Wood Ashes in the Garden: Good or Bad?

One of the things I love the most about cooler weather is the nice cozy fires that my husband builds in our fireplace and outdoor fire pit. Whether it’s because he is a Sagittarius (one of the fire signs of the zodiac) or just because he grew up in a campfire loving family, Tom starts building fires as soon as the temperatures begin to fall.

Needless to say, we end up with a LOT of wood ashes. The first time I cleaned out our fireplace (over ten years ago now) I piled huge buckets full of ashes into our compost pile. It just seemed somehow logical to me, putting decomposed wood back into the earth. Tom, my green-gardening guru hubby, just shook his head. Then he told me to get a shovel and he helped me dig them all back out and put them in a metal container so we could better control their use in our landscape.

I wasn’t WRONG about the nutritional value of wood ashes. The truth is that wood ashes contain most of the 13 essential nutrients that soil must supply for plant growth. The secret is just to make sure that you utilize those nutrients ONLY as needed.

When applied directly to garden soil, wood ashes will raise the pH level. This is great if the pH level of your soil is low. Not so great if the pH level of your soil is already high. In fact, over applying wood ash can cause serious imbalances in your soil.

The pH value is a measure of a soils acidity or alkalinity and directly affects the ability of plants to utilize the nutrients available to them. The pH scale ranges from 0 to 14, with 7 as neutral. Numbers less than 7 indicate acidity while numbers greater than 7 indicate alkalinity.

So how do you determine the pH value of your soil? You get your soil tested.  Getting your soil tested is an excellent way to help minimize the use of chemicals in your yard. Knowing what your yard needs allows you add only what is necessary, eliminating the possiblity of harming your yard or causing excess nutrients to find their way into our waterways.

If the pH level of your soil is low, then adding wood ash may be beneficial. Again, this depends on what you want to grow. Wood ash is beneficial to most garden plants except acid-loving plants such as blueberries, rhododendrons and azaleas.

Here are a few more facts about wood ashes, I found from searching usasearch.gov:

The value of wood ash depends on the type of wood you burn. Harwood ash has a higher percentage of nutrients than ash from softwoods.

Lawns that need lime and potassium can also benefit from wood ash but you should apply no more than 10 to 15 pounds of ash per 1,000 square feet of lawn and only every couple of years.

Wood ash is alkaline, which means you should use precautions when handling it.

• Wear eye protection, gloves and a dust mask.
• Do not scatter ashes in the wind.
• Do not use ash from burning trash, cardboard, coal or pressure-treated, painted or stained wood. These materials can contain potentially harmful substances. For example, the glue in cardboard boxes and paper bags contains boron, an element that can inhibit plant growth at excessive levels.
• Never leave wood ash in lumps or piles. If it is concentrated in one place, excessive salt from the ash can leach into the soil and create a harmful environment for plants.
• Do not apply ash at time of seeding. Ash contains too many salts for seedlings.

Source: Wood Ashes Can Benefit Gardens and Lawns

Eco-friendly gardens are "no-sweat"

Every summer at about this time, I sit back, relax with an ice-cold drink, and think about some of the added benefits of eco-friendly gardening. In many ways, eco-friendly landscapes require less work, meaning that I can have more of a “no-sweat” summer than some of my friends and neighbors with more labor-intensive landscapes.

Below are some great reasons to think about turning your traditional landscape into an eco-friendly, “no-sweat” one:

