Spring frost damage threshold

[Xenie]

If a cold hardy conifer pushes new growth early in the spring, and this growth event is followed by a cold spell, how cold does it have to get to damage the tender new foliage? Are near freezing temperaters okay? I would imagine weather in the teens could be harmful, but what about weather at or around 32?

 

[coh]

My experience has been that most hardy trees I've grown can stand temps down to about 29 F (and maybe 28 F) for a few hours without much damage once they've started to leaf out. This is based mostly
on landscape plants as I'll usually move any bonsai into shelters if temps are expected to go below freezing once they've leafed out.