Astilbe Astilbe spp. |
Spring, Fall |
Clump |
Divide in early spring or after it stops blooming in late summer to early fall; will bloom better with division every 2 to 3 years |
| Bachelor’s button Centaurea montana |
Spring, Fall |
Clump |
Easy to divide; needs to be divided every 1 to 2 years to keep plants vigorous |
Bearded iris Iris hybrids |
Summer |
Rhizome |
Divide in summer when flowering is over, at least 6 weeks before frost so plants have time to get established |
Bee balm Monarda spp. |
Spring, Summer |
Rhizome |
Spreads quickly; easy to divide; for ease of handling, divide in spring as foliage is emerging |
Black-eyed Susan Rudbeckia spp. |
Spring, Fall |
Clump |
Easy to divide; divide every 3 to 4 years; for best appearance next season, don’t make divisions too small |
Blanket flower Gaillardia x grandiflora |
Spring, Fall |
Clump |
Easy to divide; roots usually pull apart easily by hand; divide every 3 to 4 years |
Bleeding heart, old-fashioned Lamprocapnos spectabilis |
Spring, Summer, Fall |
Clump |
Divide as foliage goes dormant in the heat or mark plant location; roots are brittle, handle carefully |
| Brunnera Brunnera macrophylla |
Spring, Summer |
Clump |
Divide in late spring to early summer, after blooming; will reseed but divide to keep specific cultivars true |
Bugleweed Ajuga reptans |
Spring, Summer, Fall |
Clump, spreads by stolons |
Plants root as they spread; no need to dig whole plant; cut off rooted outer pieces and replant |
Butterfly weed Asclepias tuberosa |
Spring |
Clump |
Difficult to divide because of taproot; for best results, purchase new plants |
Catmint Nepeta x faassenii |
Spring, Summer |
Clump |
Doesn’t need division often; cut back whole plant by half so roots have less foliage to support |
Columbine Aquilegia hybrids |
Summer, Fall |
Woody crown |
Divide every few years to keep this short-lived perennial around; reseeds but seedlings may not look like parent plants |
Coneflower Echinacea purpurea hybrids |
Spring, Summer, Fall |
Clump |
Easy to divide; divide every 4 to 5 years for healthier plants; reseeds and seedlings are easy to transplant |
Coral bells Heuchera hybrids |
Spring, Summer, Fall |
Woody crown |
Don’t worry about getting roots with each piece, they’ll sprout from the stem; cut individual leaves back by half to conserve moisture |
Coreopsis Coreopsis grandiflora |
Spring, Summer |
Clump |
Division every 3 to 4 years helps this short-lived perennial stay around longer; cut plant back by half |
Daylily Hemerocallis hybrids |
Spring, Summer, Fall |
Clump |
Divide every 5 to 7 years; rebloomers are best lifted in spring before they flower |
Delphinium Delphinium spp. |
Spring |
Clump |
Blooms best if divided down into small sections; division every 2 to 3 years will prolong plants’ life |
Dianthus Dianthus spp. |
Spring, Summer |
Clump |
Mat-forming types root as they grow; cut a rooted piece from the edge and replant |
European wild ginger Asarum europaeum |
Spring, Summer, Fall |
Rhizome |
Easy to dig and split; likes moist to wet soils, so keep new plants well watered |
Fall anemone Anemone spp. |
Spring |
Woody crown, spreads by runners |
Doesn’t like to have main clump disturbed; sends out underground runners so dig small new plants around the edges to transplant |
False indigo Baptisia australis |
Spring |
Clump |
Difficult to divide because of taproot; for best results, purchase new plants; slow to recover from being moved |
Feather reed grass Calamagrostis acutiflora |
Spring |
Clump |
Divide in spring; lift clump and cut into sections; you may need a saw or hatchet to divide roots |
Garden mum Chrysanthemum hybrids |
Spring |
Woody crown |
