Many perennials need to be divided every few years to rejuvenate their growth and avoid crowded root systems, but not all perennials respond well to division.
Why Some Plants Don't Like Dividing (And What to Do Instead)
While plants like daylilies will get unruly if they aren’t divided every few years, some perennials have long taproots or sensitive root systems that may suffer if they’re moved around after planting.
Many gardeners are accustomed to dividing perennials in order to get additional plants for their garden, but if you happen to divide the wrong perennials, you may affect the growth of your plants or damage plants so severely that they won’t regrow!
In the list below, you’ll find 14 common perennials that don’t like to be divided…either in spring or in fall.
If you have any of these plants growing in your garden, skip plant division and spruce up your perennials with an annual application of mulch and/or compost instead. And if you typically propagate plants via root division, try propagating these plants from seeds or stem cuttings!
Jump to:
- Why Some Plants Don't Like Dividing (And What to Do Instead)
- 14 Perennials That Should Not Be Divided
- 1. Butterfly weed (Asclepias tuberosa)
- 2. Joe Pye weed (Eutrochium purpureum)
- 3. Evening primrose (Oenothera spp.)
- 4. False indigo (Baptisia spp.)
- 5. Baby’s breath (Gypsophila spp.)
- 6. Lupine (Lupinus spp.)
- 7. Lavender (Lavandula spp.)
- 8. Foxglove (Digitalis spp.)
- 9. Milkweed (Asclepias spp.)
- 10. Russian sage (Perovskia atriplicifolia)
- 11. Rosemary (Salvia rosmarinus)
- 12. Cushion spurge (Euphorbia epithymoides)
- 13. Candytuft (Iberis spp.)
- 14. Gas plant (Dictamnus albus)
- Frequently asked questions
- How do you cold-stratify seeds?
- What happens if you don't cold-stratify seeds?
- How long do stem cuttings take to root?
- Is it better to root cuttings in water or soil?
- What is the best time to divide perennials?
- What is the best tool for dividing perennials?
- Summary
14 Perennials That Should Not Be Divided
As with many gardening tasks, there is some flexibility with plant division, and some gardeners may have different experiences dividing specific plant species. The plants listed below generally don’t respond well to root disturbance, and dividing these plants is not advised, but that doesn’t mean that you absolutely CAN’T divide these plants!
Some gardeners may have already successfully divided some (or all) of the plants listed below, and it’s possible that these plants can potentially bounce back after root division. However, all of these perennials do have relatively sensitive root systems, and they are easier to propagate and manage using other plant care methods.
1. Butterfly weed (Asclepias tuberosa)
| Plant name: | Butterfly weed |
| Growing zone: | Zones 3 to 9 |
| Recommended plant propagation methods: | Seed, stem cuttings |
Butterfly weed is one of the best plants to grow in pollinator gardens since its tangerine orange flowers are simply irresistible to butterflies and other insects. But when you’re planting butterfly weed in your beds, choose your planting location carefully, as these plants don’t transplant well, and they generally shouldn’t be divided. If you want to propagate new butterfly weed plants, the best way to do it is by planting seeds in the fall or spring using the cold stratification method.
The main reason why butterfly weed doesn’t like to be transplanted or divided is due to the plant’s long tap root. Butterfly weed utilizes that long tap root to draw up moisture from deep within the soil, which helps this hardy plant resist drought-like conditions. But as anyone who’s ever tried to dig up a dandelion can tell you, tap roots, including butterfly weed taproots, are very sturdy, and they are tough to transplant!
2. Joe Pye weed (Eutrochium purpureum)
| Plant name: | Joe Pye weed |
| Growing zone: | Zone 4 to 9 |
| Recommended plant propagation methods: | Seed, stem cuttings |
Joe Pye weed can technically be transplanted and divided, but it’s not ideal. Like butterfly weed, Joe Pye weed has an extensive root system, which can be tricky to dig up, and if you do manage to dig these plants out of the soil, you’ll quickly note how heavy their roots are! On top of that, Joe Pye weed plants can grow over 10’ tall, and they can be very unwieldy to move about, especially if you don’t trim their stems down first.
If you do decide to divide Joe Pye weed plants, the best time to do it is either in spring or fall, when the weather is cool. However, this step may not be necessary if you locate your Joe Pye weed patch in an area of your garden where the plants will have plenty of room to grow. If you love your Joe Pye weed plants and want to get more plants for your garden for free, try gathering seeds from your Joe Pye weed in the fall and starting the seeds indoors or outdoors using cold stratification.
