Mulching your flower beds may require a math lesson

The rainy and snowy weather over the last few weeks may have delayed your fall cleanup work. I typically do not mulch established perennial borders but leave the perennials up for the winter and let enough fall leaves blow in to cover the ground but not mound up and bury the perennials. This leads to more of a natural (not manicured) look, which I prefer.

If you prefer a neat and tidy look for the winter, cut back your perennials and top dress the bed with a light layer of mulch (1 inch maximum). There is no need to wait until the ground freezes to mulch, as many references recommend.

To calculate the amount of mulch needed for a bed, first convert all measurements to feet. One foot equals 12 inches. To figure the square feet of a bed, multiply the length of the bed times the width. To convert the depth of mulch to feet, divide the inches of mulch you intend to apply by 12. If your mulch is to be 1 inch deep, divide 1 by 12. This gives you .08-foot depth of mulch.

Use the following formula to calculate the amount of mulch needed for 1 inch of depth over a bed that is 15 feet wide by 20 feet long: Fifteen feet times 20 feet equals 300 square feet of bed space. One inch divided by 12 inches equals .08 feet. Three hundred square feet times .08 feet of mulch equals 24 cubic feet of mulch. One cubic yard of mulch is 27 cubic feet, so divide 24 cubic feet by 27, which equals .89 cubic yards. Your order should be one cubic yard of mulch.

Bagged mulch comes in different sizes. Typically, 2- or 3-cubic-foot bags work well for small beds. For the bed above, you would divide the 24 cubic feet of mulch required by the amount of mulch in the bag — 24 cubic feet divided by 3 cubic feet per bag equals eight bags, and 24 cubic feet divided by 2 cubic feet per bag equals 12 bags of mulch.

For this bed, it is probably less expensive to buy the mulch in bulk. Be sure to include the delivery cost for bulk mulch when making a comparison.

• It is a good idea to sharpen and clean garden tools before putting them away for the season. Sharpen spades with an electric hand grinder and put the bevel on the inside edge of the spades.

Wear ear and eye protection for this task because it is noisy and sparks will fly as the grinder works. Move the grinder steadily back and forth to create the sharp edge and avoid burning the metal.

Well-maintained tools make gardening much easier. Use pegboard on your garage walls to hang and organize tools.

• If your garage is unheated, it is best to store any liquids in the basement. Have your snowblower serviced before the first big snowfall when repair shops may get backed up with repair and maintenance work.

• Tim Johnson is director of horticulture at Chicago Botanic Garden, chicagobotanic.org.