The lone voice of horticultural reason

Don’t mulch your perennials with wood chips or shredded hardwood

The more things change, the more they stay the same. Years ago, somewhere on this site, I wrote that mulching perennials with wood chips or shredded hardwood was a sin – it didn’t look right, and besides, when the time came to dig up plants for division, move stuff, dig new holes, etc., you were always dealing with these great shards and mats of wood gumming up the proceedings.

Then I let my readers beat me back into my cave. Shredded bark and wood chips were just fine for perennials, they said, they eventually grow so as to cover most of the wood mulch, and life’s too short to mulch trees and shrubs with wood mulch, then have to bring in some other form of organic – dried grass clippings, compost, cocoa or pecan husks – to mulch around the perennials.

Well, it turns out I was right the first time, though not for the reasons I thought. (New readers, you’ll get used to it). Last week I had the great privilege to speak in Kenosha, Wisconsin, at the 20th annual Wintergreen Conference, and heard a talk on developing perennial plant communities by a fellow speaker, Roy Diblik, owner of Northwind Perennial Farm in Burlington, Wisconsin.

It was one of those life-changing moments. The dude knew his stuff, but the reason he could speak it with such compassion and conviction is that he is not a trained horticulturalist – he has learned by doing.

And one of the many astute points he made was that most of us don’t grow perennials, we enable them to linger. They linger for three, or five, or maybe ten years, and then, quite often, they die. And they die because we do not grow them as they are accustomed to growing in the wild.

In the wild, they do not grow where two or three inches of wood surrounds them and slowly breaks down into the soil, only to be replaced by more wood. Yes, wood mulches are organic, and yes, as they break down they add organic content to the soil, but not the type of organics that perennials need. What Diblik does is mow over all his perennials – he’s designed some fabulous public gardens around the country – up to seven times with mulching mowers, then leaves the “duff” – the shredded plant parts – in a layer atop the bed.

This forms the late-season and over-winter mulch, such that after a few years the perennials are replenished not by wood but by their earlier generations. And they thrive.

Researching Roy afterward I came upon an interesting article on him and his plant growing philosophies in the Chicago Tribune. I also heartily encourage you to visit his website,

By the way, Roy is no fan of mulching around trees and shrubs with wood mulch, either, though admitted to me that they are bigger engines than perennials and seem to do better. But to thrive, his schtick is to mulch around trees and shrubs only with other plants – groundcovers and, most often, low sedge grasses. Hmmm…


Don Engebretson
The Renegade Gardener