On 12 Mar 2012 20:26:29 GMT, "AL_n" wrote:

Can anyone tell me some reasons why seedlings sometimes flop over and die,
while others (of the same variety) don't?

Al

Some will die as a fact of life but if you have a major spate of this
then one likely cause is what's known as "damping off disease". This
fungal disease usually strikes and kills an entire tray-full quite
quickly but sometimes if you have, say, a mix of closely sown
seedlings and some more spaced out then the disease may hit the close
ones but not affect the more spaced out ones.

The treatment for this problem used to be something called Cheshunt
Compound but, just like everything that's useful in pest/disease
control, the rules changed and it's no longer on the market. The only
currently available substitute is Bayer Fruit and Vegetable Disease
Control though there are many who are skeptical about its
effectiveness.

Prevention being better than cure, ways to hopefully prevent the
problem are (1) always use clean seed trays and fresh seed compost
rather than multipurpose, (2) make sure there's good ventilation -
stagnant moist air is a real problem for seedlings - remove them from
the propagator once they've germinated, (3) water only with tap water
that's been allowed to stand for a couple of days to let the chlorine
evaporate, don't use rainwater and (4) don't over-water.

I moisten the compost before sowing and then leave things in the
propagator until seeds germinate - sealed in, the compost usually
stays moist enough. Once the seeds have germinated I remove the tray
from the propagator and, until the seedlings are big enough to
transplant, I use a mister to keep them just moist. I don't use a
watering can until they've been pricked out and are growing in their
own space.

Cheers, Jake
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Urgling happily from the dryer end of Swansea Bay.