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Re: John Innes seed compost

Janet

"Sharp" sand FEELS sharp between the fingers: the particles under 
magnification are very angular.  In general, the sharpest sand comes 
either from decomposing granite or sandstone, or from high-gradient 
[mountain] streams.  Wind-blown sand from sea-beaches or dunes is usually 
composed of rounded grains.  

If you're making a loam-based potting or seed compost, the bagged 
builders' sand is probably OK.  For really fussy alpines, the presence of 
fines [silt, clay] is a concern.  Bagged sands will generally be clean, 
but bulk sand from landscape dealers or gravel operations may be washed 
through window screening to remove the silt.

Play sand is rounded [ie, beach] sand, or I think in some cases is gypsum 
rather than quartz sand, in any case not suitable for general 
horticultural use.  "Sacrete" is bagged, pre-mixed concrete [just add 
water] -- it would have interesting consequences if used in a potting 
mix!

Loren Russell, Corvallis, Oregon

 On Sun, 15 Jun 1997, Janet Nancy Yang wrote:

> Exactly how fine are "sharp sand" and "silver sand"? 
> Around here I can buy mason's sand, sand for a child's sandbox, 
> builder's sand (coarser than mason's sand), and Sakrete (don't know 
> where that fits in). Which of these are sharp, and which are silver?
> 
> Janet
> 
>
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