Time to split?

Some perennials need to be divided every three to five years. Which ones need it and when? They’ll tell you.

Some perennials will look kind of dead in the centre if you look at them from above. Others will just start blooming less than they did in previous years.

You can divide any time after the plant has bloomed provided there is enough growing season left for the plant to recover from the process. If you’re nervous, go with this rule: anything that blooms in April, May or June, divide right after blooming. Anything that blooms in July, August or September, divide in early spring.

In general, don’t divide on a super hot and muggy day. And water the plant you’re going to divide a day before, so it’s well hydrated.

Before you dig up a plant for dividing, it’s best to prepare the site it’s moving to. Some plants don’t do well for long if they’re dug up. You can put wet cloths or paper towels around the roots if they won’t be replanted immediately.

In addition to improving plant health by dividing, you can increase the size of your gardens or share plants with friends and neighbours.

Step 1: Dig up the plant. Loosen the soil all the way around the dripline of the plant with a spade or fork and gently try lifting. If it doesn’t lift, loosen the soil a little deeper.

Step 2: Cut the mother plant at the roots into (generally) four pieces. Some you can divide with your hands, some you need spades, knives or even saws to divide.

Step 3: Plant in the new place and water.

That’s it! Your new divisions should grow much more happily than the original plant.

Blanket flower.

Don’t divide these

Candytuft (Iberis sempervirens)

Carnation (Dianthus caryophyllus)

Delphinium (Delphinium × elatum)

Garden sage (Salvia officinalis)

Lavenders (Lavandula)

Rose campion (Lychnis coronaria)

Russian sage (Perovskia atriplicifolia)

Sea hollies (Eryngium)

Silvermound (Artemisia schmidtiana)

Trillium (Trillium grandiflorum)

Hand divide

Blanket flowers (Gaillardia)

Bleeding hearts (Dicentra)

Bugleweed (Ajuga reptans)

Columbines (Aquilegia)

Coral bells (Heuchera)

Cranesbills (Geranium)

Creeping Jenny (Lysimachia nummularia)

Deadnettle (Lamium maculatum)

Epimediums (Epimedium)

Foam flower (Tiarella cordifolia)

Forget-me-not (Myosotis sylvatica) H

ellebores (Helleborus)

Jacob’s ladder (Polemonium caeruleum)

Lady’s mantle (Alchemilla mollis)

Lamb’s ears (Stachys byzantina)

Moss pink (Phlox subulata)

Primroses (Primula)

Pulmonarias (Pulmonaria)

Pussytoes (Antennaria dioica)

Sea thrift (Armeria maritima)

Speedwell (Veronica spicata)

Spurge (Euphorbia myrsinites)

Stonecrop (Sedum spectabile)

Sweet woodruff (Galium odoratum)

Wormwood (Artemisia ludoviciana)

Yarrow (Achillea millefolium)

Use a spade or fork

Anemone (Anemone × hybrida)

Asters (Aster)

Bee balm (Monarda didyma)

Bellflowers (Campanula)

Big bluestem grass (Andropogon gerardii)

Black-eyed Susans (Rudbeckia)

Blood grass (Imperata cylindrica)

Cardinal flower (Lobelia cardinalis)

Catmint (Nepeta × faassenii)

Coneflower (Echinacea purpurea)

Daisy (Leucanthemum × superbum)

Daylilies (Hemerocallis)

Forest grass (Hakenochloa macra)

Fountain grass (Pennisetum alopecuroides)

Garden phlox (Phlox paniculata)

Gaura (Gaura lindheimeri)

Goldenrods (Solidago)

Gunnera (Gunnera manicata)

Hostas (Hosta)

Japanese painted fern (Athyrium niponicum)

Ligularia (Ligularia dentata)

Masterwort (Astrantia major)

Monkshood (Aconitum napellus)

Penstemons (Penstemon)

Perennial sage (Salvia × superba)

Pinks (Dianthus plumarius)

Poppies (Papaver)

Red hot pokers (Knifophia)

Sedge (Carex morrowii)

Siberian iris (Iris sibirica)

Silver grasses (Miscanthus)

Snakeroot (Cimicifuga racemosa)

Switch grass (Panicum virgatum)

Tickseed (Coreopsis verticillata)

Turtlehead (Chelone glabra)

Yarrow (Achillea filipendulina)

Saw the crown into quarters

Astilbes (Astilbe)

Bear’s breeches (Acanthus spinosus)

Bluestar (Amsonia)

Doll’s eyes (Actaea pachypoda)

Foxtail lilies (Eremurus)

Gayfeather (Liatris spicata)

Goatsbeard (Aruncus dioicus)

Joe Pye weed (Eupatorium maculatum)

Lilyturf (Liriope spicata)

Male fern (Dryopteris filix-mas)

Meadowsweets (Filipendula)

Peonies (Paeonia)

Solomon’s seal (Polygonatum odoratum)

Cut the rhizomes or tubers with a knife

Arum (Arum italicum)

Bergenia (Bergenia cordifolia)

Corydalis (Corydalis lutea)

Irises (Iris)

Lady fern (Athyrium filix-femina)

Lily-of-the-valley (Convallaria majalis)

Rhubarb (Rheum palmatum)

Rodgersia (Rodgersia pinnata)

Spurge (Euphorbia griffithii)

Wild ginger (Asarum europaeum)