On 8/9/12 4:34 PM, David Hare-Scott wrote:
David E. Ross wrote:
On 8/8/12 10:12 PM, David Hare-Scott wrote:
David E. Ross wrote:
On 8/8/12 2:02 PM, mdemetri2 wrote:
Hi, I have been 4 years in my current home, and the back garden
pretty much each year needs some new plants and shrubs. Although I
admit we have in the past bought what looks nice and arent
necessarily suited for our east facing heavy clay moisture
retaining soil.

Firstly, I have over the last 2 months or so being contemplating
removing the soil/clay from our flower bed about a foot or so and
replacing with new soil mixed in with sand but adding more depth -
so allowing for a total of 15 inches of decent soil to replace the
harsh stuff we have now. Lots of digging out and
replacing.....good idea?

What you propose will create an interface between top soil and
subsoil. Many plant roots will not cross that interface.


OK but it is a flower garden this may not be a problem.

D


At the end of the original message, mdemetri2 mentioned planting
shrubs and perennials. For those, this would indeed be a problem.

How are you going to remove the barrier 15in or more down, how deep does the
clay have to be amended, how will you know when you have done it and how
long will that take? Maybe the answer instead is not to use deep rooted
plants or to build up mounds several feet high.

D


If the clay is treated with gypsum to make it more porous and if the top
foot of clay is tilled with new top soil, the interface between the top
soil and the clay subsoil will be blurred. Clay is often rich in
nutrients other than nitrogen. With careful use of fertilizer and with
infrequent but deep watering, plant roots will grow down below that
blurred interface into the clay.

My natural soil is heavy adobe clay. What I have suggested here is
based on my experience, especially my use of gypsum. Every year, I use
at least 50 pounds (23 kg) of gypsum in my garden; some years, I use 150
pounds (70 kg). Other than the obstructions caused by tree roots, I can
dig the soil quite easily; and my plants -- all perennials, shrubs, and
trees -- seem to thrive.

No, I do not have a large garden. My total lot is slightly less than
0.25 acre (0.1 hectare), including the footprint of my house and the
extreme slope that I describe at
http://www.rossde.com/garden/garden_back.html#hill.

--
David E. Ross
Climate: California Mediterranean, see
http://www.rossde.com/garden/climate.html
Gardening diary at http://www.rossde.com/garden/diary