Shiva said:

Roland ...wrote:
I am not alone in thinking that clay is good. Let me provide the opinion
of several Rose authorities:
snips IMPRESSIVE list of other people who love clay
Very nice. I still disagree.

I too disagree. And here are some of my arguements:

First and biggest: most clay minerals cause a chemical reaction
that 'locks up' iron in the soil. That is, it makes it unavailable
for plant use. Regular amendments of iron are needed for good plant
health in these soils. New growth appearing on the rose bush that is
light yellow green or whitish is an indication of lack of iron.

Second: Clay soils are usually alkaline with a pH of 7 or above.
Roses thrive in a slightly acid soil of pH 6.5. Therefore acid
inducing is necessary. This is usually accomplished in these soils
with the addition of decomposing plant material such as compost or
horse manure or even top mulch.

Third: High percentage clay soils have poor drainage. In areas with
a lot of rain, this leads to occasional standing water, something that
quickly becomes deadly for rose roots, and at the least leads to poor
root health.

Fourth: Clay soils are dense and easily compacted which keeps air
from moving down into the soil. This slows the natural process of
composting of whatever organic matter is present in the soil. People
with heavy clay soils need to dig with a digging fork and aerate the
soil around their roses in order for them to perform well. Or add a
lot of worms..... grin

In summary: All of these problems can be dealt with, but it takes
extra effort than that required for loamy soil with a high (60
percent) level of decomposing organic matter.

It is possible to grow good roses in high percentage clay soils, but
you have to amend on a regular basis. Since most people don't know
this or do it, they would tend to see roses grown in these soils
perform less well than roses grown in 'better' soils.

My soil is a river floodplain in the bottom of an old lake bed, and
therefore very high in clay. In order to grow roses well in my soil,
I dig a hole about 20 inches in diameter and 20 inches deep, toss the
clay, and fill the hole with 2 cubic feet of 'EarthGro' brand Potting
Soil bought from Home Depot for $3.96 a bag.

Since I started doing this, my roses have thrived. Roses still
growing in my older beds with high percentage clay soils do noticeably
less well even though the soil around these plants is top amended
regularly.

When you look at the big picture of how much you really spend on each
rose bush, an extra 4 bucks is really worth the value that it gives
in the long run.

By the way, I learned the above technique from an assortment of great
and impressive Rose Authorities as well, right here on rgr several
years ago.

Bob Bauer
The voice of experience...... heh heh

Zone 6 in Salt Lake City
http://www.rose-roses.com/