Soil Amendment: Using Wood Ash in Your Garden

We are elbows deep into a full-blown Spring cleaning at my house, literally! With tools and a paper bag in each one of my rubber-gloved hands, I stare into the very sooty mess of a well-used fireplace. I only hope that we are done with this unseasonably cold weather, so that I may finally close the damper, and harvest the remaining hardwood ash for the garden beds. The benefits of wood ash to plants, and its contributions in the replenishment of the soil, are nothing new to the well-tuned Gardener.  If you think about it, even Mother Nature replenishes itself with more vigor after a forest fire, right?

Why Add Wood Ash?

When amending your garden soil in the Spring, the purpose is to replenish nutrients lost during last year’s growing season, and over the winter. Besides using organic matter like compost and manures, have you considered using burned wood ash? Wood ash is beneficial for increasing soil ph. Depending on the hardness of the wood used; its ash will fall between 9 and 13 on the ph scale. For all us who have been out of school for a while, this places it on the alkalinic side, giving it properties similar to using a 0-1-3 fertilizer. Wood ash also contains a minimal reserve of phosphorous and potassium, but is also void of nitrogen; which also makes it comparable to adding lime to your garden.  A simple soil test can determine if your soil is acidic, and in need of the benefits from wood ash. As a rule of thumb, areas with high concentrations of rain (about 20 inches per year) tend to have acidic soil. On the contrary, if your soil is already at a 7.5 ph or greater, wood ash would not be beneficial.

 

How and Where to Apply

In either the early Spring or Fall, apply up to 20 pounds per 100 square feet, working it well into the soil to a depth of 6 inches in areas where you will be locating plants with acidic tendencies. You can lightly sprinkle the ash around your established plants, but avoid new seedlings and sowed seeds as the concentration of salt is harmful to young plants. Keep in mind, if working it into your soil; allow 2 weeks to pass before setting seeds or transplants.

A few examples of plants that benefit from wood ash:

Exceptional health and growth of tomatoes, cabbage, asparagus, peas and beans especially. Likewise, root vegetables such as carrots and parsnips also benefit by the ash’s ability to repel carrot flies and root maggots. Lightly apply to any garden flowers and yard beds containing sunflowers, carnations, daffodils, asters, poppy, clematis, spirea, boxwoods and yews. Additionally, any fruit trees on your property can use a light sprinkling.

A ½ to 1 pound of wood ash per year is recommended for your shrubs or roses. Additionally, if your lawn is lacking lightly spread on the grass and gently rake in, applying no more than 10-15 pounds per 1,000 square feet.

But, always remember…Never leave lumps or piles of wood ash on or near your vegetation, as the concentration of salt from the ash is toxic to plants!

Plants to avoid:

Make sure you check the ph numbers of your plants if you are unsure whether or not to apply, but junipers, pines, firs or spruces, holly, azaleas, rhododendrons, blueberries, calla lilies, delphinium, crocus, camellias, phlox and ivy should be avoided.

It is also good to know to avoid your potato patches, in which wood ash will encourage the fungus that contributes to potato scab.

 

Pests, Composting and Ponds

Wood ash can be used also as a deterrent to surface feeding pests. Especially effecting slugs and snails as it draws water from their bodies, killing them.

If using wood ash in your compost pile, a light sprinkling after adding organic matter such as dried leaves, pine needles, or fruit waste will help the balance. Additionally, wood ash loses its benefits once it gets wet, so keep your supply covered or in a dry area.

Have some extra wood ash, even after adding it to your garden? If you are lucky enough to have a garden or fishing pond, go ahead and add one tablespoon to every 1,000 gallons of water. The potassium in the ash slows algae growth and aids the aquatic plant life.

Now, you if you are going to be hungrily looking at all that ash produced by the outdoor bonfires this Summer, go ahead and get sooty! But, you may want to avoid the ash that was left over after Uncle Ned threw his red Solo cups in the fire…

 

Cheers!