It is very expensive to keep buying plants to fill every space but ground cover does keep the weeding down and improve. Happily in the autumn and spring there are plenty of plants, including ground cover plants, that can be divided and anything which helps garden economy is definitely worth the trouble.
Anemone japonica, primulas, hellebores, Alchemilla mollis (Lady’s Mantle), Tolmiea menziesii (pig-a-back), bergenia (elephant ears),, , bearded , Michaelmas daisies, phlox, heleniums, lupins, delphiniums, chives, Stachys lanata and even shrubs like heather, Kerria japonica and Scotch rose all divide splendidly.
The majority of these plants should be divided between October and April, except bearded iris which should be divided after flowering in July, and hellebores in early September or in early spring (I have divided them in the summer with good results but they were watered well for three weeks before dividing), andshould be divided when they have just flowered and are still ‘green’ (in leaf).
The method of dividing varies, depending on the type of root system – fibrous, tuber, rhizome or those with a woody crown.
The easiest plants to divide are those with fibrous roots such as primulas, and small like Tolmiea menziesii and Alchemilla mollis. In a low maintenance garden Tolmica menziesii, pleasing yellow/green leafed ground cover, is well worth dividing to be used elsewhere and save the weeding. Alchemilla mollis dies back in the winter but it is decorative ground cover also worth dividing although it will seed itself.
First dig up the fibrous rooted plants and gently tease away a section by hand and then replant in a vacant space allowing room for growth, for both these plants spread fairly vigorously.
Larger clumps of Michaelmas daisies or delphiniums need two garden forks, placed back to back down the centre of the plant’s roots and then prised apart. A sharp knife is best for the fleshy root system of say the peony, which should be divided in October.
Rhizomes like bergenia and bearded iris which have long, thick, horizontal roots like old gnarled tree roots should be cut off in 2-3in (5-7.5 cm) sections each with the new growth of young leaves on them. These sections should then be planted horizontally just below the soil or on the soil, at whichever depth they were growing.
Tubers, such asand , only need to be cut into pieces; providing each piece has a bud or an eye on it, it can then be put back into the soil and should grow.
Anemone japonica needs careful dividing andin spring.