CULT: Solarizing

Everyone,

For those of you who are  reworking old iris beds consider solarizing. 
I realize "this may not be feasible for everyone", but for those who can
get at least a dry, two week hot spell in the summer the benefits can be
staggering.

How many of you struggle with weeds?  Gone with solarizing.  How many
complain of rot or poor growth?  Gone with solarizing.  You will be
amazed next year at the tremendous growth and bloom of your iris if you
solarize this summer.

The basic idea for most parts of the country is to place transparent
polyethylene tarps over moist soil in summer and let the sun heat the
soil to to a temperature that kills many soil pests and brings favorable
physical and chemical changes in the soil itself.  

Here is what to do:

Remove weeds, debris and large clods, and prepare soil as if you were
going to plant.  With a sprinkler, thoroughly water the area. 
(Alternatively a flexible soaker hose could be snaked under the plastic)
. Anchor transparent (not black) plastic sheeting over the soil by
burying the edges in a trench around the wet area.  If you are in a
windy region , or one where nights cool down considerbly, use 4 mil
plastic.  Otherwise a thinner sheet will do (2 mil).  Pull the plastic
tight over the surface to prevent air pockets, which retard soil
heating.  Leave the plastic in place for at least two weeks.  Four to
six weeks is even better, but two weeks should give good results.  The
longer the tarp remains over the damp soil the deeper the heat
penetrates.  

Then remove the plastic and allow soil to dry to workable texture, then
plant. It is best to cultivate shallowly, less than two inches, to avoid
moving viable weed seeds to the surface.  The beneficial effects of the 
treatment should last about three years.  

Take care of your beds now and reap the rewards next year!

Rick Tasco
Superstition Iris Gardens
Central California
Zone 8
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