Would it be possible to have a building that could change the temperature of the world or maybe change the months that plants can be grown. Some drawbacks could be massive power draw and research requirements. A chance of failure which could result in the world being even more inhospitable, and during the process some very dangerous weather (More frequent events)
Given Mars planet terraformation (only put some atmosphere) is supposed to take at least several decades (in the best projections) with the efforts of a full planet population, I doubt 15 colonists could undertake this job. ::)
But it could be a fun global objective! ;D
might be a better idea to build an enclosed greenhouse to grow the plants (in cold climates you add heaters to get the room temp over 10c)
It's worth noting you can even do this ^ in mountains if you use fertilizer pumps.
It's a bit less fiddly than hydroponics and your plants won't all die every time there's a solar flare.. Unless the room gets too cold.