enigma wrote:
"Natty Dread" wrote in
:

My house was built two years ago on land that was
essentially a vacant lot for 15 years. The soil is really
poor quality - hard-packed clay with little pebbles mixed
in that I can barely break up with a shovel. I haven't
been successful at getting a lawn to take consistent root,
so I've decided to have most of the front lawn area
replaced with a series of interconnecting planting beds
around the fence line to minimize the grassy area. The
landscaper is going to rototill the soil down about 18
inches and add some stuff to improve the quality and make
it easier to work. He says there are two basic options:
Replace the soil with a high-quality topsoil, or till in
amendments to the existing soil. I prefer leaf compost for
the organic benefits, but he recommends gypsum instead
because he says the gypsum will start to break down the
clay pretty much immediately and add some acid to the soil.
It's a big area - the lawn is probably 30x50 - and he's
going to cut in perimeter beds around the border about 8
feet wide, so cost is a factor in my decision. What do you
all think of either of these options? Any other ideas
would be appreciated as well.

i'd mix in both the composted leaves and the gypsum. your
landscaper is correct that the gypsum will help with breaking
down the clay soil, but adding composted material will also
improve the porosity & water retentive qualities right away.
are you sure you want 8 foot wide beds? are there going to be
paths to get into the beds without compressing the soil around
your plantings? i just don't like beds wider than i can reach
into easily for weeding & pruning... and that's about 4 feet
wide.
lee

I agree, add both.

You want to work as much as possible with the native soil because some
plants will try to send their roots down below any portion that has been
tilled. If you import topsoil, there will be an interface between it
and the soil below. Often, roots will not grow past such an interface,
leaving you with shallow-rooted plants that are easily stressed in hot
dry weather. If you improve the native soil, however, there will be
more of a transition and less of a sharp interface.

This is one reason why planting bare-root roses and fruit trees gives
better results than planting them from containers. You might also get
better results seeding a lawn instead of sodding. The roots are in
direct contact with native soil (albeit improved) and not trapped in a
soil very unlike the native soil.

--
David E. Ross
Climate: California Mediterranean
Sunset Zone: 21 -- interior Santa Monica Mountains with some ocean
influence (USDA 10a, very close to Sunset Zone 19)
Gardening pages at http://www.rossde.com/garden/