We had a local landscape company help us design and prepare some
garden beds. Around here we have almost entirely red clay soil. The
consultant arranged to have 2-3 inches of topsoil and leaf mold put on
top of the new beds. I asked him about the need to work it in. He
said that he's be wasting my money if he were to try to roto-till it
in. And that as I planted the ammendments would work themselves in
and also eventually leach down into the existing clay soil. When I
plant perrenials I'm trying to mix the ammendments in as much as
possible, but I also worry that the clay around the hole will still
keep rainwater around the roots and rot my plants.
Also, we want to put down lanscape fabric (over the ammendments but
under the mulch), but will this keep mulch and other organic matter
from eventually mixing with the soil? How about preventing plants
like daylillies or back-eyed susans from propagating?
Thanks in advance!
There is so much debate about this - some say that if you work all the
amendments in, all you have done is create a concrete trough on the
sides. Some say work it down 12-18" and you'll be above the "water line"
of the clay. Some say berm it up and put down a ton of topsoil over the
clay. Some say dig the red clay OUT, dispose of it and put in good
topsoil. That last one sounds like real trouble to me.
You'll get lots of conflicting opinions on this.
I dunno - I just prepared a new bed for bulbs and dug through this heavy
red clay. I added about 200 lbs of compost and worked it in to about
12". It is very hard stuff to work (the clay). I stand on the spading
fork, wiggle from side to side, and then lean back of the fork to pull
up a boulder of clay. Then I take a gizmo known as a "hoe matic" - a
hand held tool looks like an ax blade turned sideways - and break up the
clay to small pieces. After all has been broken up, I add amendments and
mix well. Let this sit for a couple of weeks and then plant.
When the clay is so hard, you can't even use a tiller. It's like going
Every flower bed at my house was done this way. AND every year I have to
add amendments to keep the soil in good shape. That d**n clay pushs up
from the center of the earth.
But my flowers are beautiful!! And every spring is a delight!
Clay soil does not necessarily translate to poor drainage and most plants
will grow happily and well in clay as long as the drainage is reasonable. I
wouldn't worry too much about the perennials. For the most part, they are
smaller plants initially so no need to dig a large planting hole and the
roots will be able to spread relatively easily into the unamended soil. For
larger plants (trees and shrubs), dig wide and shallow planting holes and
plant high (top of root ball above the soil surface), mulching up in a mound
to cover any exposed portions. This will greatly reduce the "bathtub" effect
of digging a deep planting hole into less than ideally draining soil. And
you do want to avoid amending planting holes, specially in clay soils - the
difference in sol textures of the amended vs. the non-amended soils will
create more drainage and water penetration problems than it will help.
Avoid using landscape fabric under the mulch - it is a waste of time and
money and can be detrimental to your intent to lighten your heavy soils. It
is not very effective at supressing weeds, makes it difficult to divide or
transplant, and will prevent your mulch from breaking down, migrating into
and improving the existing soil. A good thick layer of organic mulch -
leaves, composted manure, garden compost, pine straw - will be just as
effective at weed supression and will enrich and improve the texture of your
soil over time
pam - gardengal
You should be fine with the amendments added on top of the clay soil. I own
a flower planting service here in Raleigh, NC and will add amendments on top
of our red clay to plant flowers. It does work its way down and with each
planting season, I add more of the leaf mulch. I usually get a large load
of leaf mulch from our local waste center and plant directly into it. It
basically is compost that is breaking down and feeding the plants at the
I wouldn't bother with the landscape fabric and just concentrate on putting
4-5" of leaf mulch which will help in retaining moisture while keeping weeds
at bay and feeding the plants. Your black-eyed susans should definitely be
able to seed into the mulch for more plants. I mulched all my perennial
beds with the leaf mulch and mine multiply like crazy. I just dig them up
and move them in the spring.
Hope this helps with your gardening endeavors.
Flowers By The Yard
Depending on where you are, soil amendments will break down at different
rates. If you are in the south or deep south, the heat, humidity, and rain
create ideal conditions for the breakdown of organic materials. So just
piling this kind of stuff on top of your beds is fine - it will break down
quickly, the worms will pull some of it down into the clay, and plant roots
will follow those worm holes into the clay right along with it. Of course,
this also means that you have to replenish that kind of mulch frequently. On
the other hand, organic materials in cool/cold climates, especially ones
that are dry in summer break down much more slowly. When I lived in north
Florida, I had a gardener friend come to visit me in February. I had raked
all the deciduous tree leaves into large piles around the bases of all my
trees. (I had a grove of wild black cherry trees and native persimmons). He
was all set to put all the leaves into bags and haul them away. I said, "no,
the leaves will all be gone by the end of April". He didn't believe me,
until I took pictures that April to to prove it to him. Where he lives (the
inland Northwest) a pile of maple leaves piled around the base of a tree
would still be there, just shrunk a little bit and a touch darker, one year
I have read some of the answers you have got and I agree with some of them
but not all. If you want to improve drainage to your soil and in long term
the overall structure of your soil, you should add as much coarse organic
material as you can and work it in every year. The topsoil amendment will
not do much to the texture of the clay soil. You shouldalso add plenty of
lime as this also will add to improve your soil.
I think perhaps you mean you can change the overall "texture" of the soil,
rather than "structure". Soil texture can be changed by adding organic
matter or other soil amendments - soil structure refers to the form of the
particles which comprise the indigenous soil and is virtually impossible to
alter except by compaction or excessive tillage.
It is not necessary to work in organic matter to improve soil texture. The
action of the soil organisms, the decomposition process and even the
miniscule pulling action performed by plant roots will serve to eventually
work any soil additions well down under the soil surface.
Lime does nothing to "improve" soil other than to reduce pH or sweeten
acidic soils and provide slight amounts of calcium and magnesium. This would
not be a typical soil amendment unless soils were excessively acidic (less
than 5.0) or you were attempting to grow specific plants requiring more
neutral or alkaline conditions. Soil tests should be performed before
applying lime in quantity.
Gotta ask about this... I have heavy red clay soil AND I have a deep
rich forest behind the house with tons of leaves left on the ground
every year, for at least 30 years. Lots of trees and bushes. If I dig
down out there over 4", I hit solid red clay.
By your reasoning, after all the years, I would have black dirt.
This red clay is the bane of every gardener around here. If this worked
as it obviously does in your area, it does not work here. I just cleared
out an area under the trees and this stuff is so dense, you could cut it
with a clay wire (like potters do).
I don't think one size fits all...
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