3. Evening primrose (Oenothera spp.)
| Plant name: | Evening primrose |
| Growing zone: | Zones 5 to 9 |
| Recommended plant propagation methods: | Seed |
There are about 145 different plants in the Oenothera genus, and they have different care requirements. Some types of evening primroses can tolerate root division, while other varieties, like Oenothera macrocarpa, don’t take kindly to having their roots disturbed. For this reason, if you want to divide the evening primroses growing in your garden, you may need to research the particular species you’re growing to see if plant division is recommended.
While you may not want to divide all varieties of evening primrose plants, you can easily grow more of these plants from seed. Evening primrose seeds should be directly sown in garden beds in either autumn or spring, as these plants produce long tap roots that don’t transplant well. Keep in mind that some evening primrose varieties are biennials, which means they only flower and produce seeds in their second year, and they will need to be replanted every two years unless you allow your plants to self-sow.
4. False indigo (Baptisia spp.)
| Plant name: | False indigo |
| Growing zone: | Zones 3 to 9 |
| Recommended plant propagation methods: | Seed, stem cuttings |
Like many other plants on this list, false indigo has a vigorous root system and a long, deep tap root, which makes successful plant division unlikely. While you can sometimes transplant or divide these plants, more often than not, false indigo tap roots will become damaged during the transplanting process, which will cause plants to struggle after they’ve been transplanted. Even if you don’t sever false indigo’s tap root, digging up that long root system can be a back-breaking chore that most gardeners will probably want to avoid if they can help it!
The good news is that false indigo plants often don’t need to be divided, and these plants are easy to propagate from seeds, too. False indigo plants produce seed pods in autumn, which can be harvested when the pods are dry and brittle, and the seeds inside rattle around easily. After picking the seed pods, plant false indigo seeds directly in your garden beds in autumn, and you should have new plants sprouting by spring!
5. Baby’s breath (Gypsophila spp.)
| Plant name: | Baby’s breath |
| Growing zone: | Zones 3 to 9 |
| Recommended plant propagation methods: | Seed, stem cuttings |
While some perennials can be flexible about root division, baby’s breath is not one of them. Baby’s breath is notoriously difficult to transplant, and dividing baby’s breath plants is usually an effort in futility. These delicate plants will usually fail quickly after transplanting, but you can propagate new baby’s breath plants in other ways.
Baby’s breath seeds can be collected after the plant finishes flowering, and then they can be directly sown in your garden beds after the first fall frost. Another option is to plant baby’s breath seeds indoors in spring, or you can propagate these plants from stem cuttings by dipping the cuttings in rooting hormone before planting them in potting mix. If you love making homemade bouquets, growing baby’s breath is a definite must-do… just skip plant division!
6. Lupine (Lupinus spp.)
| Plant name: | Lupine |
| Growing zone: | Zones 3 to 8 |
| Recommended plant propagation methods: | Seed, stem cuttings |
Lupines are the stars of spring gardens, and they’re famed for their eye-catching, spire-shaped flowers that come in shades of blue, purple, pink, and white. A brilliant pollinator plant, lupines look best when they’re planted in mass planting arrangements, which makes their flower colors come alive. However, if you want to get more lupine plants for your garden, dividing lupine roots is not the way to go about it!
Lupines have long tap roots, and if that root system gets damaged during transplanting or plant division, there is very little chance that the lupine plant will recover. To avoid this, most gardeners grow lupines from seed or from stem cuttings, but lupines also readily self-sow if you don’t remove their seed pods. If you’re growing lupines from seed, you’ll often get better germination rates if you scarify or soak the seeds prior to planting.
7. Lavender (Lavandula spp.)
| Plant name: | Lavender |
| Growing zone: | Zones 5 to 9, depending on variety |
| Recommended plant propagation methods: | Stem cuttings |
Lavender is one of the most popular plants to grow in home gardens, and it’s prized as both an ornamental and an edible. English lavender is the most popular lavender to use in cooking, and it can be steeped into teas or baked into desserts, while other lavender varieties can be used to make crafts like dried lavender bouquets and scented eye pillows. Not to mention, bees and other pollinators love lavender flowers too!
With all of those charms, it’s no wonder why many gardeners want to divide their lavender to get more plants, but this is not a good idea. Lavender is a woody, shrub-like plant, and if you cut it down the middle when dividing, you’ll likely kill the plant off! Growing lavender from seed is often tricky, too; however, if you take stem cuttings and propagate them in soil with rooting hormone, you’ll end up with plenty of new lavender plants in no time flat.
