How cold is too cold for Conifers?

[Blue Spruce]

I'm planning on starting some conifer seedlings, from seed. How cold is too cold for them the first year if I have them outside?

I could put them in a cold frame, but what if it gets to 20 below zero? Will I lose them if the roots freeze, etc.?

Thanks.

 

[Treeman14]

I think you should plan on some type of heating system to keep your trees from extended freezes. Occasional, short-term freezing of the soil will not do much damage, but if the freeze is prolonged, the frozen soil cannot provide moisture to the shoots and you end up with winter burn damage. I've heard of people using heating cables on raised planters to keep the roots from freezing. The soil should be kept moist but not wet. An anti-transpirant spray will reduce moisture loss. Mulch would also help minimize temperature fluctuations.

 

[Ray Morneau]

Hello, Blue Spruce --

Treeman14 has given you sound theory.

Still, consider your Montana environment. Ma Nature starts 'em without a cold frame, wires, and TLC. I would suggest that, if you're using local seed stock, then go "natural" -- the hardy ones will make it. (Plant more than you need to end up with on the theory that even if they all survive germination/initiation you may want to cull the runts of your litter.)

Not that you can't pamper them with heat -- BUT unless you have a conservatory to continue them in, you might be better off in the long run to get them used to livin' outdoors.