Las Vegas, Photo By: Irene Hannestad
Spring is the time to begin thinking about the soil in your rose garden -- either renovating old soil in an existing garden or preparing for a new garden.
The four main elements of good rose soil are inorganic materials, organic materials, water and air. The
composition is best described as a loam. By definition, a loam is about 50% pore space, of which half
is water and half is air. The remainder of the loam is about 44 to 46% inorganic material and 4 to 6% organic
material. The inorganic material is a 3-1-1 ratio (or 60%-20%-20%) of sand, sediment or silt, and clay
respectively. The organic material is composed of humus, materials which have naturally decomposed.
Quite honestly, most of us don’t live in a world with perfect loam. We must create it. Here are some
pitfalls to watch for when building a quality rose soil.
Use caution when incorporating sand into heavy clay soils. Over time, this sand will settle to form
a hard pan below the soil’s surface much as if you were to put a concrete pad under the soil.
This will trap water and prevent good drainage.
Use caution when adding organic materials to improve existing soil or create a new loam. Too much
organic material will drive soil pH into the acid range, and make insoluble precipitates of many
of the nutrients needed for the roses. In acidic soils, limestone may be needed to raise soil pH.
Organic matter must first consume nitrogen before it can decompose. When adding undecomposed organic
materials, don’t forget to add some extra nitrogen into the mix. Depending on the material used,
this could be anywhere from 1/4 pound to 1 1/2 pounds of nitrogen per 100 pounds of organic material
added.
Use caution when using peat moss to the mix. The material is very slow to decompose and can drive
soil pH into something akin to a Louisiana bog if used in excess.
When you have completed creating your soil blend, check the drainage. To do that, dig a foot-deep
(30 cm) hole and fill it with water. If the water drains out in about 15 minutes, the drainage is
great. If it takes longer, you need to improve the soil drainage further. If shorter, you may need
to add more organic material to help retain it.
In tight clay soils, consider double digging the bed. This is accomplished by digging out the soil
to a depth of 12 inches (30cm) and placing it off to the side. Then a second 12 inches of soil is dug out
and placed to a separate side. The bottom of the dug out area is improved with organic materials
and/or gravel.
Then the top layer of soil is placed in the bottom of the dug area, and the second layer of soil is placed
on the top of that -- essentially flipping the first two feet of soil. As each layer is reinstalled, be sure
to include soil loosening agents and organic matter.
I've had to do this procedure on many occasion. It ain't fun, but the results are terrific!
By Mark Whitelaw, Kindly Provided by Laura Whitelaw
