Is Your Compost Killing You
One of the comments that always strikes fear into our hearts at GardenAdvice is when a member or viewer says:
“I’ve just bought some bulk compost or soil improver to grow vegetables in my garden.”
On the surface, it sounds like a positive step. But for us, alarm bells immediately ring. Why? Because all too often, these products come with hidden dangers: high or low pH levels, poor soil structure, and—worst of all—concentrated heavy metals.
The Problem with “Eco-Friendly” Compost
Many of these products are marketed as eco-friendly compost, soil improver, or topsoil. They’re often black in colour, with little structure, and sometimes have a pH as low as 4. The glossy “green” label hides an uncomfortable truth:
- Waste is expensive – Proper disposal costs companies money. But if waste can be rebranded as compost, it becomes profitable.
- The peat backlash – With peat falling out of favour, “composted waste” slots neatly into the market as a sustainable alternative—regardless of its quality.
- Attractive margins – Selling waste as compost is the perfect business model financially, but often not horticulturally.
What Our Testing Shows
At GardenAdvice, we often test compost and soil products for our members and clients—sometimes before use, but often after problems appear. The results are consistent and worrying:
- Destructured compost or soil – Instead of building fertility, the soil or compost loses structure and life.
- Low pH – We’ve seen composts with pH values as low as 4, far from ideal for most vegetables or indeed most other plants.
- Heavy metals – Root crops like carrots and potatoes store energy in tubers etc they concentrate energy into for example carrots and potatoes, they also store heavy concentrate metals from contaminated soils and composts, which then end up on
- Full fungal spores – leading to mildew and other fungal diseases.
- Excess nitrates – Some mixes are overloaded with nitrogen, producing lush growth but creating health risks when consumed in high amounts.
- No worms – Perhaps the biggest red flag: worms won’t touch it. If soil life is absent after using eco compost or soil improver, something is badly wrong.
Why It Matters
Most gardeners blame themselves when seedlings collapse or mildew runs riot. They assume it’s inexperience or poor technique. In reality, the culprit is often poor-quality compost or similar products
And the danger isn’t just to your plants. Eating vegetables that have concentrated heavy metals or nitrates can pose genuine risks to your health. That’s why “Is your compost killing you?” isn’t just a headline—it’s a real question.
Regulations: Weak and Rarely Enforced
There are regulations around composting, but they are sketchy at best and rarely enforced. Even long-trusted composts carrying the John Innes named compost are being watered down, with recipes altered by large manufacturers chasing profits. The result is a marketplace full of unreliable, sometimes unsafe products.
The GardenAdvice Approach
We don’t want to leave our members guessing. This winter, the GardenAdvice Team has launched a major programme of testing a wide range of composts. Over the coming months, we’ll be publishing live results to help gardeners make informed choices.
Our aim is simple:
- Identify safe, reliable products
- Recommend composts we’ve tested
- Support members with science-based advice
As soil science advances, and as the industry faces pressure to improve, we hope regulations and standards will catch up. But until then, our best defence as gardeners is awareness and careful choice.
If you are not sure about your compost or soil improver just ask us Click Here
Your compost should nurture life, not threaten it. If your soil is lifeless, acidic, or contaminated, the problem isn’t you or gardening skill—it’s often the product. By testing, sharing results, and guiding our members, GardenAdvice is here to make sure your compost keeps you—and your garden—healthy.
Learn more about GardenAdvice gardening courses and other services Click Here
Making Your Own Compost – The Safer Alternative
One of the best ways to avoid the risks of poor-quality compost is to make your own. By composting garden waste, kitchen peelings, and other natural materials, you control what goes into your compost and what eventually goes onto your crops.
Benefits of home composting:
- Full control – You decide the ingredients, ensuring no contaminants.
- Healthy soil life – Properly made compost supports worms, fungi, and beneficial bacteria.
- Cost savings – It’s free fertiliser and soil improver from waste you already produce.
- Sustainability – Reduces reliance on industrial waste products disguised as “eco-compost.”
At GardenAdvice, we provide step-by-step guides and advice to help you succeed with composting at home:
With the right mix of green (nitrogen-rich) and brown (carbon-rich) materials, plus patience, you’ll create a safe, fertile compost that keeps both your plants and your family healthy.
