gethyllis cold tolerance (Rick Buell)

Tim Eck teck11@embarqmail.com
Fri, 23 Jan 2015 08:19:44 PST
It's interesting and somewhat counterintuitive that this boundary effect is
nowhere near as strong and the drainage much better if you put the coarse
material on top of the fine material - probably similar to the 'brazil nut
effect'.
$.02
Tim


-----Original Message-----
From: pbs [mailto:pbs-bounces@lists.ibiblio.org] On Behalf Of Tim Eck
Sent: Friday, January 23, 2015 9:37 AM
To: 'Pacific Bulb Society'
Subject: Re: [pbs] gethyllis cold tolerance (Rick Buell)

One way to envision this boundary effect:
If you have identically sized spheres their closest packing is about 74%,
leaving about 26% voids.  If you then place much smaller spheres in contact
(think gravel and sand), the sand will infiltrate the gravel voids, taking
up 74% of this 26% =19%.  So, now the contact zone is 93% solid and 7% void.

Tim


-----Original Message-----
From: pbs [mailto:pbs-bounces@lists.ibiblio.org] On Behalf Of Alberto
Sent: Friday, January 23, 2015 8:51 AM
To: Pacific Bulb Society
Subject: Re: [pbs] gethyllis cold tolerance (Rick Buell)

Putting ingredients of  a potting mix in layers slow down drainage instead
of improving it. This has been researched for long. Water will percolate by
gravity through a layer but when reaching the next it will collect making
the mix stay wet for longer than planned through capillarity. This s the
reason why the best potting mixes are a combination of not water retaining
materials, so excess water is rapidly forced out. 

 





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