Thanks for the response - yeah I was worried it wouldn't survive outside in a pot (and I wasn't going to bury it). Good to know for the future. Would it have done any better if it had never been outside? I've seen another thread (on another site) where someone grew an apple tree from seed and kept it as a houseplant.

"Would it have done any better if it had never been outside? I've seen another thread (on another site) where someone grew an apple tree from seed and kept it as a houseplant."

No. Plants that grow naturally in temperate climates - like most of north America - seldom make successful houseplants. They need those seasonal temperature swings and light change to trigger their natural biological processes. You just cannot successfully replicate these conditions indoors - too warm, too dry and too dark, even with grow lights. An apple tree needs to go through dormancy and a period of cold to grow and thrive. To deny that by keeping the plant indoors as a houseplant will shorten its lifespan dramatically. Not to mention that it will be unlikely to ever flower - no vernalization - and won't produce fruit. What would be the point??

No it would not have been better if it had never been outside. It should have started outside and stayed there. Hardy plants from temperate or cold climates do not make successful houseplants.

the low growth seems to indicate the roots are not dead ... yet anyway ....

i needs to be hardened off to sunshine if it does eventually go outside ...

it should be planted in mother earth in early spring or early fall ... preferably it would have been while dormant ...

https://sites.google.com/site/tnarboretum/Home/planting-a-tree-or-shrub

trees prefer a drink ... and near drying.. before the next drink ... so if you keep it potted.. try to do that ...

seeds from known good apples ... does not necessarily come true ... meaning you may or may not get the exact apple you were eating ...

ken

Hopefully, I'm not to late to help save this baby and it still have some green buds/shoots and this long post is not for nothing!

This was posted in March and your pic is its green as if sprouting or starting to grow, when usually most trees that grow outside are dormant still, especially in Z6a.

I do not think that the fact it was grown inside is why this is happening. The mess up in time/temp indoors is bad, but unlikely to actually kill it so suddenly, it will be more of a gradual decline and then death, usually 1 season indoors is not good but will live with minimal growth the following season unless conditions are corrected.

My thoughts: Is it possible you brought it outside (march and outside in the pic), and you had a frost or large temp swing indoors/out which possibly killed/injured it which is why the top started to die? Even though apples are cold hardy, if it was never acclimated to the cold to go dormant in the fall and just brought out now, even a light frost can do some serious damage if there is green young leaves.

Also, I suspect it is also environmental since damage/death is going top/down at this specific time. Which means roots are possibly somewhat alive at this moment.

What I would do if you really want to try and save it:

If it's still alive and those sprouting buds are still alive I would make a clean cut right above the last living bud. And if the weather is at or below freezing (during the night as well), and you have an unheated garage or shed take it in their or if not possible try covering it with something. Cool is okay, but not freezing, And let it see the light whenever it gets above freezing. Or you could technically bring it back inside put near bright window until it warms up a bit since it's season/growth clock is already off. If your lucky, you will be left with a tiny stick since it was cut right above the last living shoots, but those living buds/shoots might grow a bit and maybe even sucker over the next couple months...but the goal is to preserve whatever is still alive.

If it does survive the next couple months it's a great sign.