Designer Ann Nickerson plans a mulch experiment

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on February 07, 2009 at 8:00 AM, updated February 07, 2009 at 8:08 AM
The effect Ann is looking for: a garden bed with few weeds.

Most of us, at one time or another, have confronted the mystery of mulch. What's better: bark dust or garden mulch? I know I've thought about it many times. So has garden designer Ann Nickerson. The difference between Ann and me is that I fly by the seat of my pants. She, on the other hand, is determined to find the answer with a more organized approach.

A bed covered with shredded branches.

Here's Ann:

To mulch or not to mulch is not the question. We know why we should mulch.

It prevents moisture loss.
It reduces weeds.
It improves soil structure.

My dilemma is: Which mulch should I use?

When I lived on an acre in Aloha, the cost of the first application of 12 units of bark dust for my 15,000 square feet of garden borders sent me looking for cheaper alternatives. I found a neighbor we affectionately refer to as Farmer Ted who trimmed trees for a living. Ted was happy to drop off truckloads of freshly shredded plant material (garden mulch) for free. It was brighter and coarser than bark dust, but the price was right, and all the neighbors in our cul-de-sac joined in the bounty. It did a great job of keeping the weeds down.

Bark dust used as a top dressing.

When I moved to a small rental house, I went back to using bark dust. However, the landlord was concerned about carpenter ants and asked me to use garden mulch the next time. We bought a home in Hillsboro before it became necessary to re-mulch, but I took note of her concerns and of all the talk about garden mulch being better for the soil. I decided to dig in garden mulch when I renovated the garden. I have continued to use it as a top-dressing for the past four years.

I like the idea of being Earth-friendly, but I'm frustrated with all the airborne weeds from the neighbors or plants in my garden. I'm always fighting patches of little weeds. I keep asking myself these questions:

Is it a good idea to mulch my beds to prevent weeds with the same product I work into the soil to make plants grow? Can garden mulch really perform both these jobs?

Should I return to hemlock bark mulch to reduce my weeding? Won't it also improve the soil as it decomposes?

In early March, I plan to mix the present top-dressing of garden mulch into the soil along with organic fertilizer and then cover it with hemlock bark mulch. I'll watch it throughout the seasons and see if it continues to sprout hordes of tiny weeds. By next December I'll know the answer to my garden dilemma and share it with you.