1. Eco-friendly gardeners work WITH Mother Nature, not against her: choosing plants that fit the site means plants are better adapted to survive with minimal care, which means Mother Nature takes care of the plants, not you.
2. Eco-friendly gardeners leave part of their landscape natural: Why tear out existing, native species only to replace them with more labor-intensive exotics? Native plants, which are present on a property, will require less work and will provide an immediate benefit to local wildlifespan>
3. Eco-friendly gardeners plant trees with energy conservation in mind: Shade trees can significantly reduce air temperatures in and outdoors in the summer, as trees intercept and absorb the sun’s heat while transpiring cooling moisture into the air.
4. Eco-friendly gardeners incorporate drought tolerant species, which means less work watering. Drought tolerant trees drought tolerant perennials
5. Eco-friendly gardeners group plants by their care requirements : plants that do require extra water or fertilizer are all in one place, rather than scattered throughout the property.
6. Eco friendly gardeners include beneficial plants: beneficial plants attract bugs and birds that help cut down on insect pest populations, eliminating the need to apply pesticides.
7. Eco friendly gardeners have their soil tested to determine the right mix of fertilizer for their lawn rather than applying fertilizers that aren’t needed.
8. Eco-friendly gardeners identify weeds and pests rather than spending time indiscriminately killing them all. Some bugs are good bugs. And a weed-free lawn is not necessarily a healthy one.
9. Eco friendly gardeners replace lawn with ground covers : Most ground covers need little or no maintenance once they’re established.
10. Eco friendly gardeners use plenty of mulch : adding mulch helps cut down on both weeding and watering
11. If they do have lawn, eco-friendly gardeners mow less oftenMowing grass to the proper height is the single-most important thing you can do to improve the health of your lawn.
12. Eco-friendly gardeners don’t rake their grass clippings : Leaving grass where it falls adds nutrients back to the soil. However, be sure to sweep up your sidewalk, driveway or street so clippings don't pollute nearby lakes or streams.
13. Eco-friendly gardeners create compost : why lug bags of trash to the curb and bags of purchased soil enhancers to your landscape? Composting your yard and kitchen scraps saves time and money.
14. Eco-friendly gardeners water less: Plants should be watered only when they begin to droop and in the early morning hours before 10 a.m. Grasses naturally grow slower in the summer, so brown grass usually means your lawn is just dormant, not dead.
15. Eco-friendly gardeners use hardscapes creatively: Hardscapes, the landscaper’s term for paving and built features in a garden (think patios and walkways) reduce garden work and extend your home’s living space. Using permeable surfaces also allows water to percolate into the ground, rather than

Get your soil tested

If you are looking for something proactive to do to prepare for your spring time landscaping, now is a good time to get your soil tested. Testing your soil now gives you plenty of time to make any adjustments necessary to get your landscape in prime planting condition.

A soil test can provide a great deal of information about the pH and nutrients of your soil. Knowing what is already in your soil will allow you to apply the proper amount of lime and fertilizer, minimizing the water polluting nutrient runoff which can be caused by overfertilization.

Scott Reiter, an Extension agent with the Prince George County office of Virginia Cooperative Extension, provides these steps for getting a good soil sample:

First, you need to select the right tools for the job. A soil probe is the best tool for taking a sample because it is fast and collects the soil evenly from top to bottom. A soil probe is essentially a sharpened pipe with a handle on top. These probes can be purchased at some farm supply and hardware stores. For those of you that only need to take 1 or 2 samples a garden trowel or small shovel will work just fine. Next, find a clean plastic bucket to collect your soil in. Do not use galvanized buckets or tools because the zinc in the coating will affect your test results. 

I usually recommend that at least 10 subsamples be collected from the area you are testing. The more subsamples you collect from an area the more accurate your results will be. In lawns, landscape beds, pastures, or hay fields collect soil to a 4-6 inch depth. This is where most plant roots are found and soil amendments are easily added to this depth. Vegetable gardens and crop fields should be sampled to the tilling or plowing depth. Be sure you sample the same depth throughout the entire area. Once you have collected the soil, thoroughly mix it and remove any large roots or gravel. Fill your sample box with the mixed soil and you are done with this sample. 

You may need to take multiple samples around your home or farm. The vegetable garden, front lawn, flower beds, or newly cleared areas are examples of separate sampling areas. If you have an area where plants do not grow well, sample that area separately too. 

Once you have completed taking your samples you are now ready to submit them to a reliable laboratory. Virginia Tech has a soil testing laboratory for use by citizens of the Commonwealth. Homeowners can submit samples for a $7 per sample fee. There are also private soil testing laboratories that charge comparable fees. You should receive your soil test results 1-2 weeks after mailing them. I caution people with relying on the do-it-yourself testing kits. There is more chance for error when running the test yourself and relying on color matching charts to determine nutrient levels. A soil testing laboratory uses a standard procedure and runs test samples to make sure the results are accurate.

For more information about soil testing, read:
Preparing soil in winter for a successful spring
Soil Sampling for the Home Gardener