Verbena Bonariensis - tiny seedlings?

in Plants
I have a tray of verbena B seedlings that have remained tiny since they appeared about three weeks ago. They have been in a heated propagator in my greenhouse. They often seed freely in the garden so why are these struggling? Should I take them out of the propagator?




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They need nice light soil.
They certainly shouldn't still be on any heat once they germinate.
MPC is fine at this time of year for seed. Bit of additional grit or Perlite really helps to keep it lighter. It's only when autumn sowing that seed compost is really needed, because you don't want lots of nutrients for small plants over winter.
I tried a peat free compost this year and did a trial when I sowed my sweet peas. I used a compost I normally use, with some Perlite, and used the peat free one [Miracle Gro] as it was. There didn't seem to be too much of a difference. Maybe I was lucky.
I think it could be better to use sieved garden soil with grit, rather than some of these composts. There's been a lot of threads recently about how poor many of them are.
It looked exactly like the dust found in my vacuum bag.
Seed compost above looks dire.
I didn't use the stuff I had for my tomatoes or basil, but I used most of it in a border I was redoing with some new, or moved, plants etc. It's very fibrous, but the plants are all fine.
I'd be quite wary of using some of these composts for anything very small or anything that needed a light medium to grow in.
As a general rule, once seeds have germinated in a heated propagator, can they be taken straight out and left on the greenhouse bench?
My Vitapod has extendable walls to make them higher, for taller plants, I guess they shouldn't be needed.
I think you could probably do them in the greenhouse, without any heat, from just now
It's why the main plants don't always survive winter either