Best soil for a raised bed?

Mon, 21 Jul 2014 09:17:15 PDT
>The above motivations explain the behavior of roots in plastic pots versus
>clay (or fabric) pots.  Plastic pots are prone to 'spin', where the roots
>will circumnavigate the lower periphery of the pot several times, seeing 
>impervious plastic as a rock.  (Earthenware) clay pots and fabric pots 
>also generate this behavior except that their periphery wicks and 
>moisture, removing the moisture gradient motivation.  Non-porous stoneware
>pots will also exhibit spin as will a transition from a porous potting
>medium to a denser clay hole where the dense clay will resemble a rock to
>the growing tip.

Excellent. Explains a great deal.

>Chestnut trees planted with potting soil intact would circle the hole with
>their roots several times until a dry spell killed them.  Now we know to
>plant everything bare root.

I lost almost everything grown in plastic containers, until I employed a 
process I call "degunkification", which I ought to trade mark, involving 
removal of all the soil-less mix in the root ball (peat is the bane of my 
gardening life), and then gently pulling apart the circling roots with a 
bonsai-style root hook, before planting.
I turned 63 last week, have been gardening since the 1950s, and am still 
learning. Mostly that what I thought I knew was all wrong.

>It's worth noting that the 'porosity' is greatest -up to 50% - when
>the particle size is all the same.  Although absolute size of the aggregate
>doesn't enter into the calculation, it will determine the ratio of 'air
>porosity' to 'water porosity' with larger aggregate favoring air porosity.
>Depending on your pH requirements you may want to look at 'sand bed'
>aggregate from a local quarry since it is washed of dust and fines to
>promote optimum porosity.

My sand piles are half pea gravel and half "builder's sand". I have noticed 
that oncocyclus planted in these beds go dormant when not irrigated (now), 
but stay green and growing in the one bed which receives irrigation because 
there are other new plants in the sand pile.
I have a squirt gun (my weapon of choice, mostly used against rodents) to 
deal with visitors who talk about "drainage".

Bob Nold
Denver, Colorado, USA 

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