I don't know exactly what product you are describing when you say
"potting soil". There are pre-packaged soils out there for seed
starting that are light and fluffy; potting soils that are coarse and
have small chucks of wood in them; and then topsoil that is mainly
made out of decomposed organic stuff.

I am assuming that since you described it as getting clogged and
muddy when watered but has a nice consistency coming out of the bag,
then you must be talking about that cheap topsoil stuff that costs
$1.00 per 40 lb. bag.

You could use perlite to fluff it up some, but that might be
expensive to add enough to have a substantial effect. Sand is always
good to help with drainage, but it doesn't decompose or add any
nutrient value to it. Plus, it tends to carry downwards when you
water and settle into a layer at the bottom of the pot--which might
cause it to clog up the pot drainage holes later on.

What I normally do with my own potting plants is: 1) mix topsoil 1/2
and 1/2 with potting soil that has wood chunks in it (like the
moisture control Miracle Grow stuff), 2) add in some slow release
plant food, 3) shake it all up in a big trash bin in order to
thoroughly mix up the contents, and then 4) put it in the pot with the
plant.

If it is mixed right, you should be easily be able to transplant
your plant later on. Just don't water it for a couple of days and the
soil will shrink and stick together into one big cylinder. Afterwards,
turn the pot sideways and gently shake out the entire block--plant and
all. No need to damage the root system by trying to dig it out of the
soil.

Angello

On Sun, 15 Nov 2009 15:02:24 -0800 (PST), Dwight Lassiter
wrote:

This question is applicable to a lot more than edible crops, but I'd
like to understand better about potting soil, whether for starting
plants or for container gardening. I've been using the cheap Lowes
potting soil for a few years. It looks to be largely organic stuff.
That is, it isn't just garden "dirt". OK, so that sounds right. Nice
consistency coming out of the bag. But I notice that this stuff
basically turns into mud after a while. That is, after a long and very
hot summer, when stuff is getting watered every other day to keep it
alive, you dig out a plant, and find that the plant has been trying to
grow in highly compacted and hugely soggy soil. This in a pot with
excellent drainage. Just to get the soil out of the pot, you can't do
it with fingers. You need a trowel to excavate it.

Now, this doesn't seem like the kind of stuff plants would like to be
growing in. I should have realized this was happening, because during
the summer, when I watered, it would sometime pool up in the top of
the pots, and take an hour to drain!! The way I was taught, soil
should absorb water, but be permeable enough to let it soak through.

I found a number of fat worms in it, so it can't be that bad, but ...

OK, my bad, using cheap potting soil. Butt head against wall, etc.

But I still have a few bags of it, and it seems to me that with
appropriate amendments, this stuff could still work. What should I
use? Coarse sand? Perlite? Vermiculite? Compost? Peat moss? Now, if
I'm going to add organic material to it, I'd like it to be stuff that
didn't eventually turn into the organic paste I seem to have ended up
with.