To dig up and split plants using varying degrees of physical force,
thereby increasing your plant stock and
improving the health, vitality, and blooming capacity of the plants.
WHICH PLANTS NEED IT?
You can tell plants need dividing if: the center crown dies; they raise up out of the ground as a result of crown density; plants stop or drastically slow down blooming.
Some plants MUST have regular dividing (e.g.: mums, German Iris)
Some plants don’t need dividing and stay put (e.g.: peonies, Dictamnus)
Get to know the individual requirements of your plants!
If plants bloom in the spring or summer, divide in the fall.
If plants bloom in the fall, divide in the spring (e.g.: divide mums and ornamental grasses in spring) Early fall bloomers can also be split in late fall after blooming.
Divide plants when weather is cool and damp: in southern CT, April to late May or mid September to late October.
Dig entire plant out of the ground, place on a tarp; never try to take a small piece of a plant out of the ground and leave the rest in—this is a great way to demolish a plant!
Once out of the ground, cut back bulk of foliage by at least 1/3, but no more than 2/3.
Look for natural separations in the crown—divide along these lines using various degrees of force (e.g.: trowel, sharp knife, spade, two pitchforks back-to-back, saw, ax, dynamite—just kidding!)
Prepare soil for replanting by digging deeply, then backfill, amending with rock phosphate, greensand, and compost to encourage strong root growth. Plant at same depth as before.
Mulch thickly around crowns to keep soil warm and encourage rooting. Water well and deeply for first two weeks.
Apply winter mulch of salt hay or evergreen boughs in late fall, after soil has frozen to keep it frozen and prevent heaving of crowns; apply Wiltpruf (an anti-dessicant) to the canes of roses.
In an effort to provide horticultural information, these educational documents are written by Nancy DuBrule-Clemente and are the property of Natureworks Horticultural Services, LLC. You are granted permission to print/photocopy this educational information free of charge as long as you clearly show that these are Natureworks documents.