Re: Improving the Soil--a BUNCH of questions!

Well, Cindy....no hort. ed. here, either, just  30 years observation
of a plain 'dirt' gardener, so FWIW...some observations....

Paul described the basic differences in root systems between woody &
herbaceous plants, which, along with the need to divide and renew a
lot of the perennials we grow, is why you need to leave shrubs alone.
 Some perennials go for many years without needing renewal division -
think of Peonies; some clumps outlast the gardener.  Others, because
of the way they grow, need continual dividing to remain vigorous -
think of Heuchera.  I think it's more to do with the plant's natural
growth habits than whether it's "new" or not to cultivation or native
or exotic to our particular area.

Some are very heavy feeders and exhaust the soil around them in a few
years, so need renewed soil to flourish.  Others are not & don't need
much beyond chopped leaves as a mulch forever.

In my experience, all perennials (except those that require a very
lean soil to start with) do better in my particular brand of clay
soil if it is deeply amended to start - opens it up and provides more
root run.

I agree with Paul that providing this via raised beds is sure easier
than double digging!  I have, however, created a lot of 'topsoil'
from pure subsoil and huge quantities of organic material over the
years via the double digging method.  Once I do that, I never do it
again for that particular bed, but just mulch and top dress (if the
plants are lucky); when I plant something new or dig & divide, I
amend the top spit as far around the work area as practical.

Even if you double dig & create a bed you can dig with your bare
hands, you will find that the soil re-acquires the original
consistency over the years if you don't do it again.  However, tilth
is always better than it was originally.  Even soil in raised beds
tends to pack down after a few years if it's clay based to start
with.  I have no experience of sandy type soils.  Silty soil can turn
into concrete with the action of rain after a few years, if it isn't
mulched.  All depends on the original basic composition of the soil.

Probably most of the shrubs and trees that we plant in our gardens
are not native to our particular area & may have somewhat different
requirements from native plants who have adapted to the soils we
have.  They all have pretty wide-ranging, relatively shallow feeder
roots &, as Paul says, take a while to recover from root damage.  You
can't really dig over soil around woody plants without doing damage
to their root systems.

Current thinking is that one should not amend soil when planting
woody plants, just loosen it in as wide an area around the root ball
as possible, to the depth of the root ball.  I tend to not agree
entirely, depending on the particular plant in question.  Some I know
I can just plop in and water & they will grow away; some I know I
need to provide better or somewhat different soil than what Ma Nature
has provided (rhodies, for instance abhor heavy clay soil).  I do
agree that amending soil for woodies needs to be done in a wide area
& not just in a hole just a bit larger than the root ball...this is
particularly true in clay soil.

I think, that like most gardening issues, there is no 'right' or
'wrong' way to plant (as long as you plant roots heading down and
tops up).  You have to know what your soil is like & what the
particular plant you are planting requires.  Then you can do the
necessary & will know when you absolutely need to spend time mucking
around with dividing, amending, etc. & when you can plant & let them
get on with it.  Learning your soil takes a few years of working it.
Some plants need a lot more TLC than others. Your plants will tell
you.  If they grow away madly & look healthy, they are happy with
what they are planted in.  If they don't perform well, they are not &
something should be done if you want them to be happy.

If you keep a continual moist organic mulch going, earthworms will
come...even if there are none to start with.  They will burrow & pull
the organic material into their burrows to eat it & then deposit
their castings...this helps aerate clay soil & moves some organic
material into it.  However, this doesn't move much nor very far.

If you dig in the woods, where leaves have fallen & rotted for years,
 you will find that the layer of dark, organic soil is pretty
shallow; you soon hit mineral soil with little organic material in
it.  Same happens in the garden.  The organic layer is fairly shallow
(saving those incredible deep black Mid-West soils) unless you deepen
it by digging in a *lot* of organic material & then maintain a
mulch...this increases the area that soil critters work in because
most of them are working at decomposing organic material into
substances that can be absorbed by plant roots....thus "feeding" the
plants....so the more organic material, the more soil critters and
the better fed the plants are (in *very* simplistic terms).  Since
organic material is coarse in texture, it also allows more air
pockets in fine textured soil for the oxygen that plant roots need to
function.

Plants obtain needed minerals from subsoil & will send roots down
into it, but will have most of their roots in the top layers of soil.
 This is true for trees and woodies & shallow rooted perennials.
Deep or tap rooted perennials can send roots down into subsoil a
surprisingly long way...think of poke weed or dandelions!  Fine
rooted perennials need looser soil to grow a good root system.  The
health & vigor of a plant's roots is what determines whether it will
perform well or not.

Most Hostas will survive in the most incredibly lousy conditions, but
if you really want to see them strut their stuff, you need to give
them good, organic soil...so dig up your clump and amend away:-)

Marge Talt, zone 7 Maryland
mtalt@clark.net
Editor:  Gardening in Shade
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From: Cindy Johnson

Would you, and others too, address the subject of re-working
perennial borders vs shrub borders?  (since I like to mix my shrubs,
trees, and perennials).  Why do perennial beds need to be re-worked
over the years, and shrub borders don't?  Or is it more a matter of
they "like" it, not "need" it???  (I have to ask that of myself all
the time too!!!)  Would both shrubs and perennials benefit from
re-worked soil, but it's not feasible with shrubs because of their
size? Since someone is not digging up and re-working soil in the
wild, should we do it just so they'll grow better in our gardens,
than they would in the wild?  Or are some of our new perennials just
so different than their wild relatives that they can't flourish
without this intervention anymore?  But wouldn't that also be true of
the new varieties of shrubs?  Or is there some basic difference in
their makeup that comes into play here (like woody vs soft tissue??)

If we just add organic matter on top, won't that be worked down into
the soil by the organisms that live in it?  That sure seems alot
easier.  But having said that, I have a 5 year old clump of Hosta
'Sun Power' that should be alot bigger by now.  I planted it near the
garage and I've decided to dig it up and amend that soil and replant,
to see if that helps.  It is one of my 1st hostas I ever planted, and
it's likely that I just dug a small hole, in poor soil used to
backfill the foundation, and plopped it in.
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