
Photo © Elaine Mills
Native perennials may benefit from periodic division to improve their vigor and appearance. Indications that a plant requires division are dead sections at the center of the clump, reduced size or abundance of flowers, or sparse foliage. Division can rejuvenate the plant and stimulate new growth. Perennials can also be divided for propagation purposes.
This table of common perennials indicates the root type of each plant, the best season for division (if appropriate), and specific advice on frequency and manner of division.
Perennial | Root Type | Season To Divide | Notes |
---|---|---|---|
Allegheny Spurge | Rhizomes | Late Summer | Spreads slowly, unlike invasive non-native P. terminalis Divide established clumps in August or September |
Anise Hyssop | Clumping | Spring | Divide every 3-4 years Make sure each section contains roots & top growth |
BeardtonguePenstemon digitalis | Clumping | Spring | Divide with spade or garden fork every 1-3 years |
Blazing Star | Corm | Spring | Divide every 4-5 years to keep plants vigorous |
Blue Vervain | Clumping | Early Fall | Divide with a spade after flowering |
Blue Wild Indigo | Taproot | Not suitable for division | Difficult to divide because of taproot Resents disturbance; slow to recover from being moved |
Blue-stemmed Goldenrod | Rhizomes | Spring | Spreads, but not aggressively Divide rhizomes |
Butterfly-weed | Taproot | Not suitable for division | Difficult to divide because of taproot Best to purchase additional plants |
Cardinal Flower | Clumping | Spring | Short-lived; allow to self-seed Remove young offsets from basal rosette of mature plant |
Coastal Plain Joe-pye-weed | Woody crown | Spring or Early Fall | Does not require frequent division for plant health Divide in early spring for easiest handling May need a saw or hatchet to cut apart woody crown |
Culver’s Root | Clumping | Spring or Late Fall | Divide every 4-5 years Be sure each rootstock segment has a bud |
Dwarf Crested Iris | Rhizomes | Early Fall | Divide every 3-4 years when leaves begin to turn yellow |
Eastern Blue-star | Clumping | Not suitable for division | Seldom needs division; divisions are slow to establish |
Eastern Prickly-pear | Clumping | Growing Season | Break off pads at joint; let them dry, and stick in prepared soil New roots form very quickly Use gloves to protect hands from barbed hairs (glochids) |
Eastern Red Columbine | Woody crown | Not suitable for division | Dislikes disturbance; short-lived but reseeds easily Moves about garden, favoring pathways and sidewalk cracks |
Foamflower | Clumping | Spring or Early Fall | Divide by hand |
Garden Phlox | Clumping | Spring or Late Summer | Divide every 2-4 years when flowering diminishes Discard woody center and replant edge pieces Regular division minimizes susceptibility to powdery mildew |
Golden Ragwort | Stolons | Early Spring | Self-seeds & spreads aggressively by stolons from central rosettes Divide in early March before flowering |
Great Blue Lobelia | Clumping | Spring | Short-lived; self-sows readily Remove young offsets from basal rosette of mature plant |
Great White Trillium | Rhizomes | Not suitable for division | Best left to experts; plants take 4-5 years to flower |
Green-and-Gold | Rhizomes | Late Spring | Spreads slowly by rhizomes |
Hairy Alumroot | Woody crown | Spring or Early Fall | May not get roots with each piece; they will sprout from stem Cut leaves back by half to conserve moisture |
Jacob’s Ladder | Clumping | Early Spring | Spreads slowly by self-seeding Divide clumps in early spring or late summer |
Large-flowered Bellwort | Clumping | Spring or Early Fall | Divide mature clumps |
Mayapple | Rhizomes | Fall | Colonizes by rhizomes Spring ephemeral; divide when dormant with at least one bud |
Moss Phlox | Spreading | Spring | Divide after flowering Branching prostrate stems can root at nodes Find center of growth to divide successfully |
New England Aster | Clumping | Spring | Divide every 3-5 years with soil knife, saw, or edge of shovel Make sure tool is sharp to avoid damaging roots |
New York Ironweed | Clumping | Spring | Divide large clumps with spade or garden fork |
Orange Coneflower | Spreading | Spring or Early Fall | Easy to divide with spade or garden fork; divide every 3-4 years For best appearance, don’t make divisions too small |
Oxeye | Clumping | Not suitable for division | Spreads by self-sowing; large clumps difficult to divide |
Partridge-berry | Spreading | Spring | Stems root when in contact with soil Cut 6- to 12-inch piece of trailing stem Carefully uproot to avoid breaking off small roots Plant in rich, well-drained site |
Purple Coneflower | Clumping | Spring or Early Fall | Easy to divide; divide every 4-5 years for healthier plants Cut crown apart with sharp knife |
Robin’s Plantain | Stolons | Spring | Self-seeds and spreads by stolons; divide linked plants |
Rough-stemmed Goldenrod | Rhizomes | Spring | Can spread aggressively; divide with spade or garden fork Divide every 3-5 years to keep plants vigorous |
Scarlet Beebalm | Rhizomes | Spring or Early Fall | Spreads quickly; easy to divide Easiest to divide in spring as foliage is emerging Discard old central clump Also pertains to Wild Bergamot (M. fistulosa) |
Short-toothed Mountain-mint | Rhizomes | Early Spring | Spreads rapidly (4-6 inches per year) Use spade to divide and extract shallow stems |
Solomon’s Seal | Rhizomes | Spring or Early Fall | Spreads slowly via rhizomes Leave several buds on each division |
Spiderwort | Clumping | Early Spring or Early Fall | Divide large clump into several pieces |
Swamp Milkweed | Clumping | Not suitable for division | Difficult to divide because of taproot Best to purchase additional plants |
Swamp Rose-mallow | Clumping | Spring | Divide clump into pieces with sufficient sprouts |
Threadleaf Coreopsis | Rhizomes | Spring or Early Fall | Short-lived; divide every 3-4 years Cut back plant by half |
Turk’s Cap Lily | Bulb | Spring | Plants spread via stoloniferous bulbs Gently twist offsets from bulb of mature plant to divide them Keep moist; plant in individual pots and transplant outdoors when 1-2 years old Make sure pointy ends face upwards |
Virginia Blue Flag | Rhizomes | Early Fall | Divide when leaves begin to turn yellow Keep stringy roots attached to stubby rhizome sections |
Virginia Bluebells | Rhizomes | Fall | Spring ephemeral; divide rhizomes while plant is dormant |
Virginia Knotweed | Rhizomes | Spring | Spreads rapidly by self-seeding & rhizomes Divide when dormant in spring |
White Turtlehead | Clumping | Spring | Divide every 4 years or as needed Easy to divide with spade; keep moist |
White Wood Aster | Rhizomes | Early Spring | Self-seeds and spreads vigorously by rhizomes Divide clumps or allow to spread on its own |
Wild Geranium | Rhizomes | Early Spring or Fall | Rhizomes form right angles, simplifying division |
Wild Ginger | Rhizomes | Early Fall | Spreads slowly; divide root of mature plants |
Wild Pink | Clumping | Spring | Spreads from ground-level stems Gently divide clumps in spring |
Wild Stonecrop | Spreading | Spring | Stems root at nodes to form new plants Gently dig up mature plant & carefully pull apart roots to separate into sections which quickly take root |
Woodland Phlox | Spreading | Spring or Early Fall | Shoots root at nodes; detach rooted stems into sections |
YarrowAchillea millefolium | Rhizome | Early Spring | Easy to divide; spreads quickly Divide every 2-3 years |