6 Plants You Should Divide in Fall for a Lush Garden by Spring

Peony

It's hard to compete with the sheer beauty of a row of blooming peonies (Paeonia). Even when those flowers are a distant memory, it's wise to think about expanding your garden by dividing your favorites during fall.

"Dig up the clump and split it up into root divisions," says author Kathy Jentz. "Plant them with the tips of the roots pointed downward and the eyes set just below the surface of the soil."

She suggests amending the planting hole with peat and then mulching it over very lightly with leaf compost. "Don't add in any fertilizer," she adds.

• Zones: 3 to 9
• Size: Approximately 3 feet tall x 3 feet wide
• Care requirements: Full sun; moderate water; rich, well-drained soil

Siberian Iris

These irises (Iris siberica) like to slowly spread, and keeping them in check is a long-term garden project. "One surefire sign is when the clump is wide, but has a reduced number of blooms," says Teri Speight, landscape gardener and author.

She and Jentz agree that iris plants need to be divided every three to five years. "The best time is during the late summer or early fall," says Jentz. "When you plant the new divisions, be sure the soil level is just to the top of the rhizomes, and not burying them."

She explains that the foliage stays evergreen most of the year, so you'll have some annual maintenance. "In the fall, you can trim back any brown or floppy leaves or fans," she says. "Clearing out this dead foliage can prevent the dreaded iris borer from wintering over in the plants."

• Zones: 3 to 9
• Size: Varies: 12 to 36 inches tall x 24 inches wide
• Care requirements: Full sun; well-drained soil

Coneflower

The gorgeous coneflower (Echinacea spp.) brings so much visual interest to the garden, and it's wise to occasionally divide it to keep the plant healthy and vibrant.

You won't need to do this every year, but it's good to do every few years. Just dig up the root ball and divide it into smaller pieces, then replant.

• Zones: 3 to 9
• Mature size: 24 to 48 inches tall x 24 inches wide
• Care requirements: Full sun, well-drained soil

Tall Garden Phlox

You can expect a long bloom time for Phlox paniculata—it will often stay flowering for much of the summer, depending on the climate. Division is a simple matter.

"Dig up the clump in fall, then loosen the root ball and gently pull it apart into sections with roots and stems attached," says Jentz. "Then replant the sections into amended planting holes right away. Plant them at the same depth as the original was in the soil."

• Zones: 3 to 8
• Size: 24 to 48 inches tall x 24 to 36 inches wide
• Care requirements: Full to partial sun; moist soil

Daylily

Despite the relatively short bloom time of each individual flower, daylilies (Hemerocallis) produce no shortage of blooms during the summer, making them an excellent choice for long-lasting color and interest during the growing season.

Fall is the best time to cut the foliage, divide, and then replant them. "If the clump is large, a shovel will aid in dividing the clump," says Speight. "Take note of what color or cultivar this plant is throughout the bloom time to add color and foliage where you want it. I use my favorite daylilies as place holders when I have gaps in the garden."

• Zones: 3 to 9
• Size: 24 to 48 inches tall x 24 to 36 inches wide
• Care requirements: Full to partial sun; well-drained soil

Yarrow

Known for its wispy, fern-like foliage and delicate blossoms, Achillea millefolium can be planted as a statement piece around garden borders and used as a deer deterrent.

"It's easy to dig up and divide," says Speight. "I use my hori hori knife to dig the shallow roots, then I pull them apart by hand and replant. Without fail, the next season's blooms are quite prolific."

• Zones: 3 to 9
• Size: 2 to 3 feet tall x 8 to 12 inches wide
• Care requirements: Full sun; well-drained soil