How to Divide Overgrown Perennials

Perennials bloom year after year, but over time, the plants may get crowded and the flowers won't appear as strong or full as they used to. When your perennials start producing weaker blooms, it may be time to divide the roots and separate them into multiple plants. When you divide your plants, all you need to do is dig up the root ball and cut it into smaller sections before you replant them. With a little bit of work, your garden will look beautiful again!

Part 1

Part 1 of 3:

Choosing When to Divide Perennials

1
Divide your plants every 3-5 years after planting them. Unlike annual blooms, perennials produce new shoots every year and continue to grow larger. After 3-5 years, your perennials will start to crowd their planting area and make it difficult for them to receive nutrients. Keep track of how long you've had your plants so you know when they're ready to transplant.^{[1]XResearch source}
- Note when you add a new plant to your garden or landscaping so you can remember when you need to divide them.
- Watch your plants to see if they have weak growths, fewer flowers, or a thin/bare spot in the center of the clump, since these may be signs that you need to divide your plants.
2
Work on fall blooms in the spring so they have time to grow before blooming. Dividing perennial plants works best either before or after their blooming season since they're dormant. If you have perennials that fully bloom late in the summer or early in fall, choose a day in early spring to make your divisions so the roots can establish themselves and make your plant stronger. Check that there are no risks of frost or ice before you start planting or else smaller divisions may not survive.^{[2]XResearch source}
- Some examples of fall blooms include mums, goldenrod, daylilies, aster, and sedum.^{[3]XResearch source}
- Look online for when the last expected freeze occurs in your area so you know when to start dividing your plants.^{[4]XResearch source}
Tip: The perennials may not have strong blooms the year that you divide them, but they will usually get stronger the following year.
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3
Split spring blooms in the fall so they have time to recover before next season. Spring blooms don't have enough time to establish their roots if they're divided right before their bloom. Plan on starting your divisions in the later summer or early fall months so the roots have enough time to grow and recover before the next bloom. Make sure you plant at least 6 weeks before the first frost in your area or else weaker divisions may not survive.^{[5]XResearch source}
- Spring blooms include plants like peonies, daisies, irises, and hostas.^{[6]XResearch source}
- Check online to find out when to expect the first frost in your area.^{[7]XResearch source}
The heat of the sun can harm and stress your plants if you choose to divide them on a clear day. Check the weather forecast for your area and choose a mild, cloudy day so you can work without damaging your plants. If there aren't any overcast days and you need to divide your plants, pick the mildest day to do the work.^{[8]XResearch source}
5
Water your perennials the day before you plan on dividing them. Fill up a watering can and thoroughly water your plant and the area around it. The water helps loosen the soil and helps your plant survive once you remove it from the ground. Keep watering until the soil 1–2 inches (2.5–5.1 cm) below the surface is wet to the touch.^{[9]XResearch source}
- Don't overwater your plants so there's standing water around them since it could cause them to get waterlogged and unhealthy.
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Part 2

Part 2 of 3:

