Soil pH is one of the most common silent reasons plants struggle — even when you water and feed them correctly.
Soil pH is a measure of how acidic or alkaline your soil is on a scale from 0 to 14:
- pH 7 = neutral
- below 7 = acidic
- above 7 = alkaline
Most plants have a pH range where they can absorb nutrients properly. Outside that range, nutrients can become harder to access — so plants look weak, yellow, or stunted even if the soil contains nutrients. RHS notes most plants grow best within a particular pH range and it’s useful to know your soil pH.
Why pH matters
pH affects:
- nutrient availability (how easily roots can take up nutrients)
- soil biology (microbes, earthworms, breakdown of organic matter)
which plants naturally thrive
RHS also highlights around pH 6.5 as a useful general purpose level for many garden plants.
Common pH patterns
Chalky soils tend to be more alkaline and can be difficult/impossible to truly acidify long-term; better to choose plants that suit alkaline conditions.
Some gardens sit nearer neutral or slightly acidic and support a wide range of plants well.
How to test soil pH
RHS says testing kits are easy to use and widely available.
Best practice:
Take small samples from a few spots
Mix each area sample separately
Test and record results
Use results to choose plants and plan amendments
What to do if your soil is too acidic or too alkaline
If soil is too acidic
Some plants love this, but many don’t.
You can sometimes raise pH gradually depending on soil type and what you’re trying to grow.
If soil is too alkaline
RHS notes very chalky soils cannot realistically be acidified and you’re better choosing plants that thrive in alkaline conditions.
Quick pH troubleshooting signs
- Yellowing leaves with green veins (can be pH-linked nutrient lockout)
- Poor flowering / weak growth
- Repeated failures in the same bed while other areas do fine
If you want, we can assess: plant type + symptoms + your soil type + photos.