Can trees be propagated/started over winter indoors, or would that 'tire them out'?

Question

I found a calendar of propagation activities which seems very helpful, and it says that hardwood cuttings can be taken and started for deciduous trees throughout winter. I imagine those cuttings would freeze and be destroyed if left on their own poked into some soil (if the soil is even unfrozen enough to receive them). That makes me think those hardwood cuttings should be grown in a somewhat protected space, either kept in cool dark conditions (in a garage or maybe outdoors with a thick topping of mulch) or nursed to life under a light, with a heat mat, etc.

Any clarification about the above would be appreciated, but my main question is this: can propagated trees that would normally be dormant over winter be started out indoors? If not, why/what bad outcome would they eventually reach?

Example: a bunch of seeds or hardwood cuttings of deciduous trees are planted in air-pruning pots or beds and grown indoors over winter. Around/after last frost in the spring, they're either planted into a larger pot/raised bed to be transplanted or heeled in after 1 year; or planted into permanent beds to grow for 2-3 years before transplanting; or planted into their permanent location to live out their life. For every winter after the one they're started in, they'll be outdoors in the ground exposed to zone 4/5 conditions.

Will baby trees grown this way be crippled by having grown in nursed conditions the winter they're started and then all through summer, basically experiencing a much longer growing season than they ever will in the future?

Answer 1

Advice like that calendar is useless if you don't know what climate it refers to, and I couldn't find any information about that on the rest of the site.

Autumn is a good time to take hardwood cuttings, but if you are growing them outdoors they need to have rooted before the ground gets too cold. In the UK that would mean taking the cuttings in September when the parent plant is at the end of its growing season, not in mid winter. Trying to plant cuttings in frozen ground is pointless IMO.

Some tree seeds need a spell of freezing temperatures before they will germinate. If you want to germinate them indoors you may need to keep them in your fridge for a while, but the details depend very much on the species.

To answer your general point, baby trees aren't like baby humans, they have evolved to propagate themselves without any help. If the trees are frost hardy, it doesn't matter at all if a six-inch tall seedling gets buried in a foot of snow for a few weeks! You are more likely to get problems by trying to grow them indoors, for example with too much heat, not enough light, and poor air circulation.

Growing them outdoors in pots can be worse than in the ground, because the pot is more exposed to the air temperature and can get colder than earth a few inches below the surface.