Should you use BBQ ash in garden soil? We separate fact from myth

Summer barbecue season brings with it a question: can I use BBQ ash in garden soil? You’ve chosen the best bbq, used it, and now you're wondering what to do with all that ash.

You’ve probably heard that wood ash is beneficial to your garden soil and plants, but is that really true? And if so, how should you be using it – sprinkled on your flowerbeds, or mixed into your compost? We investigate the claims about the benefits of BBQ ash in your backyard.

Is BBQ ash good for plants?

Unfortunately, there is no evidence that barbecue ash is any good as fertilizer for your plants. Wood ash can be beneficial, because, depending on the age and type of wood burned (the younger the better), wood ash contains decent amounts of potassium, which is a valuable nutrient for flowering and fruiting plants. If you have a wood burner, fire pit, or similar that uses real wood, then using up the ash as a fertilizer is not a bad idea, unless you have alkaline soil. 

Barbecues use charcoal briquettes, typically with added lighting fluid. Charcoal briquettes are not a good source of nutrients for your plants, while the chemical residue from the lighting fluid can actually be harmful to your plants. For the same reasons, barbecue ash shouldn’t go onto your compost. Instead, place it into your general waste bin, after it’s cooled down. You can learn how to compost in our guide.

Is BBQ ash good for regulating soil pH?

Adding any type of ash to your soil will make it more alkaline. This can be useful if you have very acidic soil in your garden and need to make it more alkaline, for example to grow vegetables, most of which prefer a pH level of 6.5. However, you’ll need to do careful soil testing to make sure you don’t make your soil too alkaline, which will harm your plants. Again, wood ash is the appropriate medium here, not BBQ ash, which you don’t want near edible crops.

Consumer horticulture expert and Associate Professor at Ohio State University Eric Barrett told Penn Live that ‘you gotta be careful’ with ashes: ‘First, did you burn anything else besides wood? Second, wood ashes raise soil pH. Do you really need to raise the pH? Base your need for it on a soil test.’ Learn more in our guide to soil types. 

If you have bought lump charcoal with no additives and not briquettes, you can add some of the BBQ ash to your compost – just be careful not to do this too often. Also note that some crops, notably raspberries, need acidic soil, so avoid alkalizing them with ash.