False sunflower | Heliopsis helianthoides | 5 to 10 years | Spring or fall | Cut crown apart with sharp knife. Discard old central portion. |
Flax | Linum perenne | Rarely; every 10+ years | Spring or early fall | Difficult to re-establish after division. Dividing long, tangled roots is also difficult. |
Foamflower | Tiarella wherryi | 1 to 3 years | Spring or fall | Divide by hand. |
Forget-me-not | Myosotis spp. | Annually; as needed | Spring | Transplant new planbts in spring. Divide by hand. |
Gas plant | Dictamnus albus | Rarely; every 10+ years | Spring | Divisions are difficult due to crown damage. A spade plunged straight down through the plant's center, cutting the roots cleanly without severe bruising gives best results. CAUTION: Wear gloves as contact may cause dermatitis. |
Globe flower | Trollius chinensis | Annually; as needed | Fall | Slow to recover after transplanting. |
Globe thistle | Echinops ritro | 6 to 10 years | Spring or fall | Difficult to re-establish. |
Goat's beard | Aruncus dioicus | Rarely; every 10+ years | Spring or fall | Does not re-establish easily after division due to a deep rootstock. Use knife to cut woody crown. |
Golden dead nettle | Lamiastrum galeobdolen | Annually; as needed | Spring or fall | |
Goldenrod | Solidago spp. | 4 to 5 years | Spring or fall | Divide with spade or pitchfork. |
Hen & chicks | Sempervivum tectorum | Annually; as needed | Spring or fall | Separate small outer rosettes from parent plant. |
Hollyhock mallow | Malva alcea 'Fastigiata' | 1 to 3 years | Spring or fall | |
Hosta | Hosta spp. | 6 to 10 years | Spring or fall | If center of plant begins to get bare, cut out center and discard. |
Hyssop | Hyssopus officianalis | Annually; as needed | Spring | Dig up and carefully divide woody roots. |
Iris - bearded, German | Iris spp. | 1 to 3 years | 4 to 6 weeks after flowers are finished blooming | Fewer blooms indicate need for rejuvenation. Cut groups of leaves back to fan shape to reduce water loss. Use a sharp knife to cut the rhizome (root) into 3-4" sections with at least on fan of leaves and roots. Discard older part of plant. |
Iris - Siberian | Iris siberica | 6 to 10 years | Spring* or late summer/early Fall** | *In spring divide before leaves are 3" to 4" tall. Dividing too late can stop bloom for an entire season. **In early fall, cut leaves back to 6" to 12" and then divide. Use sharp knife to cut rhizome. |
Jack-in-the-pulpit | Arisaema triphylla | Annually; as needed | Fall | Divide offsets when plant is dormant |
Jacob's ladder | Polemonium coeruleum | 6 to 10 years | Spring | Divide by hand (no spade or fork). |
Japanese painted fern | Athyrium niponicum | Annually; as needed | Spring or fall | Use sharp knife to cut rootstock. |
Japanese spurge | Pachysandra terminalis | Annually; as needed | Spring | |
Joe Pye weed | Eupatorium purpureum | 1 to 3 years | Spring to summer or early fall | Use knife to slice woody crown. |
Lady fern | Athyrium filix-femina | Annually; as needed | Spring or fall | Use sharp knife to cut rootstock. |
Lady's mantle | Alchemilla mollis | 6 to 10 years | Spring or early fall | Cut crown into sections with sharp spade or knife. |
Lamb's ears | Stachys byzantina | 4 to 5 years | Spring or fall | Divide by hand. |
Lenten rose | Helleborus orientalis | Rarely; every 10+ years | Spring | Divide while plants are in bloom or immediately after they finish flowering. |
Liatris, blazing star, gayfeather | Liatris spicata | 3 to 5 years | Spring | Cut into sections with sharp knife. |
Ligularia | Ligularia spp. | 6 to 10 years | Spring or fall | |
Lily | Lilium | Annually; as needed | Late summer / early fall | There are so many types of lilies, a whole book could be dedicated to how to divide each type. |