8. Foxglove (Digitalis spp.)
| Plant name: | Foxglove |
| Growing zone: | Zones 3 to 10 |
| Recommended plant propagation methods: | Seed |
There are about 20 different species of foxgloves, and some of them adapt better to plant division than others. Perennial types of foxglove are easy enough to divide, and these plants can be dug up in autumn and divided with either gardening forks or a spade. However, biennial-type foxgloves do not like to be disturbed, and dividing these plants will often interrupt their short flowering cycle.
One of the most common types of foxgloves, Digitalis purpurea, falls into the biennial category. But while root division is best avoided with this foxglove species, you can easily propagate new biennial foxgloves from seeds! As with evening primrose, biennial foxgloves focus on leaf and root development during their first year, and then they flower and produce seeds during their second year.
9. Milkweed (Asclepias spp.)
| Plant name: | Milkweed |
| Growing zone: | Zones 4 to 9, depending on variety |
| Recommended plant propagation methods: | Seed, stem cuttings |
Butterfly weed is a type of milkweed, so it’s no surprise that both milkweed and butterfly weed have ended up on this list. Like butterfly weed, milkweed has a deep tap root system, which the plant utilizes to conserve moisture and resist drought. But while that tap root has its perks, it doesn’t make dividing and transplanting milkweed easy!
Young milkweed plants can often be transplanted just fine, but established plants should be left alone if you can help them. Milkweed patches tend to self-seed and spread on their own, but you can always gather milkweed seeds in autumn to start a new generation of plants. When harvesting milkweed seeds, you’ll know milkweed pods are ready to pick when they pop open with the slightest pressure from your fingers (it’s okay if they’re still green!)
10. Russian sage (Perovskia atriplicifolia)
| Plant name: | Russian sage |
| Growing zone: | Zones 4 to 9 |
| Recommended plant propagation methods: | Stem cuttings |
Some people have success dividing Russian sage, but it’s generally not recommended. With its woody stems and intense root system, Russian sage can be difficult to divide, and plants often don’t take after transplanting. If you do want to try your hand at dividing Russian sage, the best time to do it is in spring, when the weather is still cool.
Because Russian sage plants are tough to transplant, many growers propagate these plants from stem cuttings. If you want to go this route, take cuttings from healthy, tender stems and use a bit of rooting hormone to speed up the rooting rate. Russian sage can also be grown from seed, but this has unpredictable results, and germination time can vary anywhere from 21 to 120 days!
11. Rosemary (Salvia rosmarinus)
| Plant name: | Rosemary |
| Growing zone: | Zones 7 to 10 |
| Recommended plant propagation methods: | Stem cuttings |
Like lavender, rosemary is a woody shrub that can be damaged badly and even killed if you attempt to split it apart. While rosemary does respond well to pruning and trimming, maintenance for this plant should be conservative as rosemary plants only produce leaves and flowers on new wood. Cutting rosemary plants back into the woody sections will cause rosemary to stop growing.
If you want more rosemary plants, you can technically grow rosemary from seed, but this yields variable germination results, and plants will take a long time to reach a harvestable size.
An easier way to get new rosemary plants fast is to cut off a few healthy plant stems and propagate them in the soil. To improve the chances that your rosemary cuttings will produce roots, keep them potted in consistently moist soil and place a humidity dome or clear plastic bag over the cuttings to lock in humidity levels and keep the soil from drying out.
12. Cushion spurge (Euphorbia epithymoides)
| Plant name: | Cushion spurge |
| Growing zone: | Zones 3 to 10 |
| Recommended plant propagation methods: | Seed, stem cuttings |
Cushion spurge and other members of the Euphorbia family don’t like to be disturbed once they’ve become established, so it’s best to choose a planting spot and stick to it. However, young plants can be transplanted if needed, and you can try to divide established plants if you have to, but it may not always be successful. The best time to divide spurge plants is in early spring or fall, and plants should be watered in well after they’ve been planted, which will help them to settle into gardens more easily.
Although division is sometimes successful with spurge plants, a better way to propagate spurge plants is through stem cuttings. Cuttings should always be taken with sterilized pruners, as this will limit the chances that fungi or bacteria will spread into your cut plant stems. Beyond stem cuttings, you can also propagate spurge plants through seeds, or you can allow your plants to naturally seed themselves by not deadheading spent blooms.
13. Candytuft (Iberis spp.)
| Plant name: | Candytuft |
| Growing zone: | Zones 3 to 9 |
| Recommended plant propagation methods: | Seed, stem cuttings |
Candytuft can sometimes be divided by root division, but it isn’t the best idea. Many types of candytuft plants are classified as subshrubs, and they don’t like to have their roots disturbed. However, if you do divide these plants, it’s best to do it in the fall before the plant enters a state of dormancy.
