Seed-sowing Trick, was Re: Manfreda

Rodger Whitlock
Thu, 22 Jul 2004 13:50:49 PDT
On 18 Jul 04 at 18:41, Floral Architecture wrote:

> ...with my watering practice, seedlings don't make it too far, they
> get washed out of the pots. 

Cultivation trick: top dress all your seed pots with about 1/2" of 
fine water-worn gravel (aka coarse sand) after sowing.

Here in British Columbia, we can get such fine gravel in bags with
very uniform mesh size. It's been labelled at various times
"industrial coarse sand" or "forestry sand" -- used, I understand,
for sandblasting tanks in pulp mills, also for striking cuttings of
conifers. (Don't quote me.)

For some mysterious reason, this stuff has always been easier to
find in Victoria than in Vancouver, even though it comes from a
Vancouver company. Even in Victoria, it's always been tricky to find
a source; some of the bigger hardware stores (not Home Depot to my
knowledge) have carried it among the gardening supplies from time to

It's a very clean water-washed sand or gravel that's been screened
to be very uniform in size. Individual grains are 1/8" in diameter on
average, but of course vary somewhat from that size. Possibly the
manufacturer has a source of natural gravel or sand so uniform that
minimal screening is necessary, but that's only a guess.

The individual grains are not completely rounded; rather, somewhat 
rounded from sharp edged particles, so they have some flat faces.

I doubt the stuff is available elsewhere, so I suggest that everyone
stay in their chairs instead of jumping up and running off a

Industrial coarse sand works very well as a topdressing for seed
pots because it doesn't jump out of the pot when you water; it seems
to consolidate, instead. Yet it's coarse and loose enough that
seedlings have no trouble emerging through it. Crushed-granite
poultry grits do not work at all as well; the grains tend to jump 
around and not consolidate when you flood a pot with water.

I've used "industrial coarse sand" for over 20 years and swear by it.

Those of you who can't buy this product or one similar to it can 
probably homebrew something similar. You need two screens, one with 
mesh slightly coarser than the other, and a source of fairly fine 
gravel as a raw material. I do not know where you can find wire mesh 
in suitable sizes, but if you look around I'm sure you can find some, 
if only because one manufacturer's 1/16" mesh is a slightly different 
size from another manufacturer's. Coarse kitchen sieves and screens 
would also do if the holes are the right size.

Highly recommended.

Rodger Whitlock
Victoria, British Columbia, Canada
Maritime Zone 8, a cool Mediterranean climate

on beautiful Vancouver Island

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