Using Wood Ash in the Garden
Image by Jupiter Images 
People often ask me if it's safe to put ash from a fireplace on the garden.
The answer is yes: homes with wood stoves and fireplaces for winter heat and backyard fire pits or built-in outdoor fireplaces create many tons of ash that can be recycled in our gardens. If you intend to recycle ash from these sources, burn only plain paper or newsprint and wood; do not include glossy paper, staples, nails, charcoal or bones. Wood ash is a rich source of potash, with an average N-P-K rating of 0-1.2-2. It provides calcium and many trace minerals and will raise the pH of the soil, commonly referred to as sweetening the soil. Because it raises the pH, apply ash only to those areas of the garden, or particular plants in the garden, that benefit from sweet soil, such as some vegetables, lavender and lilacs. Do not apply it to plants that need acid soil, such as rhodos and blueberries. You can also compost ashes—just be sure it doesn't make up more than five per cent of your total compost pile. Fall is the best time to distribute ash in the garden; that way it can settle in and release its nutrients the following spring. Generally ash is applied every two years at an application rate of 2 pounds per hundred square feet (.9 kg per 38 square metre), and is lightly raked into the top inch of the soil prior to planting. For established plants, sprinkle 1⁄4 cup (50 mL) within the drip line every two years. Next time you clean your ash drawer, fireplace or fire pit, be sure to look around the garden for a place to recycle the ash. Your sweet-soil loving plants will thank you.
Ornamental plants that prefer sweet soil:
- Lilacs - Clematis - Virginia creeper - Passionflower - Sweet peas - Japanese anemones - Nasturtium - Zinnia - Peonies - Phlox
Herbs that prefer sweet soil:
- Lavender - Thyme - Rosemary
Vegetables that prefer sweet soil:
- Beets - Cauliflower - Cabbage - Swiss chard - Leeks - Melons - Onions - Parsnips - Spinach