A soil’s pH is one of the key determinants for how successfully certain plants will go. A soil with a low pH is acidic, while soil with a high pH is alkaline. Because plants have specific pH requirements, it is critical to know the pH of your soil in various locations of your garden. Indicator plants are a great way to see what type of pH your soil has (as well as to indicate the drainage of your soil, or whether the soil is nutrient-rich or depleted). Indicators of acidic soil include creeping buttercup, German chamomile, nettles, plantain, sheep’s sorrel, and sow thistle. There are many other indicators of a garden that is a low pH, but these are the ones I most frequently encounter in my garden, on the west side of the Cascades in Washington State. Particularly my nemesis, the aforementioned creeping buttercup (see pic below). GROWL.
To more formally test the pH of your soil, you may choose a variety of methods, from using a home pH kit (order one online) or a commercial test probe, to testing with boiled red cabbage water (this is a particularly fun method involving water that turns blue, green, purple or even hot pink depending on the soil introduced – great to do with kids!), or testing with vinegar and baking soda. Despite the variety of applicable pH tests, I’ve never had to explore pH testing in my garden. Ever.
Why? Because I live in the middle of a conifer forest, which means my soil is absolutely, undoubtedly, extremely acidic (especially considering we have two enormous Douglas Firs growing precisely in the middle of our permaculture project, littering all of the surrounding soil and berms with fir needles; each gust of wind or snowfall scattering the garden with fir detritis, the debris in winter helping to insulate and protect the soil, only to break down and leave the pH of the soil far below neutral (a neutral pH is around 7). If the presence of conifers and living in the Northwest didn’t already make our soil pH obvious, the indicator plants in our yard make the situation crystal clear. Our soil’s acidity has largely determined what we can or cannot grow in our garden.
Because we want our permaculture project to be permanent, natural, and low-maintenance, we mostly choose plants that love acidic soil. We have planted too many blueberry bushes to count, tea plants, wintergreen berries, kinnikinnick (a.k.a. bearberries), huckleberries, ajuga (as a ground cover), azalea, camelias, rhodies, rhubarb, parsley, pepper, tomatoes, and potatoes throughout the yard (post of planting for acidic soil coming soon). Any plants native to the Pacific Northwest or used in regional traditional remedies are plants that either grow in acidic soil, or are adaptable in a range of pH soil conditions. Plants that require particularly alkaline soil, or at least pH-neutral soil, we try to corral together in raised beds, or in our more traditional annual garden, which are areas where we focus our composting and alkalizing efforts. Most vegetables require at least pH neutral soil, with the exception of radishes. (Another post on my love for the radish and its benefits for the garden, as well as the plate, will also be forthcoming).
Composting is critical for your annual, alkaline or pH-nuetral-loving focus areas. The breakdown of most organic matter is pH neutral, so collecting food waste and other leaves and mulch and allowing them breakdown in the garden will move the soil to a neutral pH and away from both extremely acid or alkaline soil pH (YAY compost!). For alkalizing in particular, egg shells are highly alkalizing and wonderful for the garden – we even crush our egg shells up and put them in our watering container for watering indoor plants (they love it), before dumping the egg shells outdoors when the container becomes full.
Some of the more zealous may choose to purchase dolomite (a natural mineral) or quick lime (a caustic substance created by heating limestone) from gardening stores to till into the soil and help balance soil pH, but wood ash can be a readily available and helpful alternative. We heat our house with a wood stove as our main source of heat in winter, and the as wood burns, sulfur and nitrogen escape as gasses, leaving behind ash rich in potassium, magnesium, and calcium.
The application of the wood ash to the garden is easy and helpful. Every time I empty our woodstove, I either mix the wood ash into our compost pile, or apply the ash directly to the garden and rake the ash into the soil, making sure to get rid of any large clumps, as ash is high in salt, and concentrated clumps can break down and create an environment undesirable for most plants.
However, my favorite application of wood ash for soil alkalizing is actually directly onto the lawn. We do not use any chemicals on our lawn, and truth be told, we have very little of what could be considered “lawn,” on our property. Most of our existing grass grows wild and free in the field behind our house, or has been dug up for our permaculture berms and paths. Nevertheless, few patches of lawn I have preserved, I would prefer to be lush for handstands, summer naps, or picnics, vs. crowded with plants indicating the soil’s acidity. Acid soil also retains less water than more alkaline soil, meaning that neutralizing the soil your grass grows in can actually help the lawn retain moisture, reducing water needs and increasing the health and verdancy of the lawn.
To apply wood ash to the lawn, I simply pick a day when it is raining lightly, or when I know a storm looms on the horizon. I collect the ash in a pail, and take it outside to scatter over the creeping buttercups that are currently the primary indicators of my lawn’s acidic soil. I spread the ash evenly and thin – I can always choose to scatter more wood ash if necessary, but it is impossible to remove once the rain has worked the wood ash through the grass, and it has permeated the soil with its nutrients.
Additionally, wood ash can be applied directly around plants that require more alkaline soil. Again, ash should be applied minimally each time, and worked into the soil, raking it in gently, and breaking up any residual clumps. The ash should not be applied to seedlings, as the salt can be too intense for germinating or young plants, and the gardener needs to be sure that the wood ash is indeed the ash of wood, as opposed to the ash of painted or stained wood, pressure-treated boards, glues, tapes or plastics whose trace elements can be harmful for plant growth.
Enjoy playing with fire, and the subsequent benefits on your garden and lawn.