arts
SHORTS
Found-object sculptor Jud Turner’s completed freestanding model of
a Columbia mammoth skeleton is about to make its way to the Moses
Lake Museum and Art Center in Moses Lake, Wash. The mammoth, made
completely from recycled farm equipment, will be displayed in an exhibit
highlighting the history of the Columbia Basin. — Dante Zuñiga-West
PHOTO BY TODD COOPER
gardening
BY RACHEL FOSTER
Got Clay?
Crushed rock addresses some sticky issues
I
n making our last garden on a steep, damp piece of
hillside we brought in a lot of material: quarried basalt
rock for retaining walls, round rock for drains, an
ocean of gravel. When we moved house a few years ago,
I was aiming for a garden with a lighter carbon footprint.
Among other things, I hoped to save energy by bringing in
as little material as possible. As I learned more about our
new yard, those hopes went down the drain, so to speak.
We discovered, during remodeling, that the soil
immediately around the house is pure clay with a thin veneer
of soil. That explained why rain and irrigation water runs
straight to the bottom of the garden, where it drains into an
alley and forms near-permanent, year-round puddles. Shrubs
have shallow root systems, suckering madly and showing
drought stress at the drop of a hat. Other areas of the garden
have decent soil, but the lie of the land and impervious
underlying subsoil combine to ensure that some spots are
squishy and anaerobic for much of the year.
Gray, stinky and wet immediately after digging, the
saturated loam loses its odor and turns a healthy brown
within an hour or less of being exposed to the air. In a
few days it is crumbly and useable in a raised bed. What
about the true clay, though? What, if anything, can be
done to transform a substance you could mold into bricks
into something you can plant in? The usual suggestions
for breaking up clay — adding plenty of organic matter,
for example, seem more applicable to lightening up clay
loams, not the pure stuff we inherited.
A few months after we moved, I heard a talk by Maurice
Horne of Joy Creek Nursery in Scappoose in which
he touted the value of a crushed rock product known as
quarter-10 for lightening clay soil. Quarter-10 is crushed
20 JANUARY 19, 2012
EUGENE WEEKLY
river rock with a range of particle size between one 10th
and one quarter of an inch. Heavy clay loams consume
organic matter which must constantly be replaced, while
quarter-10 is a longer-term investment. I’ve known for
years about spreading quarter-10 on soggy lawns to make
them walkable (an idea that also originated with the folks
at Joy Creek) ever since garden writer Anne Lovejoy wrote
about it in a gardening column. It works.
Horne now promotes a more radical use of the stuff:
actually mixing it with the soil to improve drainage, in
order to accommodate drought resistant plants and reduce
summer water use. I disliked the idea of encouraging
gardeners to bring in truckloads of heavy material that
has to be mined, washed, and transported using masses of
energy and water. How ecologically sound is that? Now, I
am chagrined to admit, I am doing it myself. Does it work?
The answer appears to be yes.
To begin with, I used a mix of quarter-10, compost and
our own loam and to make shallow raised beds over the top
of heavy soil that is wet nine months a year. This allows
us to grow a variety of plants in place of the shallow-
rooted turf that was there before. The plants love it, and
the particles in the gravel are small enough that they don’t
interfere with cultivation. In some areas we also apply
quarter-10 as a mulch on heavy soil. It looks nice and
makes weeding much easier.
Using the stuff to open up impenetrable clay is still in
the experimental phase, but it does look promising. Here is
what we do with clay that is above the water table:
We break up the clay with a shovel to a depth of eight
to 12 inches, leaving it in large chunks, and roughly mix
the chunks with quarter-10. This permits some air to
penetrate, allowing for deeper wetting and drying, freezing
and thawing cycles. These processes cause the clay nearest
the surface to disintegrate into crumbs. When the moisture
content of the crumbs is exactly right, they break apart
when cultivated and can be mixed more thoroughly with
the quarter-10 as well as organic amendments.
I’d love to hear from readers who have turned clay into
soil. Compost tea, probiotics and judicial applications of
lime are said to help, and we will try them all. But I’m
convinced that getting air into the soil is the fi rst step.
Quarter-10 gravel helps to make that possible. We’ve
already planted trees and shrubs in this rough mixture, and
they seem to be thriving.
ew
Rachel Foster of Eugene is a writer and garden consultant. She can be reached
at rfoster@efn.org
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