Lily of the valley | Convallaria majalis | Annually; as needed | Spring or after flowering | Division helps to keep the plant from taking over the garden bed. |
Loosestrife | Lysimachia spp. | 6 to 10 years | Spring or fall | |
Lungwort | Pulmonaria spp. | 6 to 10 years | Spring after flowering or fall | Water regularly following division |
Lupine - Russell hybrid | Lupinus 'Russell Hybrids' | Rarely; every 10+ years | Spring | Does not like to be disturbed. |
Maidenhair fern | Adiantum pedatum | Annually; as needed | Spring | |
Marsh marigold | Caltha palustris | Annually; as needed | After flowering - May or June | |
Masterwort | Astrantia spp. | 4 to 5 years | Spring or fall | Divide with spade or pitchfork. |
Meadow rue | Thalictrum spp. | 6 to 10 years | Spring | Most species are slow to recover after division. |
Milkweed | Asclepias spp. | Rarely; every 10+ years | Spring | Difficult to divide and re-establish due to a deep brittle taproot. Dig deeply. Cut crown apart with sharp knife. |
Mint | Mentha spp. | 3 to 5 years | Spring or fall | Use division to reduce aggressive spreading. Use a sharp knife or pruner to cut apart stolons (creeping stems on the soil surface with roots and shoots). |
Monkshood | Acontium napellus | Rarely; every 10+ years | Spring | Not easy to re-establish once disturbed. Due to poisonous nature of roots, use rubber gloves when dividing tuberous roots. |
Mum - garden, hardy | Dendranthema x grandiflora | Every year | Spring | Will survive longer and be most vigorous if divided and replanted every spring. Discard central core. |
Obedient plant | Physostegia virginiana | 1 to 3 years | Spring | Spreads easily in moist soil conditions. |
Ornamental grasses | Annually; as needed | Spring | Most grow well for years without division. Discard old, central portion of crown. Use sharp knife or spade to divide smaller grasses; use hatchet or ax on large grasses. | |
Ostrich fern | Matteuccia pensylvanica | Annually; as needed | Spring | Use a sharp knife or pruner to cut apart the rhizome connecting the individual plants. |
Painted daisy | Tanacetum coccineum | 1 to 3 years | Spring or late summer | |
Pasque flower | Pulsatilla vulgaris | Rarely; every 10+ years | Spring or fall | Does not like to be disturbed. Fragile roots may die if bruised. |
Peony | Paeonia sp. | Rarely; every 10+ years | Early fall, mid-August / September | Does not like to be disturbed. Dig around plant & slit roots with sharp spade. Roots are thick and brittle. Replanting too deep can diminish flowering. |
Perennial sweet pea | Lathyrus latifolius | Rarely; every 10+ years | Spring | Difficult to re-establish after division. |
Periwinkle | Vinca minor | Annually; as needed | Spring or fall | |
Phlox - creeping | Phlox subulata | 1 to 3 years | Spring or early fall | Replannt only non-woody stems. |
Phlox - tall | Phlox paniculata | 2 to 4 years | Spring or late summer | Discard central core if woody or dead. |
Pigsqueak, heart leaf Bergenia | Bergenia cordifolia | 4 to 5 years | Spring or summer | Cut rhizome with sharp knife. Transplant divisions fairly deep into soil. |
Pincushion flower | Scabiosa columbaria | 4 to 5 years | Spring | Plants can be slow to re-establish, but will do so eventually. |
Pinks | Dianthus spp. | 1 to 3 years | Spring | Dividing every few years can often extend longevity. |
Poppy - oriental | Papaver orientale | 6 to 10 years | Mid- to late summer | Seeds if allowed. Transplants can be planted in the spring. Main plant does not like to be disturbed, so can be difficult to re-establish after transplant. |
Prairie smoke | Geum triflorum | 1 to 3 years | After flowering in late summer | Young plants can be easily dug up and transplanted. |
Primrose | Primula sp. | Annually; as needed | Spring after flowering or early fall | Divide by hand. |
Red barrenwort | Epimedium x rubrum | 6 to 10 years | Spring or fall | If conditions are favorable, can be left undisturbed for years. |
