Archived Story

Mulch saves moisture for plants

Published 7:13am Monday, June 30, 2014 Updated 9:14am Monday, June 30, 2014

Bunkey isn’t too fond of weeding, especially when the air temperatures are in triple digits and the humidity is not far behind. Shortly after he moved to his present home, his neighbor, George the Master Gardener, tipped him off to mulching.

George quoted Jill Clapperton, the principal scientist for a company called Rhizoterra in Florence, Montana.

She maintains that providing shade to the soil, that is, by mulching, one not only reduces evaporation but also keeps “underground livestock,” earth worms, soil microbes and other beneficials, cool and working for the gardener.  If the soil gets too hot, worms will migrate deep in the soil to find water and avoid the heat.

Another expert, J.J. McEntire, a USDA scientist, said as early as 1956, that 100 percent of moisture is used by the plant for growth when the soil temp is 70 degrees. When the soil temp hits 100, only 15 percent is used for growth. The rest is lost to evaporation and plant transpiration. When the soil reaches 130 degrees, all moisture is lost and at 140 degrees, most of the soil bacteria die.

He contends that when the soil temp is 68 degrees, most organisms in the soil have “fully functioning populations and are actively reproducing.

There is lots of mineralization going on and plant roots are taking full advantage of this activity. Mycorrhizal fungi also work at the same optimal temp so there is high speed transport of nutrients going on.“ In plain English, the plants are growing like weeds.

Bunkey has been mulching using four to six layers of damp newspaper under his mulch. This is thick enough to prevent seeds from sprouting as most weed seeds need light to sprout.

Last week, he was poking around a hardware store, (guys do this for entertainment, you know) when he discovered a shortcut. There, right in front of him was a roll of heavy brown paper, 3 feet wide.

This building paper is thick enough to prevent seed sprouting and sturdier than wet newspaper.

He had put his knee though newspaper more often than he wanted to admit.

Not only that, if he laid newsprint on a stick, the stick popped right through it, leaving a nice hole for a weed to pop up.

He still needed the newspaper in some spots, but rolling out feet of paper cover rather than laying a few feet at a time made for quick work of mulching.

When mulching, don’t put the mulch right up to your plants. This can lead to rotting of the plant.

Of course, this means that there will be weeds in the rows but Bunkey, (or more often, Petunia) simply pulls the weeds as she harvests.

Even though there is enough moisture in the soil now, we know that there will be weeks with no rain. Since Bunkey waters with city water (and he is so tight with money, the buffalo on his nickels bellow), he wants to conserve any moisture he has.

Mulching in a dry period can reduce soil evaporation by as much as 2 inches and that is two weeks supply of moisture.

Get down on your knees and mulch. Your back may be achy, your knees worn out of your jeans at the end of the day, but you will be able to sit under a tree and have a cold one when it’s 100 above and so wet, moss is growing on your north side.


Bev Johnson is an Extension Master Gardener in Otter Tail County.


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