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.