Most herbaceous perennials such as bedding plants and perennial ornamental grasses are long-lasting and easy to look after and can be easily propagated by splitting. After a few years in the same place, herbaceous perennials often form dense plants with an equally dense root system. If you want to propagate herbaceous perennials, you need to split the plants lengthwise along with their roots using your hands, a knife or a spade.
Once the plants are split, they can be replanted in the desired spot in the garden and given a good watering. This rejuvenating procedure will ensure new growth and you can look forward to twice as many flowers. The best time for splitting and rejuvenating herbaceous perennials is in autumn after they have been pruned or in early spring. Early flowering herbaceous perennials should be split in August or straight after they have flowered.