Im batteling with Echinacea at the moment but verbena but, get them in the fridge for 2-3 weeks to make them think they have had the big chill...sow it and leave it. It can take aagggeeeesssssss to germinate so be patient. Scabiosa, I did in a seed tray in a cold green house and they are all up. Took about 10 days. Im not sure about the rest, sorry
I have had success in the past with echinacea, verbena and scabious - sowed them on the surface of seed compost, covered with thin layer compost, put lid on propagator and given some bottom heat - all have come up in a couple of weeks. Take the lid off when they have germinated to stop them getting too damp (makes it easier for them to go mouldy).
Verbena also comes up all over my garden from plants that went to seed the previous year - so I'm sure that would be alright without bottom heat.
I'd just put them all on some seed compost with grit on top. Water and leave in the cold greenhouse. It won't be cold in there much longer.
I'd have probaly sown some when I harvested them. Half then and half now, bound to have success one way or the other. Rarely use any heat though I've got a few in an electric propagator now and a control sowing in the cold GH. If I get round to it I'll keep records of what did best. Some seeds really don't like to be too warm and some respond well to the alternate hot and cold of an unheated greenhouse
http://theseedsite.co.uk/ There's a lot of information here about how to germinate specific seeds
^^^My seed guru
Just sow them Red Dahlia, nothing to lose. Seeds grew before propagators were invented.
Red - I only remember ever having chilled aquilegia seeds, so definitely didn't chill first. But Nut is right, I'm sure a greenhouse will be plenty warm enough for them now (I planted mine in Feb). I would try the bottle propagator - they like damp as well as warm until they pop up.
One warning, I have never got echinaceas big enough to flower in their first year - but they make good enough plants to over winter well. I have 10 "pink parasols" sitting in my greenhouse ready to wow me with their flowers this summer (or else!) Sometimes it feels like you need a lot of patience for this seed sowing lark !!
I can germinate an echinacea but I absolutely can't keep the b......s alive for more than a season.