13 Perennials You Shouldn’t Divide

Learn which perennials are best left alone when it comes to division.

Photo By: PerennialResource.com

Photo By: PerennialResource.com

Photo By: Julie Martens Forney

Photo By: PerennialResource.com

Photo By: PerennialResource.com

Photo By: PerennialResource.com

Photo By: PerennialResource.com

Photo By: PerennialResource.com

Photo By: PerennialResource.com

Photo By: PerennialResource.com

Photo By: Image courtesy of northscaping.com

Photo By: PerennialResource.com

Photo By: PerennialResource.com

Lupine (Lupinus Popsicle Series Mixed)

In areas with cool summers, lupines are a prized perennial that attract butterflies and hummingbirds. The secret to beautiful lupines is rich, slightly acid soil that drains well. This is a deep, tap-rooted perennial that doesn’t respond well to division or disturbance. Instead, allow plants to set seed. Seedlings don’t always come true to parent plants, so you might be surprised by the flower colors you see. Plants are hardy in Zones 4 to 6.

'Munstead' Lavender (Lavandula angustifolia ‘Munstead’)

Lavender is actually a woody shrub, which means it won’t respond well to division—your divisions will likely die. Instead, look around the plant for stems that might have layered. Layering occurs when branches that touch soil develop roots. Cut the branch between the main plant and the layered seedling, dig up the seedling and treat it like a division. 'Munstead' is one of the hardiest lavenders —plants survive winters in Zones 5 to 9.

Peony (Paeonia spp.)

Peonies are a perennial that stands in the garden from generation to generation without missing a blooming beat. Dividing this perennial isn’t recommended. If you must undertake the task, do it in fall and be sure to get at least three growing points or eyes with each division. More eyes per division are better. Peonies are hardy in Zones 3 to 8.

Red Hot Poker (Kniphofia ‘First Sunrise’)

Spikes of blazing blooms in tones of red, orange and gold earn red hot poker its name. These perennials are conversation starters in the garden. Plants have narrow, evergreen foliage and are hardy in Zones 5 to 9. ‘First Sunrise’ is an early-blooming variety—an ideal size for smaller modern gardens. Hummingbirds love the blossoms. Division doesn’t usually go well. Try to lift pups or smaller plants from near the mother clump instead.

Festival Star Baby’s Breath (Gypsophila paniculata ‘Danfestar’)

Prized in floral arrangements, baby’s breath forms a flowery cloud in the garden. This perennial produces a long taproot, which makes division very difficult, if not impossible. Trim plants back in spring before new growth starts. Count on baby’s breath as a filler in perennial gardens. This variety is shorter, topping out at 12 to 18 inches. It’s a perfect choice for growing near the front of a flower border. Baby’s breath is hardy in Zones 3 to 9.

Columbine (Aquilegia x caerulea ‘Sunshine’)

Fully double yellow blooms make this columbine resemble a living ray of sunshine in the garden. Plants flower in late spring to early summer and are rabbit-resistant. Columbine typically self-sows if blooms are allowed to set seed. This is the easiest way to propagate this perennial. Dividing mature plants doesn’t work. Columbine is hardy in Zones 3 to 9.

Oriental Poppy (Papaver orientalis ‘Flamenco Dancer’)

'Flamenco Dancer' poppy unfurls 4- to 6-inch-wide red blossoms with a deep black center in late spring to early summer. Poppies steal the show when they’re in full bloom, but later plants go dormant. Tuck other perennials around these bloomers to avoid bare spots in the garden. Oriental poppies form long taproots that resemble white carrots. Dividing isn’t always successful and is not typically recommended. Plants are hardy in Zones 3 to 7.

Goat’s Beard (Aruncus dioicus)

For the partial shade garden, it’s tough to beat the feathery flowers of goat’s beard. This summer bloomer opens flower spikes up to 12 inches long. Plants are pest-free, deer-resistant and hardy in Zones 3 to 7. Place goat’s beard where you want it—plants form thick roots that often require a saw to cut. It’s best not to plan on dividing this shade-loving plant. Look for young shoots around the mother plant and attempt to transplant those.

Swamp Milkweed (Asclepias incarnata)

A must in butterfly gardens, swamp milkweed is a host plant for monarch butterfly caterpillars. Butterfly adults visit blooms, along with many other pollinators. Flowers are typically pink, but you may spot some white blossoms on plants. Despite the name, swamp milkweed tolerates average to moist soils. This tap-rooted perennial prefers full sun and is best left undisturbed once planted in the garden. Swamp milkweed is hardy in Zones 3 to 6.

Blue False Indigo (Baptisia australis)

Beautiful purple flower spikes appear in late spring to early summer above blue-tinted leaves on this shrubby native. Blue false indigo can be slow to establish in the garden and dislikes being moved, so take time to site it carefully. Give plants full sun, and keep an eye out for caterpillars. Many butterflies use this plant as host food for their caterpillar larvae. False indigo is hardy in Zones 4 to 8.

'Little Gem' Candytuft (Iberis sempervirens ‘Little Gem’)

Candytuft is a spring star, cascading over stone walls and slopes with blooming abandon. Its snow-white flowers sparkle in spring sunshine. This ground cover is actually a type of woody shrub, which is why it doesn’t divide well. 'Little Gem' is smaller and grows more slowly than old-fashioned candytuft, making it a smart choice for low-maintenance modern landscapes. Plants are hardy in Zones 3 to 9.

Gas Plant (Dictamnus albus ‘Purpureus’)

From late spring to midsummer, gas plant earns its keep in the garden with pink flower spikes. Butterflies flock to blooms, but deer avoid this perennial because of its lemon-scented leaves. Plants are hardy in Zones 3 to 7. Gas plant forms a deep tap root that makes division difficult. Instead, dig up seedlings that form around the mother plant. Gas plant sap irritates skin, so wear gloves when working with this perennial.

Russian Sage (Perovskia atriplicifolia)

For tough-as-nails beauty from late summer to fall, try Russian sage. This perennial loves hot, dry, full sun conditions and creates a cloud of purple in the garden when it flowers. Plants are a woody perennial that doesn’t divide well. Instead transplant layered seedlings, plants that have formed where stems touched soil and rooted. Leaves and stems have a sagey scent, which makes them distasteful to rabbits and deer. Plants are hardy in Zones 4 to 9.

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