I don't know because when I've looked at punnets of seedlings it says to protect from frost. I normally grow them from seed, but usually in the warmer months. 2 years ago I got lazy and didn't pull them out straight away when they died, so unpicked pods dropped their peas on the ground. I didn't realise this until around the middle of June when all these seedlings started coming up. I left them there to see what would happen and after several -8C nights, they were still there doing their stuff. They weren't that big when I wanted to prepare the garden for the next summers planting, so I can't say if they would've produced pods or whether frost might affect the flowers because they didn't get that far.
Only one way to find out! Pop some in and see what happens. I've seen them at the nursery as seedings in the last 2 weeks, so they must be able to tolerate some cold.
Jane