Posted: 02/05/2015 at 08:09
i think it's a bit early to divide a 2 year plant. Does it flower well? How much space of your available area does it take up? As it is your favourite plant in the garden I would leave it for a couple of years before dividing.
i divide anytime.....done it in autumn and spring. Even in winter. however, I think late summer....early September is prob best. I dig up the clumps....they are large things with a heavy deep root system. I use a sharp bread knife or saw to cut in half. Then I wash off with a hose to see clearly how the root system is and look where I can then pull apart. this requires a little strength, patience and logic.........you should feel/sense where the clump will separate. I pot up into good size pots using a mixture of mpc and a little dried manure or mushroom compost.