Splitting the Root Ball

1
Push a shovel into the ground 6 inches (15 cm) away from your plant. Measure at least 6 inches (15 cm) out from the main growth on your plant. Drive the blade of your shovel vertically into the ground, and pull the handle back toward you to rock the dirt up and down. Once you loosen the dirt in the first spot, pull your shovel out of the ground.^{[10]XResearch source}
- Be careful of other plants in the area so you don't accidentally cut their roots or affect their growth.
- If you're dividing spreading perennials, such as gooseneck and bee balm, or woody perennials, like lavender and rosemary, you only have to dig up the section you want to divide. For other perennials, it's easier to remove the entire plant from the ground.
2
Work your shovel around the plant in a circle to lift it out of the ground. Move the blade of your shovel to either side of where you just placed it and push it into the ground again. Continue working the shovel back and forth around the plant until you make a full circle. When you go once around the perennial, the dirt should be loose enough for you to lift it up and out of the ground with your shovel.^{[11]XResearch source}
- If you can't lift up the plant after going around it with your shovel once, try loosening the dirt a second time.
3
Separate the stems so each section has 3-5 shoots. Once you have the plant out of the ground, collect the shoots or stems growing from it and separate them into sections. Make sure each section you make has at least 3-5 shoots in the same portion of the main root ball so you can see where to make your divisions. Aim to have about 3-4 sections of shoots that are about 3 inches (7.6 cm) in diameter when you're finished.^{[12]XResearch source}
- Wear gardening gloves while you work so you don't have any reactions to plant sap or fertilizers in the soil.
- Remove any weak stems that your plant has while you're dividing it so you don't replant a weak growth.
4
Cut through the root ball with a knife to divide the plant. Set the root ball down on a hard, steady surface and push the knife into it to cut out your sections. Be careful since the root ball may be hard to cut through and your knife could slip. Make sure each section has a large clump of roots attached to it or else it may be difficult to support the new growth.^{[13]XResearch source}
- If you need to separate larger perennial plants, you may need to pry them apart with gardening forks or even use an ax to chop it.
- You do not need to divide the root ball for spreading and woody perennials since you've already removed individual plants.
Tip: Sanitize your knife with a disinfectant spray or isopropyl alcohol after each plant so you don't accidentally spread any bacteria or diseases between them.^{[14]XResearch source}
5
Tease the roots out from each of your new divisions. Once you have the root ball separated into different sections, gently pull the roots so they extend down and out from the plant. Don't try to force any roots to move since they could break and make your plant weaker. Try to spread the roots as much as you can without damaging them so they can get the most nutrients from the soil.^{[15]XResearch source}
- Cut off any weak or broken roots immediately so they don't develop rot or make your plant die.
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Part 3

Part 3 of 3:

Transplanting Your Divisions

1
Dig a new hole that's 2–3 in (5.1–7.6 cm) wider than the root ball. Find a place to put your plant with a similar amount of sun throughout the day as the old location. Check that the area is well-drained so your plant doesn't get overwatered. Make sure the hole is the same depth as the root ball and is 2–3 inches (5.1–7.6 cm) wider on each side so it has space to grow.^{[16]XResearch source}
- You can also transplant divisions into a flower pot if you want to have a houseplant.
Tip: If you don't plan on replanting your divisions right away, keep the roots submerged in water in a shady place until you're ready to replant them.
2
Amend the soil with compost or fertilizer where you're planting the divisions. Put a ¹⁄₄–¹⁄₂ in (0.64–1.27 cm) layer of compost at the bottom of the hole you just dug so your new plant can get nutrients while it starts growing again. If you don't have compost, use a 0-19-0 fertilizer or bone meal to help promote healthy root growth for your plants. Follow the directions carefully on the packaging so you don't harm your plants.^{[17]XResearch source}
- Too much fertilizer can “burn” your plants and damage them.
- Wear gardening gloves while working with fertilizer so you don't get any skin irritation.
Place the division you cut in the middle of the hole you dug out and press it down gently so it stays in place. Backfill the soil back into the hole, tamping it down with your hand or your shovel occasionally so it comes into contact with the plant's roots. Make a small mound of dirt around the main shoots when the hole is filled in so water doesn't pool there.^{[18]XResearch source}
4
Water the plants as soon as the hole is filled in. Use your watering can or a sprinkler to water the transplant thoroughly. The water helps promote new growth from the plant and helps compact the soil around it. When the soil 2 inches (5.1 cm) down is moist to the touch, then you can stop watering.^{[19]XResearch source}
- Continue watering the plant every other day for the next 2-3 weeks so it stays hydrated and promotes healthy growth.^{[20]XResearch source}
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Tips

Prune your plants regularly to control new growths and make it easier to divide your plants later on.
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Give divided perennials as gifts if you don't have room in your yard or home to keep them.
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