Mulching myths: what's true and new
Our garden writer seeks out a Northwest extension expert to update her mulching rituals and finds out that some of them — such as spreading chicken manure — need revising.
Can it really be time to think about mulching the garden . . . again? This task rolls around as rapidly and relentlessly as Christmas, so if you follow good gardening practices and mulch twice a year, why even bother to put the wheelbarrow away?
We all have our mulching rituals, and I figured mine could use an update. So before ordering the usual truckload of "chicken-and-chips" I called Linda Chalker-Scott of Washington State University Extension Urban Horticulture, author of "The Informed Gardener" (University of Washington Press, $18.95). This turned out to be a smart move because Chalker-Scott advised me that a number of my habits were rooted in myth.
I explained to her my late-winter drill, which is more about saving my back and making the garden look good than science. First I clean up diseased leaves and cut back mushy heaps of perennials. I leave lots of mess to cover up with mulch — isn't that the reward for all the work? I scratch a little organic fertilizer around roses, but mostly rely on the manure in the mulch to feed plants, augmented with compost during the growing season.
Then comes the hard work of hauling and spreading yards of a dark, rich mixture of chicken manure all rotted down with wood chips. Down on my knees and hands gloved, I spread the slightly stinky stuff as thickly as possible between plants. I'm careful not to bury the crowns of emerging perennials, or heap the mulch around trunks of trees and shrubs. I pile it more thickly around greedy plants like hostas and hydrangeas, and dig it into the bed where I'll soon plant sweet peas.
The result? Plants are nourished by the manure as they start their spring growth spurt, and the soil retains moisture as days grow longer and drier (we hope, and the sooner the better, please).
The immediate reward is that the garden looks tidy and fresh, the messy beds coated with a uniformity of dark mulch to show off the green of new foliages. Over time the mulch breaks down and improves the soil.
By late autumn, when I'm tired of gardening, I simply clean up and add more mulch around tender plants to protect them from cold. I never use a manure-rich mulch in the fall, because the plants shouldn't be stimulated to put out new growth that time of year.
Or so I thought.
"Fall is a great time to apply a feeding mulch to hardy trees and shrubs . . . although you wouldn't want to feed marginally hardy plants like palms in the autumn," says Chalker-Scott.
Her other myth-busting mulching advice:
• Steer or horse manure is better than chicken, which is so high in phosphates that it inhibits beneficial microbes in the soil.
• "Weeds love that!" says Chalker-Scott of feeding mulch, which turns out to encourage rather than suppress weeds. For effective weed control, she advises, cover a layer of feeding mulch (or compost) with a thicker, 4- to 6-inch layer of coarse, organic mulch like wood chips.
• Wood chips offer additional benefits: They're local and free (available from arborists); using them in your garden keeps them out of landfills, reducing your carbon footprint; they retain soil moisture and work as a slow-release fertilizer. Any disease in the chips doesn't transfer to healthy plant roots, as long as you don't dig the chips into the soil.
I admit I can't get over what wood chips look like, to which Chalker-Scott tactfully replies, "Wood chips are an aesthetically difficult choice for some people."
• To make the most of mulching, learn what kind of soil you're working with. "The best $9 you can spend is to get a soil test from the University of Massachusetts at Amherst," says Chalker-Scott (www.umass.edu/plsoils/soiltest/).
Will all this scientific, up-to-date advice change my mulching ritual? I'm thinking about doing a soil test, and am searching out a feeding mulch made with steer or horse manure rather than chicken. But I'll reduce my carbon footprint in ways other than by using wood chips, which means I'll continue pulling weeds by hand.
Valerie Easton is a Seattle freelance writer and author of "A Pattern Garden." Her e-mail address is firstname.lastname@example.org. Gabi Campanario is a Seattle Times staff artist.
Copyright © 2009 The Seattle Times Company
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