Sweet pea help please!

[Newton]

I sowed my free GYO seeds in root trainers last month and all germinated in about 5 days. I then put them in the GH. They are doing really well but maybe too well.

They are currently about 6 inches high! Should I be doing anything to slow them down. I heard that you could cut off the growing tips. But how much?

Will they survive the winter in the GH?

All advice welcomed. Never grown flowers before!

[Gearoid]

Pinch out the tops once you get the first three sets of leaves or so. That'll make them grow side shoots which should flower better.

They're hardy enough to get through the winter with minimal protection. A cool greenhouse would be fine.

[Two_Sheds]

If yours are growing really tall without showing any leaves, they're probably too dark and possibly too warm. Move them somewhere light and cool.

[Alison]

Move them somewhere light and cool.

I think the OP said they're in a cold greenhouse