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Wednesday - September 28, 2011

From: Islesboro, ME
Region: Northeast
Topic: Soils
Title: Fireplace ash as soil amendment in Maine
Answered by: Anne Bossart

QUESTION:

It seems that the custom where we summer in Maine is to dispose of wood ash from the fireplace on the plants around the outside of the house. I think this is not a good idea. What is your opinion? I was going to put them in the middle of the gravel drive.

ANSWER:

Well, it really depends on how acidic your soil is and how much ash you have to get rid of.

Wood ash does have some nutrient value but it is made up of less than 10 percent potash, 1 percent phosphate and trace amounts of micro-nutrients such as iron, manganese, boron, copper and zinc. It contains absolutely no nitrogen and is about 25% calcium carbonate, which is an ingredient in garden lime.

So it increases the alkalinity of your soil ... which may or may not be a good thing. You really should only add lime (wood ash) to your soil if your pH is 5.5 or less (very acidic). Ideally, soil should be neutral (pH 7.0) and higher alkalinity can inhibit the uptake of some micro-nutrients.

Many gardeners in the north (Maine and Eastern Canada) where the bedrock is granitic and there is an abundance of pine and other conifer trees believe the soil is acidic and should be "limed" every fall. A walk in the woods will reveal many acid loving members of the ericaceous family such as

Andromeda polifolia (Bog rosemary)

Arctostaphylos uva-ursi (Kinnikinnick)

Gaylussacia dumosa (Dwarf huckleberry)

Gaultheria procumbens (Checkerberry)

Kalmia angustifolia (Sheep laurel)

Rhododendron canadense (Rhodora)

Vaccinium angustifolium (Late lowbush blueberry)

Vaccinium macrocarpon (Cranberry)

These are plants that define Maine, so don't alter your soil so much that they cannot thrive. Do a soil test and then amend as is appropriate.

I agree with you ... the driveway is probably a good place for them!