Science Smarts: Green up your thumbs with this at-home soil pH test

By Patty Rooks on May 31, 2025.

Oh my, we are getting into one of my favourite times of the year – gardening season! Based on advice from my favourite farmer, I always wait to put my plants out after the May long weekend, so I think it is time to get out there and get planting. Before I start though, I need to prepare the soil as I want the most beautiful plants possible.

As a result, this has made me wonder if I need to take a close look at my soil pH. It is important to know the pH of your soil as different plants like alkaline soil and some do not. Of course, I could pay for a lab to test my soil, but I thought perhaps I could do some testing first. Let’s get started!

*Remember to ask an adult before doing this experiment.

Materials

– Sample of soil to test (at least one cup full)

– Head of red cabbage

– Kettle

– Water

– Heat proof bowl

– Cutting board

– Strainer or sieve

– Two white dishes

– Measuring cup

– Spoon

– Jar

– Medicine dropper or pipette

– Adult helper

Procedure

1. The first thing you need to do is to make an indicator. A simple indicator to test for pH can be simply made with red cabbage.

2. Have an adult cup the head of red cabbage into fine slices.

3. Place the sliced cabbage in the bowl.

4. Fill the kettle full of water and allow it to boil.

5. Ask an adult to pour the boiling water over the sliced red cabbage.

6. Make sure the water covers the cabbage and allow it to sit until it is cool for at least 20 minutes.

7. The water should be a brilliant purple colour, this is how you know it is ready.

8. Strain the cabbage from the purple water into the jar.

9. Set the indicator aside for now.

10. Place a spoonful of soil on the white plate.

11. Fill the medicine dropper with the indicator.

12. One drop at a time, put the indicator on the soil sample.

13. Be careful how much you add, you do not want it to be completely saturated, but you do want enough of the indicator on the plate so you can actually see a colour change.

14. Swirl the plate around.

15. Wait at least one minute.

16. Observe what you see.

17. Repeat again on the other plate so you can be sure of your results.

What is going on?

You should see the cabbage juice indicator change colour or remain the same perhaps; it will depend on your soil sample. If the cabbage juice turns red, the soil is acidic or in the pH range of 0.0 – 6.9. When the cabbage juice is blue or green the soil is basic or a pH of about 8.0 -14.0. A purple or bluish purple colour indicates that the soil is neutral or a pH of 7.0. The pH of soil is very important for different plants. Most plants do well in a pH of six to seven. Potatoes for example like a pH of about 5.0 – 6.5; carrots 5.5 – 7.0; lettuce 6.0 – 7.0. You can add some things to the soil in order to change the pH to better suit the plants that you want to grow. Make sure you talk to the professional at your local garden store for help

Calling all educators! Booking for our Hands on Learning Kits for the 2025-26 school year will open up June 1 – you can book for the entire year if you have your planning ready. Email your requests ASAP as it is first come first served. As well, keep reading here as there will an exciting announcement on a new hands-on offering for the junior high classroom thanks to the generous support of TC Energy!

Patty Rooks, senior scientific consultant PRAXIS, “Connecting Science To The Community.” Praxis has moved! We are very fortunate to be located in the Community Futures Entre Corp Building at #202 556 Fourth St. SE, Medicine Hat, Alberta, T1A 0K8. For all your science needs, please email praxis@praxismh.ca.

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