Dividing Perennials

Why Divide?

• It is an easy, thrifty way of making more plants.
• Some perennials decline, overcrowd and exhaust the soil. Dividing rejuvenates.
• Dividing and replanting keeps rapidly spreading perennials under control.

Why Not Divide?

• Some perennials such as false indigos, baby`s breath, sea lavender, perennial flax, lupine and sweet cicely aren`t made to be divided. They have close shoots, or have deep roots that don`t recover well.
• It`s difficult to divide perennials that form a spreading mat and are woody at the base, such as most pins and evergreen candytufts. May be propagated from seeds or cuttings.
• Other perennials can be divided, such as peonies, hostas, daylilies, goatsbeard, snakeroot and butterfly weed but will also thrive for many years without division.

When to Divide?

• When plant is not flowering or getting ready to flower.
• When a plant`s new leaves are just coming out, or its old leaves are mature.
• Divide in the spring on a cloudy day when rain is predicted or early fall.
• Divide at least six weeks before the onset of winter cold or summer heat.

How to Divide:

Bulbs:
Perennials that grow from bulbs, corms, tubers, or other underground storage organs are all very easy to divide. They may not flower well for a year or two after being divided. Along with daffodils, bulbs that recover quickly and multiply fast enough to make dividing a good idea are crocuses, meadow saffrons, snowdrops, grape hyacinths, bluebells, species tulips, ornamental onions and Asiatic hybrid lilies.

• Dig around the edge of the clump as deep as possible to loosen the soil.
• Lift up the whole clump and shake off extra soil.
• Pick, pluck or snap plants apart leaving the roots and leaves attached.
• Discard any plants that are bruised, cut or damaged.
• Replant, placing bulbs individually, burying them as deep as they were before.

Tough Clumps:
Astilbes are an example of the type of perennial that forms very dense clumps of foliage and flower stalks, with equally dense clumps of roots. The crown is usually so tight and tough that you will need a sharp tool and a strong arm to split it into three or four wedge-like divisions. Tough clumps include old clumps of goatsbeard, lady`s mantle, Joe Pye weed, false sunflower, purple loosestrife, and most sages or salvias. Toughest of all are the ornamental grasses such as Japanese silver grass.

• Dig a circle around the edges at least three times as wide as the crown of the plant.
• Pry underneath with your tool and lift the whole clump up and out.
• Hose off some of the soil. Cut with a sharp tool, in equal sections, severing between the major shoots or buds cutting right through any knots.
• Replant keeping the top of the crown level with the soil.

Mats and Patches:
Perennials that spread in this way include yarrows, anemones and artemisias, asters, phloxes, bee balms, loosestrifes, sundrops, evening primroses, mountain bluets, sweet woodruffs, and various spreading ferns and grasses. Some of these plants make good ground covers, but in a flowerbed they should be divided every few years to limit their size and renew their appearance. Mats and patches have slender horizontal stems called rhizomes, located right below the surface of the soil. The rhizomes reach out in all directions, often branching as they go and overlapping each other to form tangled mats. New shoots sprout up from all parts of the mat, forming a dense patch with lots of foliage and dozens of flower stalks.

• To renew a plant that you are going to replant in the same place, choose the best part of the patch digging around it, lifting it out and setting it aside. Tear out the rest of the patch, amend the soil, and replant the division that you saved.
• To start new plants without disturbing the mother patch, use a sharp spade to cut blocks or wedges about three to six inches from around the edge of the patch. Lift them out, transplant, and refill the holes with fresh soil.
• To divide an entire patch into several new plants, cut it all into squares, lifting them one at a time or lift the patch as a whole before cutting it.
• Large divisions rarely need special care, if the divisions are small, water and watch them carefully to prevent drying out.

Clumps:
Primroses are an example where stems are very short, often completely underground and leaves are arranged in distinct rosette, tufts or fans. Each year`s rosettes form right next to the old one, and the plant soon makes a dense clump. Rosettes include primroses, bergenias, daylilies, hardy geraniums, lamb`s ears, lobelia, lungworts, violets and Japanese painted ferns.

• The best time to divide is right after blooming, every two to three years. Divide in late summer or fall as long as the leaves are still green.
• Dig all around the plant a little beyond the edge of the leaves. Lift it out of the ground and shake out the soil.
• Choose a rosette and pinch it firmly where the leaves and roots come together. Snap it off or use a shears or knife to sever the connection pulling or prying away from the clump.
• Replant the division promptly firming soil over the roots, but don`t bury the leaf bases. Water well.