Fall Gardening

Friday, November 14th, 2008 by Jenny Watts
    • Japanese maples and snowball bushes are some of the most colorful shrubs in the fall. Plant them now and give them a head start on spring.
    • Check houseplants for insects. Spray leaves with insecticidal soap and wipe them off to leave them clean and insect-free.
    • Empty birdbaths and fountains and cover them for the winter, to prevent water freezing and cracking the bowls.
    • Transplant shrubs that need to be moved this month. It’s also a good time to transplant natives.
    • ‘Tete a Tete’ Narcissus are the cute little yellow daffodils that are popular in pots. Plant some now for fragrant blooms next spring.

Wood Ashes in the Garden

Cool fall mornings call for building a fire in many homes. And at some point that means there will be a bucket of wood ashes to dispose of. Should these ashes be dug into the garden or the compost pile? That’s a question with a complex answer.

Wood ashes contain nutrients, specifically calcium, potassium, magnesium and other trace elements. Hardwoods produce three times as much ash per cord as do softwoods and five times as many nutrients, although the amount of major nutrients is small in either case. Wood ash has a very fine particle size, so it reacts rapidly in the soil.

But more importantly, wood ashes are very alkaline. They contain about 25 percent calcium carbonate, a common liming material, and have a pH of 10.4. So a little goes a long way, and adding large amounts can do more harm than good.

The pH is a measure of the acidity or alkalinity of soil measured on a scale of 1 (acid) through 7 (neutral) to 14 (alkaline). Nutrients are most readily available to plants when the soil is slightly acidic, with a pH of 6.0 to 6.5. As soil alkalinity increases and the pH rises above 7.0, nutrients such as phosphorus, iron, boron, manganese, copper, zinc and potassium become chemically tied to the soil and less available for plant use.

The majority of food crops prefer a neutral or slightly acidic soil. Some plants, like potatoes, blueberries and strawberries, prefer more acidic soil and plants in the broccoli and cabbage family prefer alkaline conditions. Wood ash should never be used on acid-loving plants, or in areas where potatoes will be planted since wood ash can promote potato scab.

Specific recommendations for the use of wood ash in the garden are difficult to make because soil composition varies from garden to garden. Acidic soils (pH less than 5.5) will likely be improved by wood ash addition, and soils that are slightly acidic (pH 5.8 to 6.5) should not be harmed by them. You can apply up to 20 pounds per 1000 square feet annually, working it into the top 6 inches of soil.

However, if your soil is neutral or alkaline (pH 7.0 or greater), find another way to dispose of wood ash. If you don’t know your soil’s acidity or alkalinity level, you can test it or have it tested for pH.

The best time to apply wood ash is in the spring when the soil is dry and before tilling. Wood ash that has been exposed to the weather, particularly rainfall, has lost a lot of its potency, including nutrients.

In compost piles wood ash can be used to maintain a neutral condition, ideal for microorganisms activity. Sprinkle ash on each layer as you build the compost pile. This is especially good if you have oak leaves or pine needles in your compost heap.

Use wood ashes with care, or bury them where you don’t plan to grow anything.