Like a seasonal magic trick, one hosta becomes two and one Heurchera (coral bells) becomes three. A tight, dense patch of daylilies or liriope split into as many as six new plants.
No wand required, but dividing perennials does demand a sharp shovel, a garden fork, a trusted knife, gloves, ready water and a plan. Splitting up older, overgrown plants improves plant health and extends the gardening budget.
Early autumn, before it gets too cold, is ideal timing for dividing many traditional garden species. They’ve finished flowering and foliage has died back. Whether a plant has roots, bulbs or rhizomes, the basic steps are the same.
Tips for Dividing Perennials
- Generously water the target plant(s) the day before digging
- Dig up entire plant if possible
- Remove parts that are damaged, diseased or dead
- Cut back the top growth
- Dunk roots in water to better see what’s there
- Divide portions from the main plant
- Replant at same depth and water well
That, of course, is the short version.
Techniques vary by type of growth
Hosta, daylilies and Japanese iris can be pried or pulled apart after a quick rinse. You should see distinct crowns with shoots coming out of each. Make sure each division has a crown and at least three shoots.
Peony, Anemone, and Tuberous Begonia have crowns that grow from tuberous-rooted stems. Once the root is unearthed, divide tubers into groups of two or three. Dahlias are in this group too, and their tubers should be stored in damp peat moss or vermiculite at 40 degrees for replanting in the spring in most areas.
Gladiolus, crocus and freesia technically grow from corms, a stem base that is more solid than a bulb. Small cormels grow above the old one and can be removed for replanting. Depending on the climate, replant hardy varieties and store tender cormels in a cool, dry place over the winter.
Daffodil, hyacinth, narcissus and allium produce “bulblets” at the base of the bulb. Separate them from the parent bulb and replant. The small ones may take a year or two to flower but the larger ones should bloom the first year.
Bearded Iris is a classic rhizome plant, divided by breaking the large, fleshy growths into pieces. Make sure each piece has roots growing out the bottom and at least one set of fanned leaves on top. Trim the fans to 3 inches, creating an arc shape with the tops.
When to Divide Perennials
Perennials that bloom less vigorously or develop “dead zones” in the center are ripe for division. Garden experts recommend different cycles for different plants.
Divide these perennials every three or four years: astilbe, bee balm (monarda), daylily, hosta, phlox, purple coneflower.
Divide these plants every other year or every third year: aster, blanket flower, coreopsis, yarrow and lamb’s ears.
Before digging, know where the divisions will be planted or establish a separate bed for new plants to give them a healthy start. If storing bulbs, corms or tubers, prep the storage material and containers.
Dense, compacted root systems will survive cutting with a knife or slicing with a spade. Use the free, “new” perennials to fill garden gaps and start another planting area that echos the existing bed from the outset.
Swap divisions with gardening friends, and wait for the magic next spring.