Sweet Pea Advice

I'm new to growing sweet peas and need some advice please. I have grown my sweet peas in root trainers and they are now falling over, they are about 10cm long. When do I plant them out and is it ok for them to fall over until planted out?

When they have several leaves, I nip out the stem below the growing point with my fingers. As Yorkie says, this makes them produce stronger and bushier plants which equals more flowers.  Mine tend to flop as they grow even after doing this but have been ok. If you keep the pots close to each other, their tendrils can tangle them together which may help them support each other, but they can be separated with care and nimble fingers before planting.

According to the RHS you should plant them out after the 'final spring frost', although I don't really know what that phrase means in practice. 

They are much tougher than they look, and if properly hardened off should be OK outdoors in a few weeks time unless we are having another really cold spell of weather at the time.

I used to sow them directly into the soil in early March with few problems, although I now sow them indoors about now (yesterday in fact  ) to make sure they get off to a good start.