While candytuft plants are more amenable to root division than some of the other species on this list, you’ll often get better results if you propagate candytuft either through stem cuttings or seeds.
Seeds can be collected after the plant’s flowers fade; however, most of the time, seeds don’t “come true” to the parent plant, and you may end up with seedlings with unexpected characteristics. Stem cuttings are often the most reliable way to propagate candytuft, but cuttings can take a while to root.
14. Gas plant (Dictamnus albus)
| Plant name: | Gas plant |
| Growing zone: | Zones 3 to 8 |
| Recommended plant propagation methods: | Seed |
Gas plants are an unusual choice for gardens as these plants contain flammable oils, which can make their stems and leaves spontaneously burst into flames on hot days! While this often doesn’t damage the gas plant itself, that sharp burst of flame can sometimes spread to nearby plantings and cause a fire. As a result, gas plants are not good choices for fire-prone areas, and they shouldn’t be grown directly beside homes or other buildings.
But while gas plants have their hazards, they are striking specimens that find their way into gardens from time to time. If you do have gas plants growing in your landscape and want to produce more of them, you will have the best luck propagating these plants from seed. Gas plants don’t like to have their roots disturbed, and plant division and transplanting is not advised with this species.
Frequently asked questions
How do you cold-stratify seeds?
Seeds can be stratified either indoors or outdoors in fall or spring. For fall plantings, sow seeds outdoors in prepared garden beds in late autumn, and they will overwinter and germinate in spring. For spring plantings, place seeds in a moist paper towel inside a Ziploc bag and pop them into your fridge for weeks before planting the seeds in pots or in your garden.
What happens if you don't cold-stratify seeds?
Many perennial seeds don’t need to be stratified, and if seeds do need to be stratified, they may still germinate even without that cold and moist period of dormancy. However, if cold stratification is recommended for a plant species and you don’t stratify those seeds, you may experience low germination rates.
How long do stem cuttings take to root?
Stem cuttings from tender stemmed plants may root in just a week or two, but rooting times can vary significantly between plant species. Plants with woody stems generally take the longest to form roots, and some of these plants may take a month or two to start rooting. When rooting cuttings in soil, you can speed this process along by dipping cut stem ends in rooting hormone before planting them.
Is it better to root cuttings in water or soil?
That depends. Plants with tender stems will often root readily in water, while woody-stemmed plants root more easily in soil.
What is the best time to divide perennials?
Some perennials fare better if you divide them in fall, while other perennials prefer to be divided in spring, and some perennials don’t want to be divided at all! A good rule of thumb to follow is that plants that bloom in spring should be divided in fall, and plants that bloom in fall should be divided in spring, but this rule doesn’t hold true for all types of plants.
What is the best tool for dividing perennials?
Perennials with loose root systems can often be divided by hand by gently teasing the roots apart with your fingers. For plants with tough and dense root systems, it’s usually best to cut the root ball apart with a spade or to pry the root ball apart with a pair of gardening forks.
Summary
If you’ve been gardening for any length of time, you know that gardening is sometimes not an exact science. While some growers may have success dividing certain plants, other gardeners may struggle to divide their plants every year. And much of this has to do with the growing requirements and root structures of the plants themselves.
Some plants have adaptable root systems, while plants with tap roots generally don’t like to be disturbed once they’ve become established. Although plant division is sometimes still successful, it can be touch and go, and you may have better luck propagating perennials using other propagation methods. In the end, it’s up to you how you choose to propagate your plants, but if you want to boost propagation rates, seeds, and stem cuttings may be the best choice with the plants we’ve covered today!
For more plant propagation tips, we have a full guide on rooting plant cuttings in water here, and you can also learn more about saving seeds from perennial plants in this easy guide.
Charmin
Kudos for giving the botanical names. Often the common name in English can be the common name for other plants as well.
Sherry
My primary rhododendron flowered well in spring. But during summer developed a black coating on trunk and branches, like it was in a fire. We had an unusually wet spring. Would that be why? Will it be okay next spring?
Mary Ward
That could be why. There's a good likelihood it is a fungal disease, which of course would be more probable in a wet year. It could also be the result of insect infestations. There are a few things that can present this way. You may want to do some research online. It might be a good idea to spray it with Neem oil, which will control many insects and also fungal diseases.
Sherry
Sherry: I love in West Michigan.