Two things kill the soil on most of our public and commercial
landscapes and many residences in Grants Pass: weed cloth and fine bark mulch, also
called Red Death, often used in combination.
Under the influence of water and gravity, dead soil compacts nearly as
hard as rock. Roots won’t grow in it;
they grow on top of it, just under the cloth, under the bark or gravel covering
the cloth, or in the Red Death. Storm water,
instead of percolating into such soil, runs off into streets, down storm
drains, and pollutes our river.
Weed cloth (and its cheap relative, black plastic) kills
soil by stopping the movement of worms and other soil life. Worms under the cloth, unable to get to food
on the surface, eventually run out of food under the cloth and starve. Ants, the other great soil aerators, are not
able to live under weed cloth either; nor are any other insects. With no life to lighten the soil beneath the
cloth, it compacts and loses oxygen, which roots need to breathe. Any further root growth is on top of or just
under the cloth, on top of the dead soil.
One might think it’s a good idea to put landscape cloth on
paths under gravel or mulch, to make the soil compact and keep it that
way. But roots will grow on top of or just
under the cloth; this gardener recently dug and cut out a cottonwood root that
had grown 8 inches high across a path of cloth covered with gravel over a mere
7 years.
Another problem with weed cloth and plastic is that mulch
will not stick to it, and it soon shows along the edges and anywhere the soil
is humped, by the growth of roots for instance, and where it shows, it’s ugly.
Fine bark, or Red Death, kills soil by leaching bark’s toxic
natural preservatives into the soil. Trees
make chemicals in their bark to protect themselves from insects, fungi, and
bacteria. Grind it up, break the plant
cells, and those preservatives are released to leach into soil, where they
quickly kill insects, fungi, and bacteria.
Dead as a doornail, the soil compacts under the influence of water, and
roots begin to grow on top of the soil, in the bark.
Neither weed cloth nor Red Death kills plants directly, but
some plants cannot stand compacted soil, sicken, and die. That’s why businesses have pansies and
petunias planted in blocks of potting soil, surrounded by Red Death. Most common landscape shrubs in our town can
take compacted soil, or they don’t last long and aren’t used by
landscapers. But they grow slowly and
are not healthy in dead soil.
Weeds grow regardless; gravel or fine bark are dandy
seedbeds for them, even on top of weed cloth.
They don’t have to be big to be ugly weeds; ugly little weeds spread
just as readily and look just as ugly.
Seeds are tracked in and fly in.
Roots under the cloth find their way out along the edges. So it doesn’t even work to stop weeds.
Larger screened bark, shredded wood-bark mixes like Walk-on
fir, and chipped wood or trimmings do not kill soil, as the preservatives are
kept in the bark. It is the bark dust
and small particles that leach enough preservatives to kill soil. Since larger barks keep their preservatives,
they last a lot longer. The larger the
bark, the longer it lasts, but walking is easiest on Walk-on and ¾” nugget, and
Walk-on fir sticks well to slopes.
