Dividing plants is one of the easiest ways to keep them healthy while getting extra plants for free. But timing matters.
Some perennials respond best when they’re divided shortly after flowering, giving them plenty of time to produce new roots before autumn arrives. Leave them too long, and they can become overcrowded, flower less freely and be harder to separate.
Here are five plants that are well worth dividing as soon as they’ve finished flowering.
1. Bearded Iris
Bearded irises are probably the best-known plants for post-flowering division.
As the thick rhizomes spread, the centre of the clump often becomes crowded and stops flowering well. Lifting and dividing the healthiest outer rhizomes every three to five years keeps plants vigorous and encourages a much better display.
Replant each rhizome with its top exposed to the sun, as planting too deeply can lead to poor flowering and rot.
2. Hardy Geranium
Hardy geraniums quickly form generous clumps that can outgrow their space.
Once the main flush of flowers has finished, lift the plant and split it into smaller sections using a spade or two garden forks back to back.
Replant the divisions immediately, water them well and they’ll soon establish, often producing fresh foliage and occasionally another flush of flowers before autumn.
3. Primroses
Primroses naturally multiply over time, forming dense clumps.
Once flowering has finished, gently lift the plant and tease the crowns apart by hand. Each healthy section can then be replanted elsewhere in the garden or shared with friends.
Dividing every few years helps maintain strong flowering and prevents overcrowding.
4. Aubrieta
Aubrieta often becomes woody in the centre as it ages.
While many gardeners simply trim it after flowering, older plants can also be divided if they’ve formed sizeable clumps. Replant healthy outer sections into free-draining soil where they’ll quickly establish.
It’s an excellent way to create more plants for rockeries, walls and gravel gardens without buying new ones.
5. Pulmonaria
Pulmonaria, also known as lungwort, benefits from occasional division once its spring flowers have faded.
By midsummer, the attractive spotted foliage often becomes the main feature, and dividing the plant helps maintain healthy growth while preventing congested clumps.
Replant divisions into moist, humus-rich soil in partial shade, keeping them well watered until established.
How to Divide Perennials Successfully
Most perennial divisions follow the same basic process:
- Water the plant well the day before lifting it.
- Use a garden fork or spade to lift the entire clump.
- Remove any dead or damaged growth.
- Split the plant into healthy sections with good roots attached.
- Replant the divisions straight away.
- Water thoroughly and keep the soil moist while they establish.
Avoid leaving lifted plants sitting in the sun for long periods, as the roots can dry out surprisingly quickly.
Why Dividing Plants Is Worth the Effort
Regular division offers several benefits:
- Encourages stronger flowering.
- Prevents overcrowded clumps.
- Keeps plants healthy and vigorous.
- Creates free plants for other parts of the garden.
- Helps rejuvenate older perennials.
A couple of hours spent dividing plants can transform next year’s borders without costing a penny.
Final Thoughts
Many of the UK’s favourite perennials perform better when they’re divided every few years, and the weeks immediately after flowering are often the perfect opportunity.
Whether it’s bearded irises, hardy geraniums or primroses, dividing plants now gives them time to settle before autumn and rewards you with healthier growth and more flowers in the seasons ahead. Best of all, you’ll have plenty of extra plants to fill gaps in your borders or share with fellow gardeners.
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