Tuesday, October 21, 2008

Mulching blankets beds, trees for winter

By Beth Botts Chicago Tribune

A layer of mulch over the soil does plants no end of good.

It insulates, keeping the temperature more steady and protecting roots from cold snaps and hot spells. It keeps soil moisture from evaporating, so you needn't water as often.

It shades weed seeds, so they avoid enough light to sprout. Around a tree trunk, it keeps bark-chewing string trimmers and lawn mowers at a safe distance.

And, if the mulch is organic -- anything that once was a plant -- it breaks down to feed microorganisms that then nurture plants and make soil a better home for roots.

Because autumn is a good time to add a little mulch over flowers and trees before they go dormant, here is some food for thought before you shop for mulch:

• Consider the source.

Most commercial organic mulches, apart from straw, are wood byproducts from the lumber industry. Bagged mulches from reputable garden centers or home-improvement stores or bulk mulches from landscape-supply companies are usually clean and safe.

Cheap bags of mulch, including the kind often sold at gas stations, might contain shredded construction debris or other waste with toxic chemicals, metals or lead paint.

Cypress mulch, even though reputable stores sell it, might come from clear-cutting virgin trees in Southern wetlands, a practice that threatens coastal areas.

• Choose mulch for its purpose.

Medium-textured mulch such as shredded hardwood will work in most places. But in a permanent layer around trees, big chunks -- such as pine bark nuggets -- will last longer. For perennial beds, though, something finer works better.

In vegetable beds, use something fluffy that easily decomposes, such as straw. Gravel mulch, recycled glass or recycled rubber tires will cover the ground but won't improve soil the way organic mulch does -- and the pieces tend to stray across the yard.

For areas where you never plan to dig, a layer of landscape fabric under mulch helps deter weeds. But you should replenish and tidy the mulch periodically to keep the fabric hidden.

Mulch color is a matter of taste. The most classic look: undyed dark-brown mulch.

• Buy bag or bulk? Mulch is sold in bags (usually containing 2 or 3 cubic feet) or by the truckload (measured in cubic yards; a cubic yard is 27 cubic feet).

Bagged mulch is much more expensive but easier to handle, especially when you have no room for a pile of bulk mulch. Another advantage of bags: You can buy different kinds for different purposes.

Bulk mulch can be ordered at varying prices from garden centers or landscape-supply companies. When you shop around, explain specifically how you plan to use it and price the material recommended for that purpose.

• Plan. To figure out the area to be mulched, break it down into smaller shapes, such as rectangles or circles; then measure them and figure the area of each. (Don't remember how? See math.about.com/library/blmeasurement.htm). Add the figures to get the total area. Then decide how deep you want it: 1 to 2 inches for perennial beds, 3 to 4 inches over tree roots.

One cubic foot will cover about 4 square feet 3 inches deep; 1 cubic yard will cover about 110 square feet at that depth.

Overbuying mulch not only wastes money but might tempt you to spread it too deep, which can obstruct water and air to roots.

Removing old mulch isn't necessary; just spread a new layer on top so old and new together reach the right depth for plants.

• Find it free. Fallen leaves are an excellent mulch for flower and perennial beds, especially when shredded. An electric blower-vacuum with a shredder costs about $75.

For trees and shrubs, consider asking landscapers or utility crews to dump a free load of wood chips from tree trimming -- but not on the lawn, where the pile will kill the grass.

Don't use just-shredded wood chips in flower or vegetable beds. They are too chunky, and the early stages of decomposition will compete with the plants for nutrients.

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