How to Divide and Replant Perennials in Late Summer
Key Takeaways
- Late summer to early autumn is the ideal time to divide most perennial plants in UK gardens - the soil is warm and roots establish before winter
- Dividing perennials every 3-4 years keeps plants vigorous, boosts flowering, and prevents bare centres from forming in clumps
- Use a quality pair of secateurs to cut back foliage before lifting, making the division process cleaner and easier to manage
- A stainless steel border trowel and hand fork are the two most useful tools for teasing root clumps apart without damaging them
- Water newly divided plants well and keep the soil moist for at least 2-3 weeks while they settle into their new positions
Suggested reading: Check our essential hand tools guide and summer watering guide for more tips.
Why You Should Divide Your Perennials
If you have clumps of perennials that have been in the same spot for three years or more, there is a good chance they are ready for dividing. Over time, most clump-forming perennials develop congested root systems. The centre of the clump starts to die back, flowering slows down, and the plant spreads itself thin trying to compete with its own roots.
Dividing solves all of this in one go. You lift the clump, split it into several smaller sections, and replant them with fresh soil and room to grow. Each division becomes a brand new plant that will flower more freely than the congested original. It is the cheapest way to multiply your plants and keep your borders looking their best.
Which Perennials to Divide in Late Summer
Not every perennial should be divided now. Late summer to early autumn (late July through September) is the window for perennials that flower in spring or early summer. These plants have finished their bloom cycle and are entering a period of root growth rather than top growth, which means they recover from division much faster.
Good candidates for late-summer division include:
- Bearded irises - divide every 3-4 years after flowering, discard old central rhizomes
- Daylilies (Hemerocallis) - large clumps respond well to division and bloom better the following year
- Hostas - divide before the leaves fully die back so you can see the crown structure
- Lupins - split after the main flowering period, though they prefer being left alone if happy
- Primulas - divide after flowering while the soil is still warm
- Hardy geraniums (cranesbills) - these spread fast and respond brilliantly to being split every few years
- Acanthus - divide carefully as they have thick, brittle roots
Perennials that flower in late summer or autumn (like asters, sedums, and rudbeckias) are better left until spring. Dividing them now while they are preparing to flower would set them back significantly. If you are unsure, check the plant's usual flowering period: if it has already flowered this year, it is safe to divide.
Tools You Will Need
You do not need a shed full of specialist gear to divide perennials, but having the right tools makes the job faster and reduces damage to the plants. Here are the essentials:
Felco 2 Secateurs - You will use these constantly during division work. Cutting back foliage before lifting a clump makes the whole process cleaner and gives you a better view of the root structure. The Felco 2 is the UK gardener's standard for good reason: Swiss-made blades, replaceable parts, and a comfortable grip that lasts through a full afternoon of dividing.
Burgon & Ball RHS Stainless Hand Trowel - This trowel is perfect for lifting small to medium clumps and for digging replanting holes. The stainless steel head resists rust, and the ergonomic handle gives you good handling without being bulky. It is the tool you will reach for most often.
Kent & Stowe Stainless Steel Hand Fork - The hand fork is your best friend when teasing root clumps apart. Push it into the crown of the clump and gently lever sections away. The stainless steel tines are strong enough to work through compacted roots without bending.
Kent & Stowe Stainless Steel Perennial Spade - For large, established clumps (think mature hostas or established daylilies), a border spade is much more effective than a trowel. The pointed head slices through dense root balls cleanly, and the smaller blade size means you can work between other plants without damaging them.
Briers Multi-Task Gardening Gloves - Dividing perennials is a hands-in-the-soil job. A decent pair of gardening gloves protects your hands from scratches and soil without losing the dexterity you need for delicate root work. These Briers gloves strike that balance well.
You will also need a bag of multipurpose compost or well-rotted organic matter to mix into the replanting holes, a watering can or hose with a gentle spray nozzle, and some garden twine or plant labels if you are keeping track of different varieties.
How to Divide Perennials - Step by Step
Step 1: Water the plant a day before
A well-watered clump is much easier to divide than a dry one. Give the plant a thorough soaking 12-24 hours before you plan to lift it. The roots will be more flexible and the soil will hold together better around the root ball.
Step 2: Cut back the foliage
Use your secateurs to trim the top growth back to about 10-15cm from the ground. This reduces water loss while the plant is recovering and makes the clump lighter and easier to handle. For hostas and daylilies, cut the leaves back to a fan shape about 10cm above the crown.
Step 3: Lift the clump
Insert your border spade or hand trowel several centimetres away from the base of the clump to avoid cutting through the main root mass. Work your way around the plant, gently levering upwards as you go. For large clumps, you may need to cut through some outer roots to free it. Do not worry about this - perennials are tougher than they look, and any roots you cut will regrow.
Step 4: Divide the clump
Once the clump is lifted, shake off as much loose soil as possible so you can see the root structure. For loose-rooted perennials like hardy geraniums, you can often pull sections apart by hand. For denser clumps like hostas or daylilies, use two hand forks back-to-back in the centre of the crown and gently prise them apart.
For very tough clumps, use your perennial spade or a sharp knife to cut through the crown, making sure each division has at least two or three healthy shoots and a decent root system.
Step 5: Replant immediately
Dig a hole large enough to accommodate the roots without cramping them. Mix in some multipurpose compost or well-rotted organic matter. Place the division at the same depth it was growing before - planting too deep is one of the most common mistakes. Firm the soil around the roots gently with your hands, then water thoroughly.
Step 6: Water and mulch
Newly divided plants need consistent moisture while they establish. Water them deeply twice a week for the first month unless the weather is very wet. A layer of organic mulch around the base (but not touching the crown) helps retain moisture and keeps the soil temperature stable as we move into autumn.
Common Mistakes to Avoid
- Dividing at the wrong time - Splitting late-flowering perennials in summer will cost you this year's blooms. Stick to plants that have already flowered.
- Making divisions too small - Each division needs at least 2-3 healthy shoots and a decent root section. Tiny divisions take years to establish and rarely flower well in their first season.
- Letting roots dry out - Once lifted, keep the roots covered with a damp cloth or get them into the ground within a few hours. Exposed roots dry out fast in summer heat.
- Planting too deep - The crown (where shoots meet roots) should sit at soil level. Burying it invites rot, especially through autumn and winter.
- Skipping the aftercare - Watering for the first few weeks is not optional. New divisions have a reduced root system and cannot support themselves without help.
Frequently Asked Questions
Final Verdict
Dividing perennials is one of those gardening jobs that feels intimidating until you try it once. After that, you will wonder why you waited so long. The benefits are immediate: healthier plants, more flowers, and free plants for filling gaps in your borders or sharing with friends.
The key is timing and preparation. Stick to perennials that have finished flowering, water them well beforehand, and have your tools ready. A good hand trowel and a hand fork will cover most jobs. For larger clumps, a perennial spade makes the work much easier on your back and your plants.
Late summer is the ideal window for this job in UK gardens. The soil is still warm from summer sun, autumn rain is usually on the way, and your perennials have months of gentle weather ahead to settle in before winter. Get them divided now, and next spring you will see the difference in every border.
Read our full guide to essential garden hand tools for more on choosing the right equipment for jobs like this.
Alex Green writes about vegetable growing, plant care and small-space gardening for MyLushGarden.
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Last reviewed: July 28, 2026 ยท Evidence-based content ยท Contains affiliate links