Juniper hardiness after breaking dormancy

[keithl]

Do junipers lose any cold hardiness once they break their winter dormancy? I got to figure there is some reduction, but how much? Are they still good in a pot outside below 10F for example?

 

[MaciekA]

I don't think they lose hardiness in any significant way since they haven't spent the starch hoard yet and the starch/sugars in the wood are the physical, tangible manifestation of winter hardiness (sugar / starch = antifreeze). A millimeter of tip growth hasn't made a dent in that starch pile yet, and besides, even if it has, that tip is loaded with the stuff itself. Juniper foliage is quite plump and hardy and itself full of sugar in a way that, say, deciduous broadleaf leaves aren't. Junipers pause and resume growing in a much more gradual, much less step-wise way than , say, a cherry or maple (or even a pine) so they're adapted to take advantage of an odd warm winter spell much more than those species -- consider that it is commonly stated that the foliage itself in junipers (and perhaps other cupressaceae) is a significant storage location for fuel (sugars/starches, which as mentioned before are effectively antifreeze).

Now, whether your specific juniper will have trouble in upcoming cold weather snap or not is something one could only confidently answer by knowing the tree (and perhaps you as a grower, along with your growing setup) much better. You could be talking about a super strong nursery stock juniper, you could be talking about a barely-functioning mallsai cutting in potting soil. The latter might crumple under a cold snap even if what I say above is true, the former will punch far above its weight.

It's late-ish March so this time of year, if in doubt, trust your gut and bring things in overnight if/when a deep snap happens.

 

[roberthu]

Do junipers lose any cold hardiness once they break their winter dormancy? I got to figure there is some reduction, but how much? Are they still good in a pot outside below 10F for example?

Well I would never keep any potted trees outside with below 10F... I am lucky enough to be in a place where winter doesn't get below 25F often and I can get away with mulching for the most part. But I still pull trees in when the forecast shows 25F or lower.

 

[Wires_Guy_wires]

Junipers in mountainous areas get four seasons a day in spring and autumn, so I wouldn't worry a lot.