As autumn rolls in with shorter days and a noticeable chill in the air, the gardening calendar kicks into high gear. September may seem like a time to wind down, but it’s actually one of the busiest and most crucial months for garden care. From harvesting late summer crops to planting spring bulbs and preparing beds for the colder months ahead, there’s no shortage of tasks to tackle.
If there is one thing you should prioritise in your garden this September, however, experts from the Royal Horticultural Society (RHS) recommend dividing herbaceous perennials. This is the ideal time to divide most summer-flowering perennials as the weather is cooler the soil is still dry enough.
At this stage, plants are winding down their growth cycle, making the dividing process less stressful for them and allowing new divisions to settle in before winter.
Over time, many perennial plants become congested or begin to lose their vigour which means that clumps can become too large, with overcrowded roots competing for water and nutrients, leading to fewer flowers and less robust growth.
By carefully lifting and splitting these plants, gardeners can rejuvenate tired areas of their garden, encourage better blooming, and even create new plants without spending any money.
Some plants can be pulled apart by hand, while others with tough or fibrous roots may require tools such as garden forks, spades, or a knife to separate them into healthy sections.
The goal is to create new clumps that contain several strong shoots and plenty of healthy roots. After dividing, the new plants should be replanted as soon as possible, ideally in enriched soil that has been improved with compost or well-rotted organic matter.
They can be placed in the same spot or moved to another area of the garden, depending on your layout and the way you’d like your garden to look like, and water the newly planted divisions thoroughly.
Certain plants require a slightly different approach. For example, crocosmia and dierama form corm chains that are best handled carefully to avoid damage.
In fact, these plants may perform better when the corms are left connected, and they only need dividing every few years. Hostas, on the other hand, with their large, fibrous roots, can be sliced cleanly through with a spade and re-established with minimal fuss.
The RHS, however, has warned that if the autumn is too wet, it may be best to delay dividing certain perennials until spring. Excessively damp soil can make the process more difficult, increase the risk of root damage, and reduce the chances of creating new roots before the winter.