I don't think you would have a problem moving it now,from a planter into the garden..bearing in mind,they prefer Ericaceous Compost or acid soil.and some shade is more beneficial ,especially from early morning sun,in spring,as the new red foliage is easily burnt..just make sure you keep it very well watered,especially at this time of year..If you have Camellias,or Azaleas growing well,your soil should be suitable..

as long as the ground isn't frozen you can transplant a pot grown plant at any time of the year. make the hole at least half as big again as the pot so the roots have space to spread out and establish.