Moderately alkaline soil favors the growth and productiveness of many garden plants. Wood ash is alkaline. So you should only apply the ash if your soil pH or acidity factor is less than 7 on a soil test. The only way to be certain is to get a soil test done. Wood ash changes the chemistry of the soil. It sweetens the soil.
How much wood ash? Apply 10-20 pounds of wood ash per 1000 square feet each year. No garden? You can also use wood ash on your lawn using about 15 pounds per 1000 square feet. Be careful not to burn your lawn though! And if you want your lawn or garden to be more green, you'll have to add nitrogen. There's none in wood ash and so it can't be considered a complete fertilizer for this reason.
Vegetables & Fruits that like Wood Ash:
apples, asparagus, beans, beets, broccoli, Brussel sprouts, cabbage, cantaloupe, carrots, cauliflower, celery, collard greens, cucumber, lettuce, onion, parsnip, pea, rhubarb, squash, sweet pea
Since ashes are alkaline [base] so they can be a great substitute for lime. So if you're told to spread 10 pounds of lime, you can do the same with 15-20 pounds of wood ash. I compost a ton of fruit scraps in my garden which are very acidic. The ashes help offset this addition by raising the pH. Lime does this too~ raises the pH of the soil. It's really all about balance.
We spread our wood ash in the vegetable garden all winter and work it into the soil well before the planting season begins. You don't ever want wood ash to come in direct contact with any of your seed or the roots of the plant. If you can, keep the ash in a container by your garden and sprinkle on a layer now and then. This way you won't raise the pH of the soil too much at once.
So why do I advocate using it on your lawn and garden? 1) Because the ash has to go somewhere and this is a convenient way to dispose of it 2) If derived from hardwood [more nutrients than softwood] this wood ash is still highly beneficial despite its lack of nitrogen.
Another advantage is that wood ash seems to kill weeds. In the spring, I don't have to weed my beds because the ash has already killed all the weeds. I think this is because the wood ash is a base and acts to kill the weeds (remember many plants like to be in that more acidic 4-5.5 pH range) so it must be raising the soils pH levels to deadly levels.
Keep in mind: I don't grow acid loving plants like blueberries in my raised beds. If I did, I wouldn't be able to add the wood ash. I grow those types of plants in different parts of my yard to keep them separate. You might want to do the same, even if it requires some transplanting.
- Use only good quality hardwood ashes - stove ashes okay, burn pile not-so-much
- No ashes from BBQ, grills, cardboards, plywood, painted or pressure treated wood