Rockcress | Aubrieta deltoidea | Annually; as needed | Spring | |
Rose mallow, perennial Hibiscus | Hibiscus moscheutos | Rarely; every 10+ years | Spring or fall | Plants are slow to send up shoots in spring, so fall division might be easier. |
Russian sage | Perovskia atriplicifolia | Rarely; every 10+ years | Spring or fall | Does not like to be disturbed, so transplanting can be challenging. |
Sage | Salvia spp. | 6 to 10 years | Spring or fall | Dividee when center of plant dies. |
Sea lavender | Limonium platyphyllum | Annually; as needed | Spring or early fall | Carefully divide the long roots. |
Sedge | Carex spp. | Annually; as needed | Spring | Divide with spade or pitchfork. |
Sensitive fern | Onoclea sensibilis | Annually; as needed | Spring or fall | |
Shasta daisy | Leucanthemum x superbum | 1 to 3 years | Spring or fall | Regular division can extend their life. Discard old central portion. |
Snakeroot, bugbane | Actaea racemosa (formerly Cimicifuga racemosa) | Rarely; every 10+ years | Spring | Resents disturbance. Cut plant into sections with sharp knife or spade. Discard old, woody, central clump. |
Sneezeweed, Helen's flower | Helenium autumnale | 1 to 3 years | Spring or fall | |
Snow-in-summer | Cerastium tomentosum | 1 to 3 years | Spring or fall | Can be divided virtually anytime. |
Snow-on-the-mountain | Aegopodium podagraria 'Variegatum' | 1 to 3 years | Spring or fall | Can spread quickly and become aggressive. |
Soapwort | Saponaria ocymoides | Annually; as needed | Any time during warmer months | |
Solomon's seal | Polygonatum odoratum | 6 to 10 years | Spring or fall | Use a sharp knife to cut up knobby rootstock. |
Speedwell | Veronica spp. | 3 to 5 years | Spring or early fall | |
Spiderwort | Tradescantia x andersoniana | 3 to 5 years | Spring up until flowers bud and start to bloom | Division ensures replication of cultivars |
Spotted dead nettle | Lamium maculatum | 4 to 5 years | Spring | Can also be divided mid-summer if cut back and watered well while taking root. |
Stonecrop | Sedum spp. | 4 to 5 years | Spring | Divide by hand. |
Sundrops, evening primrose | Oenothera spp. | Rarely; every 10+ years | Spring or fall | Most species do not divide well. Oenothera fruticosa needs to be divided every 1 to 3 years. |
Sunflower | Helianthus spp. | 1 to 3 years | Spring or fall | Regular division improves performance and keeps this potentially aggressive plant under control. |
Sweet woodruff | Galium odoratum | Annually; as needed | Spring or fall | Divide by hand. |
Thrift | Armeria spp. | 4 to 5 years | Spring | |
Thyme | Thymus spp. | 4 to 5 years | Spring | |
Tickseed, Coreopsis | Coreopsis | 1 to 3 years | Spring or early fall | Cut crown apart with sharp knife. Coreopsis grandiflora and Coreopsis lanceolata live longer if divided every 2 to 3 years. |
Toad lily | Tricyrtis hirta | 6 to 10 years | Spring | |
Trillium | Trillium grandiflorum | Rarely; every 10+ years | Spring or late summer | Does not tolerate disturbance well. |
Turtlehead | Chelone spp. | 4 to 5 years | Spring | When young offshoots are 1" high, dig with spade to sever from parent plant. |
Violet | Viola spp. | Annually; as needed | Spring or fall | Divide by hand. |
Virginia bluebells | Mertensia virginica | 3 to 4 years | Spring | |
Wild ginger | Asarum spp. | 6 to 10 years | Spring or early fall | Use sharp knife to cut rhizome. |
Yarrow | Achillea spp. | 1 to 3 years | Spring | Separate by cutting or pulling apart. Discard central woody core. |
Yucca, Adam's needle, ivory tower | Yucca filamentosa | Rarely; every 10+ years | Spring | Resents disturbance, so divide only young plants. Established plants have deep, thick roots. |
Useful chart. Thanks!
ReplyDeleteI can only see from F on - not sure where A-E is?
ReplyDelete