Easy to divide; divide every 2 to 3 years to keep plants blooming and vigorous; discard dead central portion |
Garden phlox Phlox paniculata |
Spring, Summer, Fall |
Clump |
Divide every 3 years or when flowering diminishes; discard the woody center and plant the edge pieces |
Geranium, hardy Geranium spp. |
Spring, Summer, Fall |
Woody crown |
A ring of foliage around a dead center tells you it’s time to divide; usually every 3 to 4 years is sufficient |
Goat’s beard Aruncus dioicus |
Spring |
Clump |
Rarely needs to be divided; tough roots make dividing difficult; leave plenty of room around new transplants because the plant gets large |
Goldenrod Solidago spp. |
Spring, Fall |
Clump |
Divide every 3 to 5 years to keep plants vigorous |
Hellebore Helleborus spp. |
Spring |
Clump |
Rarely needs to be divided; if you do divide it, do it in early spring while plants are in bloom or right after they stop flowering |
Hosta Hosta hybrids |
Spring, Summer, Fall |
Clump |
Easy to divide in early spring when foliage is emerging; dividing large clumps later won’t harm plants but leaves them lopsided for the summer |
Japanese painted fern Athyrium niponicum pictum |
Spring, Fall |
Clump |
Rarely needs to be divided, so divide only for new plants, every 7 to 8 years |
Joe-Pye weed Eupatorium purpureum |
Spring, Fall |
Woody crown |
Divide in early spring for easy handling; for fall division, cut back flowers; may need a saw or hatchet to cut apart woody crown |
Lady’s mantle Alchemilla mollis |
Spring, Fall |
Clump |
Divide in spring or fall; easiest in early spring as leaves begin to emerge; doesn’t need frequent division |
Lamb’s ear Stachys byzantina |
Spring, Summer, Fall |
Clump |
This hardy plant roots along the stem; cut a piece off the edge and replant; cut leaves back by half; don’t overwater |
Lily-of-the-valley Convallaria majalis |
Spring, Summer, Fall |
Rhizome |
Rhizomes pull apart easily; make sure each new division has a leaf and a cluster of roots |
Lungwort Pulmonaria hybrids |
Summer, Fall |
Clump |
Big leaves wilt easily; cut each leaf back by half and keep summer transplants well watered |
Maiden grass Miscanthus spp. |
Spring |
Clump |
Divide in early spring; use a hatchet or saw to cut clump apart; can dig whole clump to divide or chop out segments |
Oriental poppy Papaver orientale |
Summer |
Woody crown |
Divide in midsummer; foliage goes dormant quickly after flowering so mark the plant’s location; keep new transplants watered |
Peony Paeonia spp. |
Summer, Fall |
Clump |
New plants will take a few years to flower; set new plants at same depth as they were previously or they won’t bloom; keep watered; does not need to be divided often |
Russian sage Perovskia atriplicifolia |
Spring |
Woody crown |
Very difficult to divide because of taproot; for best results, purchase new plants |
Salvia Salvia spp. |
Spring, Fall |
Clump |
Divide every 5 or 6 years or when plant dies out in the center |
Sedum (tall) Sedum spp. |
Spring, Summer, Fall |
Clump |
Easiest to divide in spring when foliage is still small; dividing clumps later won’t harm plant but may reduce bloom for the year |
Shasta daisy Leucanthemum x superbum |
Spring, Summer, Fall |
Clump |
Easiest to divide in spring when foliage is still small; dividing clumps later won’t harm plant but will reduce bloom and leave plants lopsided for the year |
Speedwell Veronica hybrids |
Spring, Summer |
Clump |
Easy to slice into pieces; make sure to get plenty of roots with each new section |
Turtlehead Chelone lyonii |
Spring, Fall |
Clump |
Divide every 4 years or as needed; if you divide in fall, wait until the plant is done flowering |
Yarrow Achillea spp. |
Spring, Summer |
Clump |
Easy to divide; most types spread quickly so divide every 2 to 3 years |