Collect the ashes in your fireplace now.

never use hot wood ash....

 Now that winter is coming to a close you can utilize a valuable soil amendment from your fireplace: Wood ashes.

They are rich in Potash which “sweetens” the soil by raising the pH (more alkaline).

Sweet soil is the balm of lilacs and other flowering shrubs. If your lilacs produce too few flowers, Potash can help. 

Composting ashes is an ideal way to put them to use in the garden. Decomposing materials in the compost pile can become acidic and wood ash is more alkaline and helps offset this.

Apply regular wood-ash applications on soil beneath your shrubs in fall, winter and early spring. 

You cannot apply too much; rain and snow dilute the concentration of Potash considerably. Empty thoroughly cooled fireplace ashes into a large container and then pour a large amount in a wide circle beneath the drip line of  mature lilac shrubs. For small ornamental, herb and vegetable plants,  pour about a cupful beneath them.

wood ashes

Here are plants that prefer sweet soil:

Ornamentals:
Clematis, Gypsophila,  Japanese anemones, Lilacs, Madonna Lily, Nasturtium, Passionflower, Peonies, Phlox, Sweet Peas, Virginia Creeper

Herbs:
Lavender, Rosemary, Thyme

Vegetables:
Beets, Cauliflower, Cabbage, Leeks, Melons, Onions, Parsnips, Spinach