Growing in coir

Tom Mitchell
Tue, 30 Dec 2008 02:14:40 PST
As a novice to growing bulbs (a neo-geophyteophile?) I hesitate to  
offer anything resembling 'advice'. However, I am propagating plants  
of all kinds, including many bulbs, on a large scale at the moment  
and I am conducting an informal experiment comparing coir and peat as  
growing media. This isn't a scientific experiment with proper  
controls, merely an attempt to establish anecdotally whether coir is  
better, worse or about the same as peat as a medium in which to raise  
healthy plants in plastic pots.

The tentative conclusion is that coir is at least as good and in some  
cases better than peat. It slumps less in the pot over time, it holds  
water better, without remaining sodden (something to do with air- 
filled porosity, I'm told) and it is easy to re-wet. Most  
importantly, the plants are healthy and in some cases appear to have  
better root growth than in peat. The main potential disadvantage is  
that micronutrients, especially iron and manganese, become locked up  
over time unless your water supply has a pH lower than about 6.5. My  
water supply is alkaline so I acidify it with nitric acid (citric  
acid also works).

Here in the UK peat is a big environmental issue and so there is a  
marketing advantage to nurseries that use alternatives. I've sourced  
my coir very carefully from a reliable importer. The quality varies  
enormously and I'm guessing that the problems that Thomas experienced  
were related to the batch not the coir itself. Horticultural coir,  
when properly made, is inert, has a very low nutrient content (except  
a bit of K) and definitely doesn't promote fungal growth.

Incidentally, these days I sow almost all my seeds (except some slow  
germinators) in pure coir, with great success. I have had negligible  
problems with damping-off in this medium and find that seedlings are  
easy to prick out of such a light compost.

These are early days for my 'experiment' and I'd love to hear the  
thoughts of more experienced growers.

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