Protection of new Japanese Red Pine seedling in winter

Hi!

In mid-November, I put several Japanese Red pine seeds in a tray on a rack, outside the house, in a relatively sheltered area.

Today (11 February), I noticed that a few have already started germinating and have their heads poking out of the soil.

I was wondering, giving that's still Winter in the UK, what would you recommend me to do to make sure they won't die until spring? Do you think I can safely let me them outside like this?

Thank you

 

Definitely want to keep them frost-free, an unheated greenhouse or similar should be OK.

 

Thank you @Michael F. I will protect them. I've noticed that for now only some the Japanese Red Pine seeds have come up. None of my Black pine and White pine ones have come up yet. I'll protect those too when they do.