On 05/06/20 14:04, Nick Maclaren wrote:
In article ,
Jeff Layman wrote:

My problem is with seed compost, because I can't think of how to
sterilise the soil without acquiring another large device - and I have
no space left for storage.

Have you got a problem with soil-borne pathogens? I just wonder because
I not only do not sterilise any seed compost I use, but I no longer wash
the used pots I sow seeds in. I have had problems in the past with
damping-off in seed-trays covered with a plastic propagator lid, but not
recently, and I can't remember any recent problems with seeds sown in
small pots.

Oh, I gave up washing pots some time ago. It's not for that reason,
but to reduce the weed seed load for seeds that are difficult or slow
to germinate or difficult to identify as seedlings.

I do have a problem with soil-borne pathogens, but they don't seem to
be as active in pots, and I don't know what they are. Except for
white rot, eelworms and spraing, which I have identified but do not
affect seeds.

Although it may not be perfect for sterilising, have you tried spraying
hydrogen peroxide solution on the compost an hour or so before sowing?
It shouldn't affect the seeds (except that it /might/ improve
germination of some recalcitrant seeds), and doesn't leave any residue.

No, but it won't help - I do use household bleach on seeds (including
ones that have already sprouted) to kill surface mould, and it doesn't
seem to affect plants significantly. Chemicals won't do the job; only
steam would.

I misunderstood the reason for the sterilisation! How about a different
tack if you have the space and time...

Prepare the compost as you would for sowing, but don't sow anything.
Water well, and cover with something transparent/translucent. Leave to
allow weeds to germinate. When they have, hoe or remove them. Turn the
compost over, water again, cover, and leave for the slower-germinating
or deeper weed seeds to appear. Hoe or remove as before. If you think
there could be more, you could repeat again but I doubt it would be
necessary. Then sow the seeds you want. I admit it's a bit of a
rigmarole, but it's free!

--

Jeff