What to Do with Wood Ash from Woodstoves and Fireplaces

What to Do with Wood Ash from Wood­stoves and Fireplaces

From one of my Per­ma­cul­ture Con­sul­ta­tion clients

Dear Cathe’,

It was great to visit with you yes­ter­day. I have a ques­tion. We have been col­lect­ing ashes from Kathleen’s fire­place in a large trash­can in the garage. I was won­der­ing about using them in the green­house or gar­den. Do you know of any uses for wood ash? What do you think about putting ash in the compost?

Love, Kather­ine

Hi, Kather­ine,

Take wood ash from wood stove or fire­place in a metal bucket. Never store in plas­tic until ash is absolutely cool. This way you avoid burn­ing down buildings.

Use only high qual­ity wood ash. No ashes from BBQ grills, card­board, ply­wood, painted, or pres­sure treated wood. Hard­wood ash (oak) is supe­rior to soft wood (pine) ash.

Three Caveats
1. DO NOT USE ASH IF YOUR SOIL HAS AN ALKALINE pH of 7.5 or higher. It will make the soil too alka­line or salty. Alka­line soils are found in low rain­fall areas in the West. Use wood ash only in loca­tions where soils are acidic, like for­est soils and moun­tain soils, or places where there is ade­quate rain­fall in the warm sea­son .…not in alka­line soils like the desert. If in doubt, con­tact your local Mas­ter Gar­den­ers http://www.ahs.org/master_gardeners/

If you have been farm­ing or gar­den­ing with chem­i­cals, check your soil pH. Most chem­i­cals increase the pH and will even­tu­ally salt the soil

On the pH scale, 7 is neu­tral like pure water, below 7 is acidic with 1 being the most acidic like bat­tery acid; and above 7 is alka­line with 14 being the most alka­line like liq­uid drain cleaner. Nor­mal gar­den soil is typ­i­cally 5.5 to 7.5 pH. Wood ash is typ­i­cally 10.4 pH

2. Don’t use wood ash near these and other acid lovers: aza­leas, rhodo­den­drons, blue­ber­ries, mums, marigolds, moun­tain lau­rel, oak, pecan, and sweet potato

pla 3. Sprin­kle wood ash before plants emerge, in win­ter or very early spring. Don’t plant seeds or seedlings until at least two weeks after ash has been applied, or wait until new plants are a few weeks old to spread it. The smaller they are, the more dra­mat­i­cally plants may react to the sud­den increase in pH.

Wood ash has the same com­po­si­tion as lime­stone. Use it where you would use lime. If you put a pile of wood ash out­side, and it rains, it will turn to limestone.

The secret to using wood ash is to SPRINKLE IT or DUST IT.

Use wood ashes to:

1. Spread finely on the soil on your prop­erty. Use a large cof­fee can or a box with nail holes punched into the bot­tom. Spread so it looks like fine baby pow­der on the soil.

2. Enrich com­post. Enhance com­post nutri­ents by sprin­kling in a few ashes so it looks like a fine pow­der. Adding too much, though, ruins compost.

3. Com­post­ing cit­rus rinds. In a bucket of wood ash, place rinds of cit­rus or any­thing that is hard to break­down. Make sure to cover the bucket.

4. Cal­cium lov­ing plants. For calcium-loving plants like toma­toes, sprin­kle and spread out ¼ to 1/8 cup (NOT MORE) right in the hole when plant­ing. More is not bet­ter. It should look like a pow­dered baby’s butt.

5. Block gar­den pests. Spread evenly around gar­den beds, ash repels slugs and snails.

6. Con­trol pond algae. One table­spoon per 1,000 gal­lons adds enough potas­sium to strengthen other aquatic plants that com­pete with algae, slow­ing its growth.

7. De-skunk pets. A hand­ful rubbed on your dog’s coat neu­tral­izes that famil­iar lin­ger­ing odor.

8. Hide stains on paving. This Old House tech­ni­cal edi­tor Mark Pow­ers absorbs wet paint spat­ters on cement by sprin­kling ash directly on the spot; it blends in with a scuff of his boot,

9. Clean glass fire­place doors. A damp sponge dipped in the dust scrubs away sooty residue.

10. Make soap. Soak­ing ashes in water makes lye, which can be mixed with ani­mal fat and then boiled to pro­duce soap. Salt makes it harden as it cools.

11. Shine sil­ver. A paste of ash and water makes a non­toxic metal polisher.

12. Kill moss in the lawn. Sprin­kle lightly over lawns that have moss problems.

13. Tooth­paste. In the old days before tooth paste, ash was used to clean teeth. The poten­tial bio-hazards in the mod­ern world are the chem­i­cals used in fire starters, newsprint, and mag­a­zine inks. Using bak­ing soda instead tastes much bet­ter and is a com­mon practice.

14. Clean­ing white boards. Ashes are good for clean­ing white boards that have been marked by grease pen­cil or marker. It even works on per­ma­nent marker that has been mis-applied to a white board.

15. Melt ice. My per­sonal all time favorite. Keep con­tainer of ashes in car (or on the porch for side­walks) in the icy sea­son to add trac­tion and de-ice with­out hurt­ing soil or con­crete under­neath. In Alaska, we car­ried a shoe box of fine screened ash to get vehi­cles out of ice. Sprin­kle hand­ful of ashes out about a foot in front of the tires that have power (4 wheel drive –all tires; front wheel drive –front tires; rear wheel drive– rear tires). Drive right out of trou­ble as if you were on dry pave­ment. Elim­i­nates the use of salt for icy sidewalks.

Check out the com­po­si­tion of ele­ments in wood ash, below, from the Uni­ver­sity of Georgia.

Hope this gives you some ideas for what to do with all that wood ash from our unusu­ally long and cold winter,


Com­po­si­tion of Ele­ments in Wood Ash Mean and (Range) taken from analy­sis of 37 ash samples

Macro ele­ments in aver­age %, range of 37 sam­ples, highest %

Cal­cium 15 (2.5–33) 31 Potas­sium 2.6 (0.1–13) 0.13 Alu­minum 1.6 (0.5–3.2) 0.25 Mag­ne­sium 1.0 (0.1–2.5) 5.1 Iron 0.84 (0.2–2.1) 0.29 Phos­pho­rus 0.53 (0.1–1.4) 0.06 Man­ganese 0.41 (0–1.3) 0.05 Sodium 0.19 (0–0.54) 0.07 Nitro­gen 0.15 (0.02–0.77) 0.01

Micro ele­ments or Trace Min­er­als in mg, range of 37 samples

Arsenic 6 (3–10) Boron 123 (14–290) . Cad­mium 3 (0.2–26) 0.7 Chromium 57 (7–368) 6.0 Cop­per 70 (37–207) 10 Lead 65 (16–137) 55 Mer­cury 1.9 (0–5) . Molyb­de­num 19 (0–123) . Nickel 20 (0–63) 20 Sele­nium 0.9 (0–11) . Zinc 233 (35–1250) 113

Other Chem­i­cal Properties

CaCO3 Equiv­a­lent 43% (22–92%) 100% pH 10.4 (9–13.5) 9.9

% Total solids 75 (31–100) 100