plant mixes/Amaryllis belladonna

Hamish Sloan
Sat, 30 Jul 2005 13:09:54 PDT
-----Original Message-----
From:	Mary Sue Ittner

"Many years ago I had my husband buy me some decomposed granite after
everyone raved about it. He got the kind with fines. I think it weighed
more than sand so using it made the pots very heavy and it kind of clumped
together so it didn't seem to me that there would be much air in the mix at 

The clumping suggests that there is some surface active agent present in 
granite that makes it "sticky". There are similar agents in any clay-based 
loam that have the effect of giving lumps when it gets wet that dry out 
with difficulty and when it is dry, wetting the soil/compost/whatever is 
difficult. It reminds me  of the story about the planning for the first 
canals in the UK. There were fears that widespread flooding would occur. 
Someone had to demonstrate to the assembled members of Parliament that 
while dry clay allows water to pass unhindered, "puddled clay" would hold 
water and "puddling" was the way to line the canals so that there would be 
little or no water seepage. Dry peat is also difficult to wet, but once it 
is wet, no problem.

As I have a clay-based loam, I have given up on adding grit for similar 
When compaction occurs, the clay particles sticking to the grit block any 
air flow by filling possible pores. Smaller amount of loam? - it just goes 
down to the bottom of the container, leaving the upper layer(s) nicely 
porous and a nice example of Alberto's poor drainage. I remember two 
examples of bulbs given to me that were doing badly for just this sludgy 
bottom problem - an ammocharis coranica and a crinum of species unknown.

What is needed is porosity. This is why the baked clay granules idea has 
been tried. Perlite is another possibility. Some of you are fortunate to 
have access to pumice supplies. Organic agents for porosity often used, 
hence peat (though some environmental cost here), leafmold (I've now got 
into a routine to produce enough of my own leafmold for pot work so that I 
don't use peat), coir (There is a cost factor here. I have been able to 
shred two old coir doormats which produced as much coir as a ?5 - about $10 
- block of coir at the local garden centres. The cost of the replacement 
doormats was less than the coir block! Someone is making big profits here 
on the back of people's environmental concerns. In addition, the coir block 
is dusty - too fine; my shredding gave fibres in the range half-an-inch to 
two inches.)

"Last year I heard a talk from a man who grows carnivorous plants and he
said coir was death to his plants because of the high salt content. ...
One year I used mushroom compost in my mix when I ran
out of other things and that was a disaster. And I haven't been happy with
mixes containing some of the baked clay products that others have liked so

Salts present can be another problem. I know nothing of salts in coir. The 
compost used for mushroom growing beds are usually covered in a layer of 
ground chalk or limestone - you will need a fairly acid soil to neutralise 
that lot! Mary Sue's comment suggests something more than just lime.  Also, 
the mushroom compost will be treated to kill off the fungus gnats - nothing 
like a few wormy holes to put you off mushrooms - and various other bugs in 
the precursor horse manure often used to make the compost. I don't know 
what all these pest killers are, probably mainly organic compounds, but 
their residues in quantity probably don't do much good. Spreading the stuff 
around the garden gives opportunity for the weather to disperse them, an 
action much more restricted in pots. I have heard Perlite has high fluoride 
content but I've not noticed any deleterious effects using it at up to 
three sevenths parts (about 42%) in a mix otherwise largely leafmold. The 
usual recommendation for Perlite is not more than 20 or 25% volume. Peat is 
acid and we have got used to handling that.

"Speaking of giving up I had a clump of Amaryllis belladonna that bloomed
for many years and then stopped for about three or four."

Amaryllis commonly grow in coastal areas, often not far above sea level. 
The water table must be close up to the bulbs and it must surely be 
The best display of Amaryllis belladonna that I have seen in the UK was on 
the southern coast of Cornwall - southerly aspect, slightly raised bed in 
front of the garden wall of a cottage, across the road was the beach, only 
a couple of feet above sea level. There were over 150 scapes spread along 
on the road and seaward side of the wall, a distance of about 20 yards. 
Yes, I counted them!! Breath-taking. Perhaps, Mary Sue, your bulbs are 
pining for some sea salt? Just a little, perhaps?

Regards Hamish

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