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Suppose the surface of earth is -349 Fahrenheit and survivors live deep underground dependent on geo-thermal energy.
They do farming in tunnels. They have enough energy (heat, electricity), fresh air (similar to the existing atmosphere, don't mind how for now) and water. What kind of vegetables and fruits could they grow with artificial sunlight?

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  • $\begingroup$ They probably couldn't grow anything thanks to lava streams. $\endgroup$ – KingraHoundoomJazz Feb 12 '17 at 19:49
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    $\begingroup$ At about 300 metres below the surface, the temperature wouldn't increase enough to make a difference. It increases by 25 degrees Centigrade per 1km, which is about 1 degree Fahrenheit per 70 ft. So unfortunately, if the surface is -400 Fahrenheit (-240 C), there won't be any survivors at 300 metres. They'd have to go to about 16 km for the temperature to reach 0. $\endgroup$ – Philip Rowlands Feb 12 '17 at 20:09
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    $\begingroup$ Can you flesh out the question a bit? Do they have access to our level of tech or do they have limitations of any kind? Do they have any insects for pollination or can they manually pollinate the plants with flowers? Largely put: plants doesn't care if the light is artificial or not, as long as one can provide the proper wavelengths. So what plants they can grow partially depends on the type of light available and if the plants are able to reproduce or not. $\endgroup$ – Mrkvička Feb 12 '17 at 20:11
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    $\begingroup$ They have higher technology than 2016. But not too futuristic. No insects at all. They should find another method. $\endgroup$ – UKS Feb 12 '17 at 20:14
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    $\begingroup$ /if the surface is -400 Fahrenheit (-240 C), there won't be any survivors at 300 metres./@Philip Rowlands. I wonder about that. I understood the subsurface at different depths to be at fairly constant temperature regardless of surface weather or temperature. Also you have these folks dependent on geothermal so they may have sited their digs on a hot spot. I would. $\endgroup$ – Willk Feb 12 '17 at 21:06
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Anything that can be grown hydroponically could be grown in the tunnels. So just about anything. Probably not mangoes.

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    $\begingroup$ I'm pretty sure that if they REALLY wanted to they could grow a mango as well. After all, soil isn't much more than minerals and dead organic stuff, and you have enough of both (you just need the necessary microfauna, but that should be fine $\endgroup$ – Hobbamok Apr 26 at 12:27
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Ignoring how deep they actually have to be (much much deeper than 300m) , they could grow anything.

Without insects, anything requiring pollination will have to be done manually, making it immensely labor intensive, but apart from that they're perfectly fine.

The first generation could only be hydroponic-able stuff, but after a while they have enough organic waste for regular soil, removing the last limit for what they can grow.

[Sidenote since you want to shoot your planet out of orbit: Stone is a bad insulator, but there are enough theories about life on extraorbital planets, copy from them what is theorized to be insulating enough]

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