Re: The Innes potting mixes and alternatives.
Joe Seals wrote:
>
> Michael, et. al.:
>
> Here's an interesting timeline...
>
> The John Innes Horticultural Institute in England
> developed their first mixes in 1939.
>
> Not even a handful of years later (1941), the
> University of California started developing their "UC
> System" of mixes.
>
> They did their work because the original John Innes
> mixes were difficult to reproduce (the "loam" was an
> English specialty), the sterilizing process led to
> some dangerous residues, the mix was heavy, and labor
> was intensive.
>
> The "UC Mixes" were various ratios of fine sand and
> peat moss with a number of fertilizer variations.
>
> This "system" "hit the market" in the 1950's and is
> still used by many large-size container plant growers,
> particularly in California.
>
> Then in the 1960s, the good people at Cornell
> University introduced Peat-Lite mixes with half peat
> moss and half vermiculite or perlite, along with lime,
> nutrients, and wetting agents.
>
> For the bedding plant, small pot plant, and "color"
> industry, the Cornell mixes are the formulas of
> choice.
>
> What I've found in my many years in the commercial
> plant industries, is that the big guys almost always
> use these big time formulas. The little guys, who
> grow barely 20% of the plants produced but who
> represent 70% of the growing companies, almost always
> develop their own "custom" mixes that frequently have
> nothing to do with ANY of the professional formulae.
Just a few comments from a rank amateur.
I have an interesting little book which i bought in 1953. the third
edition (dating from'45) of Seed and Potting Composts by two members of
the John Innis Institute
W Lawrence (who did the science I think) And J Newell who did the donkey
work.
Between them the designed and refined the basic JI mix which as far as I
know hasn't changed appreciably since.
Two points, first, the "loam" they used was specifically turf loam, a
product made by piling up turves until fully composted, so it was rich
in OM from the digested grass.
And second, the recommendations for the additional lime and
superphosphate related to the normal nutrient status of that particular
loam, which was somewhat deficient in both calcium and phosphate. No
doubt these would need adjusting for different materials and especially
if growing Ericaceae..
The JI base added to the potting composts was apparently the best which
could be devised at the time to provide on-going nutrients. I guess now
one could conveniently substitute a long-term slow-release preparation.
I must say hoof and horn meal has never come my way and I wonder if it
is available any more.
Regarding the American mixes, commercial potting here is obviously done
with something similar, though I understand local formulae often
include ground pine bark. I realize these are highly advantageous to
large operators being so easily atandardized and light to handle, but
for the home user they have a number of negative aspects. Perhaps the
worst is that they dry out pretty easily and (due I suppose to the peat
component) are very difficult to rewet without full soaking. The fact
that they have no intrinsic fertility but depend entirely on added
nutrients means that if one keeps a plant more then about two or three
months extra food becomes essential. Personally if I get any plant
growing in such a mix I repot it as soon as possible.
One other grumble is that they are altogether physically too light if
used outdoors in our windy climate and the pots very liable to blow
over.
I myself used the JI mixes and a number of varients for many years, but
about four or five years ago for potting and growing on I shifted
entirely to a mix which I got from Organic Gardening magazine consisting
essentially of my own finished compost (unsterilized) mixed with
approximately one third of sharp sand.
Over time this has evolved to also include seaweed powder for trace
elements and some ground rock powder for general minerals. Any extra
nitrogen required is given in the form of liquid feeds (mainly fish
extracts). I do not add any lime as compost tends to be naturally
buffered to a pH of around 6.5 which suits most of the plants I grow. My
compost is not entirely devoid of weeds, but it is small matter to
remove these as they appear.
I do not use any peat nowadays. Even without ecological considerations I
have no love for this material which seems to raise more problems than
it solves. I did try substituting ground coconut fibre, but found it
seemed to slow growth quite noticeably. I do not know exactly what the
problem was, but I have seen it stated that some samples have a high
salt content, which could have been what was wrong with the stuff I
tried. Neither vermiculite nor perlite is readily available in this
country and are anyway expensive because imported.
In fact compost itself naturally has a good water-holding capacity and I
found that coarsely-ground pumice substituted for half the sand
component contributed to both water-retention and free drainage.
(Pumice, locally easily obtainable is a foamed silicate rock produced in
some volcanic eruptions (there are hundreds of square miles in the
centre of our Noth Island simply covered with it))
And for seed raising I use home-made leafmould (also unsterilized) made
from a variety of deciduous leaves (mainly oak, elm and maple)mixed with
an equal amount of the same sand. The young seedlings are watered about
three time a week with a weak solution of seaweed extract.
You may wonder if the lack of sterilization is any problem. In fact the
organisms present seem to be able to keep the "baddies" under control
and I have never had any trouble with damping-off or root rots since I
started to use these mixes. For very delicate seeds particularly
Ericaceae one can add some ground sphagnum moss (live moss not peat)
for added protection.
Another bonus is the relative freedom from soil pests. Before I started
to use these mixes root mealybug was always turning up in my greenhouse,
but since cleaning the plants and transferring them to compost I have
never seen another
case.
I find that most plants will go on happily with no extra feeding for at
least six months, but for large plants especially outdoors I fortify the
mix with clean live soil from my vegetable garden and also add a
slow-release preparation called Magamp which lasts up to two years
without replenishment.
So there is another viable alternative for anybody who prefers to do
their gardening as naturally as possible.
Moira
--
Tony & Moira Ryan <theryans@xtra.co.nz>
Wainuiomata (near Wellington, capital city of New Zealand)
