“Organic Bob” tells NE Minneapolis neighbors: “Wiggle that shovel”


I went to “Organic Bob” Dahm’s Sustainable Yards workshop hoping to talk neighbors into renting a core aerator with me. A core aerator needs its 350 lbs. to jam the pinkie-sized core removers into the grass thatch and soil, compacting the soil further, even while bringing up nutritious organic matter that composts naturally.But it turns out my father’s favorite trick with a spading fork should do what I really wanted to accomplish, loosen up the compacted soil.

Instead of using the big machine – wiggle that shovel. About every two feet, “Organic Bob” Dahm said, thrust a shovel straight into the yard. Pull back on it, maybe wiggle, so as to raise the grass just a little bit. You’re creating a pathway for water, roots and air. He suggests then spreading about a quarter inch of compost, raking the compost so that the grass blades are standing up out of it again, then watering. You can substitute a spading fork for the shovel but it has less leverage and depth, you’ll be working harder and longer. It’s okay to do the entire process over a patch of lawn, like 10 ft. by 10 ft., and then next time you’re out, move on to the next patch (rather than doing each operation on the whole lawn at once). If there’s a lot of time between efforts, the lawn may look like a quilt in the first year, but should even out in the second year.]

Sheridan Neighborhood Organization underwrote the workshop. Dahm had done a similar session in Linden Hills and has a landscaping business. He helped listeners understand that “organic” is not just a different kind of chemical, but an entire practice that works with the “soil food web” to eventually cut down the amount, time and expense of yard work, yielding a 95 percent weed free lawn.

After a talk at East Side Neighborhood Services May 17, many of the 30 attendees went out with Dahm and the organizers to two homes on Fifth Street NE to demonstrate techniques. He also talked about alternatives to lawns, working with shade, sloping yards, incorporating edibles into the landscape and looking at a lawn as a series of outdoor rooms in order to use turf only where really appropriate.

I’m a gardener who’s learned from books and workshops like this; some of Dahm’s material was familiar, some new to me or particularly well put, and those will be the notes I’ll share with you.

About how the bacteria and fungus in soil help the plants: “These little guys are chewing on the plants and saying ‘hmm. I think you’re low in calcium today,’ and they go out and get what the plant needs and brings it back, with water.” In a not-healthy yard, an anaerobic (no air) bio-slime runs rampant. “Broadleaf plantain indicates pools of fermented bio-slime under the soil. We call it the drunk of the plant world.” To get rid of the weed for good, break up the compacted soil and get some air into it.

Earthworms in excess, indicated by an uneven, bumpy yard surface, can also cause those anaerobic bacteria conditions.

Dandelions are a sign of compacted, slightly alkaline clay soil. Their long tap roots break through the compaction and pull good chemicals up. Clover is a sign of nitrogen deficiency.

“Soil is like the stomach of the plant, it’s where the digestion takes place.” Bob Dahm said urban yards have been depleted of their carbon because the organic matter has been eaten up by high nitrogen fertilizers.

Weeds would eventually work themselves out of a job, in longer than our lifetimes. Dahm said lawns are a case of arrested development: Much of our area was oak savannah, and we’re stuck in a “pre-grass” state. “The weeds’ job is to convert the soil” to something more usable.
Should I renovate my yard or replace, start over? Dahm applies the “four step test.” Walk around the yard, and if four or more out of 10 steps are on weeds or problem conditions, you would be better off starting over.

When replacing, remove the top inch or two of turf. Hand fracture the soil deeply. Add amendments. Till to 8 inches deep.  If you’re using sod, “wean it off of water, stress it a bit” to challenge the roots to go deeper, less dependent on watering.

Other wisdom:
Establish “communities” of species. Example: oak, surrounded by hazelnut, maybe raspberries – the “edge” growers, the healthiest part of a forest. Apple with alpine strawberries and daffodil (a relative of the onion) to keep rodents away and attract pollinators early in the season, beneficial to the apples.

“I rent. I don’t have time for a yard,” Dahm said. “But if I did, I would mulch the perimeter as a warning track.” If he sees clover or creeping Charlie starting across the four inch deep track, he can deal with it there.
At sidewalks, cut an angle into the dirt to make a wide V-shaped channel that will collect water that will then absorb into the lawn. Sod can be wrapped over that angle.

Weed removal: “Maim rather than amputate,” as plants will re-grow if they are cut off, whereas if they are injured, they spend all their resources trying in vain to repair. He talked about a selective torch, and strong vinegar solutions that can be brushed on to wilt leaves.

Don’t like grass? Try German chamomile. “It’s a good idea to do a mix,” whatever you do, Dahm said. Any monoculture, if conditions turn bad, could mean the entire lawn dies out.