Now is a good time to do it. They may get beat up a bit over winter but they seem to come right back in spring. My first time planting them was around new years a year ago and they all took fine evetn planted in winter. Ive got around 8 or 10 of them planted out since then and every single one has had a delicate rootball. They never seem to be very rootbound. So take lots of care when removing them from the pot, the roots are not as robust as other fruit trees.