Posted: 04/07/2016 at 19:18
I've been doing this for a while now but mostly to rescue roses not doing too well in crowded borders.
Make sure their root ball is well watered about an hour before you want to move it and then, as ladybird says, dig up as much as you can. I then re-plant in decent sized pots - just large plastic ones about 50 to 60cms wide and deep and fill with good quality John Innes 3 type compost and water well. Then I remove broken, sickly or spindly branches and take off all buds and flowers.
Keep in a shady spot for a week or two while they get over the shock and then they can cope with partial sun as long as you water regularly. I'm leaving mine in their pots at least a whole season so they redevelop a strong root system before being planted out in a well prepared bed.