Wood Ash

There is a quick and easy way to add some minerals, especially Potassium to your garden while also deterring slugs and snails from your favourite plants. It’s Wood Ash.

Wood ash is full of nutrients including Calcium, Zinc, Magnesium and Copper and especially Phosphorus and Potassium. It will, most likely, also contain burned staples, pins, nails and bits if wire. Unless they’ll be a safety hazard, bury them in your garden too. The fire will have oxidised a lot of the metal and made it easier to break down in the soil, providing iron eventually once it’s been processed by the various chemical and biological systems in the soil. Wood ash also contains a lot of little or not so little fragments of charcoal. These will benefit your garden immensely as when soil bacteria, fungi and microbes have colonised it, you have small amounts of an equivalent to biochar

With wood ash, ‘lightly‘ is the guiding principle. It is pretty alkaline (they use it to make lye for soap making and that stuff’s like caustic soda) so use sparingly and make sure you don’t breathe it or get it in your eyes – mask and glasses are the go, please, if you want to distribute more than a handful.

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A bit about pH

pH is the measure of acidity/alkalinity. It is important to plants because it affects their ability to uptake certain nutrients. It also affects and is affected by the microbes and fungi that are active in the plant’s root zone and which contribute to plant nutrition.

pH is measured on a scale from acid to alkaline. It is a measure of the number of hydrogen h+ ions in the measured substance (usually water). A low pH is acidic and is below 7 on the scale. Neutral is 7 and alkaline is anything over 7.

A bit about Potassium

Potassium is necessary for flower production, fruit growth. It is helpful when you are growing plants for their flower heads and associated parts. These are plants like Broccoli and Cauliflowers.

While talking about chemical systems, I should note that if you’re adding wood ash to your garden just for the Potassium, there are other options that won’t cause a drastic change in pH.

Comfrey leaves, Nettles and Banana peels are excellent sources of Potassium, in a ready for bacteria to digest, organic, form. Adding these to the soil around your plants will help build Potassium levels without negatively affecting the pH. I usually blend them, soak overnight and pour the strained liquid around the plants that need it. The remaining slide goes out on the garden too. Check out our odourless compost tea press for a simple DIY way to make Comfrey or Nettle tea.

Also, there is a strong relationship between the Calcium in your soils and the ability of plants to take up Potassium. Soils high in Calcium can prevent plants from taking up Potassium, so if you live on high Calcium soil, it may block your efforts to give extra Potassium to your plants. Making your soil more acidic by adding Humic Acid from your local hydro shop (a quick, temporary solution) or building levels of humic acid and other organic acids in your soil (the long term, preferable solution) can lower your pH enough to help your plants

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What’s actually in wood ash depends on what was burnt but it does tend to be on the alkaline side, so don’t use too much and don’t use anything burned that contains known toxic materials like plastic or permapine.

A slight dusting is all that’s required. It’s powdery, alkaline, nature is loathed by slugs and snails and will work until the rain or your watering washes it away from the leaves and onto your soil where it will continue to do good by feeding your plants.

I usually keep some spare for the yearly attack of the Pear Slugs. It works a treat on those buggers. Once again, just a dusting, don’t throw handfuls at them.

We also use Wood Ash sparingly in the chicken run and coop to deter mites and parasites. Once again, a light dusting is all that’s needed.