soil is. It plays a crucial role in plant health by affecting how easily plants can absorb nutrients from the soil. Even when soil contains the right nutrients, an unsuitable pH level can prevent plants from using them effectively.
Understanding soil pH allows gardeners to make informed decisions about soil care, fertilising, and plant selection, helping to create the best possible growing conditions.
What Is Soil pH?
Soil pH is measured on a scale from 0 to 14:
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Below 7.0 – Acidic soil
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7.0 – Neutral soil
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Above 7.0 – Alkaline soil
Most garden plants grow best in soil that is slightly acidic to neutral, typically between pH 6.0 and 7.0, though some plants prefer more acidic or alkaline conditions.
Why Soil pH Matters for Plant Growth
Soil pH directly affects nutrient availability. When pH levels are outside a plant’s preferred range:
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Nutrients may become locked in the soil
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Roots may struggle to absorb essential minerals
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Plant growth can slow or weaken
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Leaves may yellow or show signs of deficiency
Correct soil pH helps plants absorb nutrients more efficiently, leading to stronger growth, healthier foliage, and improved yields.
Common Soil pH Ranges and What They Mean
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pH 3.5–5.5 (Strongly acidic): Suitable for acid-loving plants such as blueberries and azaleas
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pH 5.5–6.5 (Mildly acidic): Ideal for many vegetables, flowers, and lawns
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pH 6.5–7.5 (Neutral to mildly alkaline): Suitable for most garden plants
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pH 7.5–9.0 (Alkaline): Preferred by certain plants but may limit nutrient uptake for others
Knowing your soil’s pH helps you choose the right plants or adjust the soil to better suit existing ones.
How to Test Soil pH at Home
Soil pH can be tested easily at home using soil pH test strips. These provide a quick, colour-based reading that indicates whether soil is acidic, neutral, or alkaline.
Regular testing is useful:
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Before planting new areas
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When plants show signs of poor growth
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After applying fertilisers or soil treatments
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To monitor soil changes over time
For reliable results, always follow the test instructions carefully and test soil from below the surface.
How Often Should Soil pH Be Tested?
For most gardens, testing soil once or twice per year is sufficient. Additional testing may be helpful when adjusting soil pH or if plant health issues appear unexpectedly.
Understanding Your Results
Once you know your soil pH:
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Compare it to the preferred range for your plants
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Decide whether soil adjustments are needed
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Monitor changes after applying treatments
Testing both before and after making changes helps ensure soil conditions are moving in the right direction.
