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How to Make Soil Acidic
- Little Loads
- 9 hours ago
- 3 min read
If your azaleas aren't blooming or your blueberries look lacklustre, your soil's pH might be the culprit. Many popular garden plants thrive in acidic conditions, but Perth's naturally sandy and often alkaline soils can make this tricky. The good news is that adjusting your soil pH is straightforward when you know what you're doing.
What Is Soil pH?
Soil pH measures how acidic or alkaline your soil is, on a scale from 0 to 14. A pH of 7.0 is neutral, anything below is acidic, and anything above is alkaline. Most plants prefer slightly acidic to neutral soil (around 6.0–7.0), but acid-loving plants need a pH between 5.0 and 6.0 to properly absorb nutrients like iron, zinc, and manganese.
Perth's coastal and sandy soils often lean alkaline, which can lock up these essential nutrients and leave your plants struggling, even with regular feeding and watering.
Which Plants Need Acidic Soil?
Before you start adjusting pH levels, it's worth knowing which plants actually benefit from acidic conditions. Common acid-loving plants include the following.
Flowering Plants
Azaleas and rhododendrons
Camellias
Hydrangeas (for blue blooms)
Gardenias
Magnolias
Edibles
Blueberries
Cranberries
Potatoes
Rhubarb
Trees & Shrubs
Most evergreens and conifers
Hollies
Heathers
If you're growing these plants in Perth's naturally alkaline soil, you'll likely need to make some adjustments.
Testing Your Soil First
Never guess your soil's pH. Always test it first. You can pick up an affordable soil test kit from your local garden centre or hardware store. Simply collect samples from different areas of your garden, follow the kit instructions, and compare the results to the pH chart provided.
Testing takes the guesswork out of soil amendments and prevents you from over-correcting, which can cause more harm than good.
Natural Ways to Acidify Your Soil
Sulphur-Based Products
Elemental sulphur is one of the most effective and long-lasting ways to lower soil pH. It works slowly as soil bacteria convert it into sulphuric acid, gradually reducing alkalinity. For faster results, you can use iron sulphate or aluminium sulphate, though these work best for smaller garden beds or container plants.
Application rates depend on your soil type:
Sandy soil: 150–200g per square metre
Loam: 200–280g per square metre
Clay: 280–450g per square metre
Apply evenly across your garden bed, water it in well, and retest after 6–8 weeks.
Organic Matter & Compost
Adding organic matter like our soil conditioner or well-aged compost can help lower pH over time while improving soil structure and moisture retention. Organic materials break down and release mild acids, creating a more favourable environment for acid-loving plants.
Our Soil Conditioner is NASAA Certified Organic and specially formulated to improve Perth's sandy soils. Mix it thoroughly with your existing soil rather than planting directly into it.
Coffee Grounds & Organic Mulches
Used coffee grounds contain natural acids and can be worked into the soil or used as a light mulch. While they won't dramatically shift pH on their own, they're a useful supplement when combined with other acidifying methods.
Similarly, organic mulches like pine needles or composted bark gradually release acids as they break down, helping maintain slightly acidic conditions.
What Doesn't Work to Acidify Soil
Despite what you might read online, vinegar and lemon juice aren't reliable soil acidifiers. They provide only temporary pH changes and can harm beneficial soil microbes. Stick with proven methods like sulphur products and quality organic matter.
Maintaining Acidic Soil Long-Term
Soil pH doesn't stay constant. Leaching from rainfall, fertiliser use, and natural processes can shift pH over time. Retest your soil every 2–3 years and reapply acidifiers as needed to keep your acid-loving plants happy.
For container plants or small garden beds, consider using a quality potting mix designed for acid-loving plants. Our potting mix offers excellent moisture retention and is suitable for a wide range of plants.
At Little Loads, we stock everything you need to improve your soil, from our NASAA Certified Organic Soil Conditioner to specialist mixes designed for Perth's unique conditions. If you’re not sure how much you need, use our online calculator or contact us for assistance.
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