HOW TO DIVIDE PERENNIALS: A STEP-BY-STEP GUIDE FOR HEALTHY PLANTS
How & when to divide perennial plants for stronger growth and more blooms
Dividing hostas. Photo by: VH-studio/ Shutterstock.
Dividing perennials is an essential gardening task that keeps plants healthy, encourages better blooms, and helps you expand your garden. Knowing when to divide perennials is key, and that depends on their blooming season—spring-blooming perennials are best divided in fall, while fall-blooming perennials should be divided in spring.
Dividing perennials not only helps prevent overcrowding but also reinvigorates plants, ensuring they thrive year after year. If you've noticed your perennials struggling, dividing them at the right time can make all the difference.
On this page:- How to Tell When a Perennial Needs Dividing
- When to Divide Perennials
- How to Divide Perennials: Step-by-Step Guide
- Tips for Success When Dividing Perennials
- Common Mistakes to Avoid When Dividing Perennials
SIGNS THAT A PERENNIAL NEEDS DIVIDING
If you notice any of these issues, it’s time to divide plants to give them a fresh start:
- Reduced blooming: If your plant is producing fewer or smaller flowers year after year
- Overcrowding: Dense clumps become too large
- Thinning center: A dead or bare center in a clump-forming perennial
- Poor vigor: If your plant looks weak or unhealthy despite proper care
- Root congestion: If you lift a perennial and notice tightly packed roots or circling root growth
Regularly checking for these signs, especially in plants that have been in place for several seasons, can help you determine the best time to divide. Some fast-growing perennials may need division as often as every two to three years, while others can go five years or more before requiring attention.
Keep in mind that not all perennials need to be divided regularly (see below for the exceptions).
Photo by: Milovzarova Elena / Shutterstock.
WHEN TO DIVIDE PERENNIALS
The best time to divide a perennial depends on its bloom cycle. A general rule is:
Dividing in Fall: Best for Spring-Blooming Perennials
Perennials that bloom in spring should be divided in early fall, ideally about 4 to 6 weeks before the first frost, this allows them time to establish roots before their next growing season. The cooler temperatures and increased rainfall help plants reestablish before winter dormancy. Examples of spring-blooming perennials to divide in fall:
- Iris
- Daylilies
- Hostas
- Phlox
- Salvia
- Asiatic lily
- Astilbe
- Coneflower
- Heuchera
- Coreopsis
- Shasta daisy
- Rudbeckia
Dividing in Spring: Best for Fall-Blooming Perennials
For perennials that bloom in late summer or fall, spring division prevents interruption of their bloom cycle and gives them the entire growing season to develop a strong root system before summer. The best time is early spring, just as new growth emerges. Examples of fall-blooming perennials to divide in spring:
- Aster
- Goldenrod
- Sedum
- Chrysanthemums
- Bee balm
- Dianthus
- Liatris
- Penstemon
- Artemisia
- Ornamental grasses
For plants that bloom throughout spring and summer, dividing in early spring may also be an option. However, be sure to check the specific needs of each plant species, as some may recover better from division at different times of the year.
Exceptions: Perennials That Don't Like Being Divided
Some perennials resent being disturbed and should be divided only when absolutely necessary. Here are just a few examples:
- Peonies: Prefer to be left alone but can be divided in fall if needed.
- Baptisia: Develops deep roots and dislikes transplanting.
- Monkshood: Slow-growing and difficult to reestablish.
- Bleeding heart: Sensitive to root disturbance.
- Butterfly weed: Deep tap roots make it difficult to transplant.
If a plant is known to dislike division, but it's outgrowing its space or struggling, consider transplanting only a portion of the plant instead of disturbing the entire root system.
HOW TO DIVIDE PERENNIALS: STEP-BY-STEP GUIDE
Once you’ve determined when to divide perennials, follow these steps for successful division and replanting.
1. Choose the right day
- Divide on an overcast day to minimize transplant shock.
- Avoid dividing during extreme heat or drought conditions.
2. Prepare the plant
- Water the plant deeply a day before dividing to reduce stress and keep roots hydrated.
3. Dig up the clump
- Use a sharp spade or garden fork to dig around the plant’s root ball.
- Lift the entire clump carefully, keeping as much of the root system intact as possible.
4. Separate the sections
- Gently pull apart by hand or use a clean, sharp knife to cut through tough roots.
- Ensure each division has at least 3 to 5 healthy shoots and a strong root system.
5. Replant immediately
- Plant divisions at the same depth as before.
- Space them properly to prevent future overcrowding.
6. Water and mulch
- Water thoroughly after planting to help roots settle.
- Apply a layer of mulch to conserve moisture and protect roots.
Photo by: Jennifer McCallum / Shutterstock.
TIPS FOR SUCCESS WHEN DIVIDING PERENNIALS
- Rejuvenate soil: Mix in compost or organic matter before replanting.
- Skip fertilizer initially: Wait until new growth appears before feeding.
- Provide temporary shade: If the weather is hot, use light shading to prevent wilting.
- Keep divisions moist: Regular watering is crucial for establishment.
- Label your plants: If you’re dividing multiple perennials, marking them with plant tags can help you remember what’s where.
COMMON MISTAKES TO AVOID WHEN DIVIDING PERENNIALS
- Dividing too often: Some perennials only need division every 3-5 years.
- Waiting too late in the season: Avoid dividing right before harsh weather.
- Planting divisions too deep or too shallow: Keep them at the original depth.
- Letting roots dry out: Always replant as soon as possible.
- Overwatering immediately after division: While keeping plants hydrated is crucial, excessive watering can cause root rot. Water regularly but allow soil to drain properly.
Knowing how to divide perennials properly ensures healthier plants, more abundant blooms, and a thriving garden. By following the guidelines and knowing when to divide perennials—fall for spring bloomers and spring for fall bloomers—you can improve plant health and maximize your garden’s potential.
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