March is the month where so much in the garden needs doing. After the long winter suddenly there’s all this cutting back, pruning and dividing to do and it feels like there aren’t enough hours in the day.
Dividing is a horticultural term that simply means splitting a plant into smaller sections. Plants that are suitable for dividing are clump-forming perennials including ornamental grasses, and there are a number of reasons why you might need to do this. A plant might have got too big for its space and it needs reducing in size. The plant might have become woody in the centre and need rejuvenating so that it continues to keep flowering, or you might want to make some new plants for free to plant elsewhere in your garden.
The process is pretty straightforward. You’ll definitely need a spade and possibly two garden forks, and it’s useful to have a pair of secateurs and a pruning saw to hand too. It’s also a good idea to have a sheet or tarpaulin so that you don’t make a mess of your lawn or path.
- Dig around the plant using the spade and get underneath the root ball so that you can lift the plant out of the ground and on to the tarpaulin. Small plants with fibrous roots such as primulas or ajuga can generally be carefully teased apart. Larger plants with more congested roots need to be cut into sections. Often you can use the spade to slice the plant. Sometimes two garden forks inserted back-to-back into the root ball can be used to lever the plant apart. For plants with tough roots a sharp knife or a pruning saw may be needed.
- The centre of many perennials can become old and congested over time with fresher more vigorous growth around the edges and it’s this that you want to keep and replant, so discard any tough, woody bits.
- Replant the new sections, water in well and keep watered during dry spells.
- If you’re dividing in early spring and you have clay soil, use a wooden plank such as a scaffolding board placed on the soil and stand on this rather than the soil. This will stop the soil becoming compacted.
When to Divide
The best times to divide are mid-autumn or early spring – both have their pros and cons. Dividing in autumn means the plants have time to establish in warm, moist soil before winter sets in. However, if the autumn is particularly wet, which seems to be more commonplace due to climate change, newly divided plants can often struggle, their roots rotting in the waterlogged soil.
In early to mid-spring plants are coming back into growth so there’s lots of energy which helps them re-establish. They will, however, need to be kept watered through spring and into summer.
I tend to divide in March, mainly because many of my plants, especially the late-flowering perennials and grasses still look good in autumn and I can’t bring myself to cut them back so that they can be divided and moved, whereas in spring the garden feels like a blank canvas. The downside to this is that the last few springs have been really dry with none of the usual April showers which has meant some divided plants have struggled. The changing climate is certainly making gardening a good deal trickier!
Om Louise Curley
Louise is a horticulturalist, garden writer and author of the award-winning book The Cut Flower Patch. She’s passionate about the power of plants to make us feel happy and is an advocate for organic gardening and encouraging wildlife into gardens.Get to know Louise Curley
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