Herbaceous borders need more than just regular maintenance many clump forming perennials also require annual rejuvenation. Autumn into early winter is a perfect time to regenerate life into tired herbaceous perennials that combined make up your herbaceous border.
Fast growing perennials are likely to quickly outgrow there allowed space and compete with their companion plants. Dividing and restricting the growth of these fast growing herbaceous perennials will restore balance and give slower growing plants a chance to fight of the competition.
Lifting perennials in late Autumn or in early Spring depends upon the weather conditions, during a mild September to November, perennials like Monarda, Asters and Phlox can easily be lifted, split and replanted. Where as perennials that are not so hardy need to be left in the ground till the Spring, when they can be divided ready to burst into new growth.
Heavy clay soil may already be too wet in November! So leave the dividing of perennials until the Spring or alternatively improve the soil conditions by adding humus, well rotted organic matter or farm yard manure compost to help improve the soil structure. Likewise sandy soils can be improved with a regular helping of compost either when planting or as a mulch to help retain moisture.
Consider your planting scheme throughout the season, is there enough colour in Autumn and Spring? Perhaps you should plant a wider range of perennials like these Iris to extend the flowering season and even contemplate some winter interest with spring-flowering tulips or winter Hellebores.
Top Tip: When dividing herbaceous perennials select a few small well rooted stems or basal crowns to grow in 1 litre pots overwinter. Place these 1 Litre perennials in a cold glasshouse or cold frame, allowing their roots to develop during the winter months and come the spring you will have some reserve plants to either fill any gaps you have in your border, replace any that have died or exchange with your friends or family.