Planting small perennial plants outside in Scotland

bobsparkes

I have lots of small (3 to 4 inches) perennial plantlets (for example, Gaillardia, Echinacea and Polyanthus) raised from seed sown in the greenhouse in July. Would it be safe to plant them outside now, considering that in Scotland we often get frosts in September ? Would they survive the winter outside or should I keep them in the greenhouse until the Spring?

Fairygirl

I'd wait until next year 
They'll be sturdier, and bigger, and better able to cope. Polyanthus are pretty tough though, so  you could have a go with those. They certainly wouldn't need a greenhouse.
 
Gaillardias aren't reliably hardy here anyway, so you'd need to protect those. Echinaceas are hardy, but small plants would struggle. They both tend to be short lived too, so you may need to grow again in future.
I'd keep both of those in your greenhouse until they're growing really well next year. Small plants are very vulnerable to pests and diseases as well as weather. 

bobsparkes

Thank you, Fairygirl.
Unlike a lot of the advice from some suppliers (who work in the far south), thank you for appreciating that Scotland has a different climate. I will be able to pot on my perennial plantlets and keep them in an unheated polytunnel, where the temperature does dip below zero, but not severely so (because the chrysanths have survived therein for the past two years). I look forward to planting everything out in April.

Fairygirl

We obviously have differing conditions depending on where you are here too, but on average, we're about a month behind what happens in the far south, and autumn arrives in August. East tends to be a bit drier than the west. Southern Scotland is often a bit milder and warmer, but even so, it pays to wait with small plants. Large parts of this country have more in common with Scandinavia than with southern UK. Parts of it are Scandinavian 
We get the odd year that's more favourable [this year for example ] but it doesn't change the fact that ground takes longer to warm up and dry out. 

I learned the hard way, decades ago, that while you can plant stuff out in April in the south, you can't do it here