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Despite being advised to heel in trees or simply cover potted trees in mulch over winter, I did bring some potted trees indoors in a dark, cool (~50F), fairly dry (~30% relative humidity) basement. Sure enough they are leafing out before their outdoor counterparts and while nighttime temps still dip into <30F freezing temps.

What's the best path forward for these trees to survive and eventually acclimate to a planted place? I've had young trees seem to die off in the past only to burst back into life at some seemingly random point over summer, so maybe it's worth prioritizing their acclimation to the outdoor climate even if they lose a batch of leaves/buds from it.

The species in question are hazelnut, linden, black locust, and apple.

Some options I've considered:

Leave them in the garage til it's warmer, and if so, what kind of minimum temps are OK for them (does it need to be >32F or can they handle some frost)? If in the garage, should I water them or put them in a slightly brighter area? If bringing them outside, any precautions I should take, like covering the pots in mulch as I would've in autumn?

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Since you don't say what species they are, we can't guess whether they are frost hardy or not.

If you keep them in the dark from now on, as soon as the energy resources stored in the leaf buds are exhausted the new leaves will start to die, since they can't do photosynthesis without light.

I would guess (and it is a guess, given the lack of information) the most critical thing is to get them into full outdoor light conditions. Even bright natural light indoors is a factor of 10 times weaker.

If that means they lose their developing leaves to frost damage, well, there's always a chance they will regrow when the conditions are right. After all, trees have evolved to survive decades or even centuries of occasional "unseasonal" weather conditions during their life span.

The basic mistake here was keeping them at 50F. As a rule of thumb, night time temperatures of 40F or 5C are when plant growth stops and plants become dormant for winter. Once they are dormant, most deciduous trees can survive any amount of frost, even when they are seedlings less than one year old, especially since the roots are protected from frost by being in the ground. That's why heeling in trees that can't be planted immediately is a good strategy, so long as the trees are dormant before you move them.

  • Woops, sorry - hazelnut, linden, black locust, and apple are the species in the garage. My intuition agrees with your answer: these leaves are destined to die in darkness and dryness indoors, so I may as well put them in a shadier spot outdoors and have them start acclimating, however harmful that may be. Maybe I should also mulch around the pots, to protect their roots from freezing in case temperatures are that bad. – cr0 Apr 4 at 0:43

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