After the arctic blast most of southwest Missouri got during January lots of homeowners will have extra wood ash this year.

If used sparingly, wood ashes left behind after burning wood for winter heat (in wood stoves, furnaces, and fireplaces) can benefit plants and gardens.

“Wood ashes have about one percent phosphate and less than 10 percent potassium, but no nitrogen. They also contain about 25 percent calcium carbonate, a common liming material,” said Patrick Byers, horticulture specialist, University of Missouri Extension.

Because wood ash has a fine particle size, it reacts rapidly and blends completely into the soil. Although small amounts of nutrients are applied with wood ash, the main effect is that of a liming agent.

“Gardeners often question the value and safety of using wood ashes in the lawn, gardens and flower beds. Yes, you may use them, but use them sparingly. Adding large amounts can do more harm than good,” said Byers.

It is also important when applying ashes to spread them evenly and avoid dumping them in one area. It is also a good idea to know your soil pH before adding the ashes (get a soil test).

Soils that are slightly acidic (pH 6.0 to 6.5), should not be harmed if 30 pounds of ashes per 1,000 square feet of garden area are applied.

Byers also recommends working ashes into the upper six inches of the soil.

“If your soil pH is 7.0 or higher, find another way of disposing of the ashes,” said Byers.

According to Byers, it is also important to never apply wood ash to acid loving plants like potatoes, rhododendrons, azaleas or blueberries.

For more information on fertilizer, contact the nearest University of Missouri Extension Center and request G6955, “Improving Lawn and Landscape Soils,” or MP733, “Lawn and Garden Soil Test Interpretations and Fertilizer Recommendation Guide.”

University of Missouri Extension programs focus on the high-priority needs of Missourians. Each county extension center, with oversight by locally elected and appointed citizens, is your local link to practical education on almost anything.