Greenhouse, no action.

I have failed to get even one seed germinating from two sowings of tagetes. Can only assume the whole packet was no good.

 

Not very. It is an assembly of dry ingredients ,only some of which may have been 'composted'.Random weedseeds germinate. The peat based would provide sedges which suggest not sterile either.
I think the problem is likely to be overwatering/lack of drainage* as well as poor seed quality.
My own experiences this year with Westlands Gro-sure (sold as 'peat reduced' !) have resulted in good germination as usual of realseeds , my main supplier and poor to dismal in the case of Mr F flower seeds. Own saved flower seeds ;ie fresh from 24 ,have done well side by side, my suspicion is 'old' new packeted seeds.
*I notice that plants are coming in pots with large(r) drainage holes, up to 16mm, and peatfree compost. Perhaps seed trays need this as well ? It is desirable to have slatted surfaces and no polythene underneath to ensure excess water may escape.

 

Non heated Greenhouse, well situated, been producing seedling for 20 years - inc Cucumbers. I have germinated 2 out of 10 seeds I bought, normally it is ten. Pipernex FI great variety.
I have other flowers I have not listed because I can't spell their names. About 30 species in all. All at two seed stage. I have used two brands of peat free compost.

 

I find the peat free compost is bagged up quickly and it's far better to let it compost for a few months before using it.
I also don't particularly like the stuff and just sow in my own home made compost where I get far better results. The problem I have is getting the watering right with peat free and I've had seeds just rot off with a normal soaking method that you would have used in the past. The best results now is to keep the soil far dryer than I would have previously and only water more when the seed has germinated.

 

I know peat compost never been sterilised ,but the origin of peat is very different from the origin of peat free and may well contain composted diseased plant materials.

I agree over wet seedlings are more likely to damp off.

 

At the risk of bringing down the wrath of someone or other, may I name the brand of compost that I used, for the first time, this year?
Jack’s Magic.

 

When I had to give up driving in 2015 due to my Eyesight I don't visit any garden centres for any bagged compost.
I use my own sifted compost mixed with equal parts of Coir, feed and Perlite,
the only problem I have is poor seed contents and of course the UK weather.