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grit


From: Sheryl Williams <srwillms@gj.net>


>I wasn't able to locate chicken grit (even though I live in a rural area)because
>the supply houses have to buy truck loads of it.  They did sell me a fine calcium
>almost-powder substance that is used instead of egg shells to aid the chickens'
>digestion.  Does anyone know if the calcium could hurt the seedlings?


Karen is correct in that ground oyster shell is not a substitute for
granite grit that we use as a seed topping.  See my article on grit at:
http://www.anet-chi.com/~manytimes/page41.htm
However, the finest grade of granite grit is too large for topping very
fine seeds.  What many growers do is to sow the finest seeds on top
of the grit, then cover the seeds with a very fine layer of white silica sand
to wash them in.

I find that the silica sand definitely forms a crust, once wetted, and is not
the answer for fine seeds, at least not for me.

Oyster shell is sold in my area in three grades, just like grit.  And, the
bags are labeled "grit" and not "calcium supplement".  I am trying the
powder like grade of oyster shell this year, and after sowing 317
packets of seed thus far, I can state with absolute certainty, that it
does not crust, wet or dry.  I use the oyster shell in two ways.  For
larger seeds topped with granite grit, I spread a very very fine layer of
oyster shell for moisture containment.  I find that algae growth is less
that with granite grit alone.  For very fine seeds, or those requiring
light to germinate, I dispense with granite grit altogether, and simply
use a fine layer of oyster shell to both cover the seed and to provide
moisture containment while admitting light.  At this time, I have
thousands of seedlings emerging through oyster shell powder with
no apparent ill effect, and many of those have proceeded through
one or two stages of potting-on, and I find those seedlings to be
normal in every respect.

Does calcium have an effect upon seedlings?  I have not found one.
I have seen some strong admonitions against its use, but I have
not seen any published evidence.  The time that a seedling stays
in a communal pot with oyster shell topping is very short because
they have to be transplanted to individual pots in 2 weeks anyway.

So what is a very very fine layer?  I use a long plastic scoop which
permits the even distribution of a layer that may vary from .02 inches
to .06 inches thick.  That degree of depth control is not possible
with granite grit (starter grade) where each stone is .06 inches
thick or greater to begin with.

I have not used oyster shell for seeds requiring more than 12 months
to germinate, nor for those seeds which are sown outdoors in pots
in plunge beds, nor for ericaceous plants.  On the other hand, I have
had good success with many small seedlings like aruncus, ilex, begonia,
patrinia, heuchera, and buddleia to name a few.  Don't be afraid of
a little calcium for a short time.

manytimes,
tom
zone 5a, NE Illinois, -21ºF Min
http://www.anet-chi.com/~manytimes
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