"Ether Jones" wrote in message
oups.com...

You'll have to define "hardpan"..

The area where I want to plant trees has strange soil. The top layer
of about maybe 6" consists mostly of the root zone of the grass.
Immediately below that is about 8" of almost impenetrable hardpan. I
can't dig through it - I have to use a sharp-pointed hand tool to pick
my way through it. Below the hardpan is moist (not wet) clay which
rapidly transitions to mostly coarse sand and rocks. I'm not sure I
understand the proper way to "amend" such soil or how to create a
transition zone.

1) Are you in a "landscaped" development (one of many of the past 5-40
years), where the lay of the land was moved around by bulldozers and
turnapulls, houses built, and then maybe six inches of black dirt dropped on
top?
Just a wild guess, but that is what it sounds like - and the layer of
black dirt and the landscaped clay has formed a barrier (hardpan) on its
top.

2) A transition zone in tree planting is used to prevent hardpan from
forming between the potted soil and the existing soil. It is made by
mixing the two soils together, for six inches to a foot in width or depth,
so a barrier doesn't form at the boundary of the two soils. ( Soil with
compost and the like added usually doesn't set up barriers with the sandy
soils used in pots.)

3) Six inches of soil is about as thin as most trees can use to grow. The
huge conifer forests of the sub arctic are growing on 6-18 inches of soil
sitting on permafrost. It doesn't take much soil for many kinds of trees to
grow well.

4) Since you want to transplant/replant, that hole will need to be at
least pot depth or tree-spade (the big transplant shovel thing) depth for a
transplant.
Given your description of the hole being dug, they might have a hell of a
time punching through your hardpan with a tree spade.

All that said - You always have this trade-off between optimum and enough.
Here, with six inches of topsoil, the roots will fan out in that topsoil and
lay near the top IF the topsoil is ok- but my sense is it will limit it at
some point, especially if it gets dry and a big tree wants that 200 gallons
a day the big ones supposedly use. So how to mitigate that?

Since amending soil is just changing the soil texture and mix so the
roots can get sufficient air, water, and nutrients at the right PH,
(e.g., no organic matter - add compost. Heavy clay - add sand/peat.
Sandy -add clay/peat. Acid - add lime. Alkaline - add acid. etc.)
and given your soil description, and especially if the hardpan was
caused by the developer, I would lean toward just punching fencepost-sized
holes in the artificial hardpan (think power fencepost auger) about every 3
feet or so in a 20- 30 foot diameter circle around the new tree spot (that
diameter is roughly the edge of a bigger tree's root line), fill them back
up, and let nature take its course in the tree breaking up the hardpan.
If there is nutrient slowly going through the hardpan at those holes, so
will the roots, and the tree will make its own depth.

The thin weeds and the adding of limestone and leaves and then growth is
interesting. A soil test for PH is in order.


I can't imagine how anything could grow there but it does. Five years
ago there was nothing there but thin grass and weeds. Then I stopped
mowing it, and now there are sassafras, black cherry, black locust, and
maple trees growing there, all wild. One of the black cherries is
over 6' tall. A couple of the sassafras are over 7' tall. One of the
black locusts is over 12' tall. The maples appeared later and most are
less than a foot, but there is one that is about 5' tall, and thriving.

Two years ago I bought a 5' "autumn blaze" maple at the local
mega-mart and planted it in this area. Not having the least idea what
I was doing, I dug a deep (not wide) hole and backfilled it with dead
leaves and other organic matter gathered from the woods, and stomped it
down. I set the tree on top of that and threw in a bag of "garden
soil". When I was done, the tree's root flare was about 8" below the
surrounding surface, so I filled the rest of the hole with crushed
limestone to make it level. This little maple has been growing like a
weed ever since. This spring it's going nuts, putting out new growth
everywhere at an amazing pace. Every couple of days it seems there's
another set of leaves opening up at the tips of the branches.

Most "perennial" plantings do shoot up the second year - and it is too soon
to know if it will be potbound by the hole.
The tree is using what it took in last year and stored in the roots to
make the new shoots- probably before the limestone got to change the soil
below it. That limestone is normally bad for trees - a ph test really is in
order.

Wild maple have the same growing needs and habits as the ones you buy at the
store, unless the bought one is pushing the zone or a fussy variety.


Now
that I'm learning a bit more about what trees need and how they should
be planted, I'm wondering if this little guy is in for a rude awakening
when he discovers he is in a tiny little oasis in the middle of the
sahara dessert. Where will his roots grow? Under the hardpan? Is
this viable? Should I dig him up this fall and re-plant using a more
proper method?

Trade-off between damage done to roots transplanting, and poor growth from
leaving it. You can't tell yet if it will do ok in the next few years...

And, how do the other trees (the wild ones mentioned
previously) deal with this?

They take off from seed, needing little to get going -- and if they can't
make it when they are young seedlings/saplings, they are smothered and die
and another species gets the spot. Usually, only if you pay for the tree
with money or time do you notice the process.


I'm at the point in my life where I find all this gardening stuff
fascinating. There's so much to learn. I've never really paid much
attention to it before.

I had to laugh when you mentioned renting a jackhammer. That very same
thought had just occurred to me last week. About three years ago I
had a guy over here with a Kubota with a backhoe to dig a 10-foot
trench to bury some drainage pipe. He had a tough time breaking
through the hardpan. He had to strap the back end of the machine to a
hickory tree to get enough traction to get the bucket to break through.

In your earlier post you mentioned "sun splits" and that reminded me of
something. I think that happened about 2 years ago to the maple I am
considering moving. There was a vertical split, about 7 inches long,
along the main trunk, about 2 feet from the ground. I can't remember
what time of year I first noticed it. Being concerned about insect
infestation, and being largely ignorant about such matters, I sprayed
the split with an insecticide containing permethrin. The following
year, the two lower branches on that side of the tree died.
Coincidence?

Given what we spray on trees to kill scale and feed in the roots as
systemics, it was probably insects and the split more than permethrin.

Or direct result of my spraying? At any rate, the split
has now healed over, and the tree appears quite vigorous this year,
with a lush set of leaves. Inspired by your earlier post, I went out
this afternoon and did a little pruning. Just removed some small limbs
that were growing at the wrong angle and threatening to choke or get
choked by other more desirable limbs. Still too timid to be doing any
major surgery. I'll have to work up to that.