if your soil does n't suit , plant in containers in ericaceous compost .
if yours is acid , free-draining and nutritious , they 'll thrive , but they mope in alkaline or neutral ground .
so , if you do n't want to buy new , take root cuttings and bring them on as replacements .
the best time to take cuttings is between september and february , but you can see them in flower , select your favourites and enjoy this year 's display .