VX wrote:
On Sun, 29 May 2005 19:19:21 +0000, Mike Lyle wrote
(in message ):

spakker wrote:
I have got into gardening over the last two years. I am planning
some
re-building work and have put most of my plants into pots-upto
dustbin size. However I used B&Q type compost rather than garden
soil-some black soil but all based on heavy clay-to avoid
weeds.One
or two years down the line many plants are suffering.I know
watering
is more required for pots , but I am begining to suspect that the
bought -in compost is not really upto the job. Any comments
please.

The compost's probably exhausted: the nutrients they put in it
don't
last long, and the compost itself won't have any food value. If
you
start giving a regular liquid feed (Phostrogen or B&Q's own brand,
whatever's cheap), just follow the instructions on the packet and
your plants should perk up. As you say, plants in containers do
need
regular watering.

snip

Any recommendations for the best compost type for garden plants
when
grown (outdoors) in containers? Should they be potted in a
peat-type
compost, a loam-type compost or in sterile topsoil? And is there
any
real difference between the last two?

I still don't really understand the differences between the
peat-type
and the loam-type. I've read that the latter holds water
better/longer and so plants don't need so much water, but I don't
get
the other differences, such as which type holds nutrients longer,
or
what other advantages/disadvantages they have.

I'm for the loam type. They don't hold as much water as peat or
compost-based ones, but they're easier to wet, which more than makes
up for it. They have a few trace elements which the others lack; but
still need to have regular feeds of liquid manure or the stuff out of
a packet.

If you've got some nice topsoil, it'll probably be fine; but it's
very very variable. I'd tend to mix it with some peat or compost for
water-retention. Guesswork has always served me well enough, but I
suppose one peaty stuff to two of topsoil would be near enough for
jazz. If you've got any grit, sling in a bit of that, too: maybe half
as much as the peat. If the soil's got a lot of grit in it already,
let's say three soil to one peat. This barbaric approximation isn't
at all unlike John Innes mixture. Do it your own way: the plants
won't mind. You can get fussy when you've built up some more
experience and feel ready to take on some more ticklish plants.

--
Mike.