Surely if you built a greenhouse on the surface, you could start it off by pumping in outside CO2 and using small tanks of O2 get the internal atmosphere started and then let the plants sustain the O2 (which if they made enough could be siphoned out and stored). You could generate heat from solar panels or a small reactor and let them grow in the martian soil...
But who wants asparagus? I might wait for the next planet that can grow cheeseburgers and potatoes...