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, www.northwindperennialfarm.com

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’t plant Japanese and European Barberries (Berberis thunbergii and Berberis vulgaris)

This is by no means a scoop. These two Barberries have been labeled as invasive in twenty states, and the time has come when I join the cadre of purists calling for the cessation of nursery sale of these two types of very attractive Barberries. If the call on other invasive garden plants such as European Buckthorn (Rhamnus cathartica) and Princess Tree (Paulownia tometosa) had been made earlier, they wouldn’t be upsetting plant and wildlife habitat across three-quarters of America.

It’s a pity. Japanese Barberry varieties include all the cool ones, ‘Burgundy Carousel’ and ‘Helmond Pillar’ and ‘Golden Ruby.’ European Barberry is not found in the trade much, a low-growing form that hasn’t been cultivated for snazzy colorful foliage. Still, all are to be avoided.

Berberis thunbergii ‘Golden Ruby’

As with all invasive plants that start out as our allies, Barberries have proven adaptable to a wide variety of growing conditions – full sun, shade, open spaces, woodlands. They are drought resistant, a nice quality for a landscape plant but always an evil trait when found in any non-aquatic invasive.

How do they get into the wild (keeping in mind that “the wild” is as often that nice little patch of wooded parkland down the street)? People plant them in their yards at the edge of woods, or bordering some other type of public or private, natural area. Branches touching the ground can root to form new plants. They slowly get away.

More often, it’s the fruit. As one would guess, Barberries bear berries. Birds and other wildlife eat the berries, which contain seeds, poop them a mile or more away, often into the wild, and up pops a new Barberry. Barberries produce high numbers of seeds, with a germination rate of around 90%.

In the wild, these small, fiercely hardy shrubs take over, crowding out native plants and reducing vegetation used as food and shelter for all manner of wildlife. They are particularly tough on deer populations, as deer don’t like to chomp on the tough, woody stems containing prickly barbs.

As I said, it’s a pity, but the Renegade Gardener is officially saying “no” to Japanese and European barberries for personal use and in my landscaping business. It will take at least five years for the nursery industry to follow suit; outright, governmental bans on nursery sales tend to dawdle. In the meantime, you can do your part by no longer purchasing them.

Most upsetting is I’ve now lost one of my favorite lines from one of the tree and shrub talks I give to the public. Barberries are essential, I have told audiences many times, for planting anywhere neighborhood kids in shorts in summer can be found rooting around your landscape searching for errant balls. To keep small, near-naked kids off your property, plant Barberries.