Gardening 101 Plant Guide – Splitting and Dividing Plants

These perennials prefer not to be disturbed or divided:  Alyssum  Aquilegia (columbine)  Asclepias  Baptisia  Clerodendrons (bleeding hearts)  Carnations, Euphorbias, Geraniums, Gypsophila (baby’s breath)  Hellebores don’t like to be lifted/split and moved once they are more than 3 years old. Look for small seedling plants around their bases and rather dig these up and transplant them. If you do divide them use a sharp spade or knife to cut through their woody stems and fleshy roots. Try to divide the clumps into sections with 3 to 5 healthy shoots  Iberus sempervirnes (candytuft)  Japanese anemones  Lavender  Oriental poppies  Platycodons (balloon flower)  Rosemary  Santolina (cotton lavender)

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Gardening 101 Plant Guide – Splitting and Dividing Plants

These perennials sulk for a little while after being divided:

 Clivia’s don’t like root disturbance especially when young and they like their roots to be crowded for best flowering. Divide only every 3 or more years. Like some other perennials they will skip a flowering season after being divided.  The same preference for root crowding applies to Crocosmia’s and Dierama’s, as well. Dierama’s will take time to flower after division they will sulk.  All except Crocosmia ‘Lucifer’ which has stolon’s can be divided (if you decide to divide the other Crocosmias and Dierama’s they will need to be divided very carefully and gently. In spring dig down to 30cm in order to get as much of the “chain-like” corms as possible. Separate them with “chains” intact, removed shrivelled or diseased corms and trim old leaves.  Strelitzia juncea Division is best done in autumn or winter. The fleshy roots are difficult to dig up and take time. Dividing into big clumps (60 cm plus in diameter) ensures that plants will recover quicker. It will take about two to three years before they are back to their flowering peak.  Paeonia (Garden Peony) and Paeonia lactiflora (Chinese Peony) only divide if you need to increase plants, when you divide these plants you may wait up to 3 years before they flower again. Divisions should have three to five years growth. Plant with buds no deeper than 2cm below soil.

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Gardening 101 Plant Guide – Splitting and Dividing Plants

Dormant in winter - Some perennials are evergreen but will be dormant in winter, like Aspidistra’s, some grasses like ophiopogons and many ferns. It is best to divide them in early spring.

Spreading Root Systems Perennials with spreading root systems have many slender matted roots that originate from many locations with no distinct pattern. The plant is often shallowly rooted and each new shoot is separated from the original crown with a partially separate root system. These plants can usually can be pulled apart by hand, or cut apart with shears or a knife. Stubborn roots can be pried apart using two garden forks back to back.

When and how to divide spreading root systems

Common Name How Often to Divide Method of Division Botanical Name Season to Divide Asters Every year or two to Spreading root division. (Aster) control spread and Replant outer growth and maintain vigour. discard the centres of older Spring plants. Astilbe Every 2 to 3 years or Spreading root division. Needs when crowded. Early division for best blooms. spring or autumn. Black-eyed Susan Every 3 to 4 years. Spreading root division. (Rudbeckia fulaida) Early spring or autumn. Bleeding Heart Rarely needs Fleshy root division. Be gentle (Dicentra) division. Early with brittle roots. spring.

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Gardening 101 Plant Guide – Splitting and Dividing Plants When and how to divide spreading root systems

Common Name How Often to Divide Method of Division Botanical Name Season to Divide Chrysanthemum Every year or two. Spreading root division. Spring. Coreopsis (Tickseed) Every 1 or 2 years to Spreading root division. maintain vigour Discard weak centre. Autumn or Spring Gaillardia Every 1 or 2 years to Spreading root division. maintain vigour. Early spring. Echinacea (Purple-cone Every 4 years Spreading root division. flower) Autumn or Spring Garden Phlox Every 3 to 4 years. Spreading root division. (Phlox paniculata) Early spring or autumn. (Geranium) Every 2 to 4 years. Spreading root division. Spring or autumn Lambs-ear Every 2 to 3 years. Spreading divisions. Discard (Stachys byzantina) Spring or early weak centres. autumn. Yarrow (Achillea) Every 2 or 3 years Spreading root division when centre dies out Autumn or Spring

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Gardening 101 Plant Guide – Splitting and Dividing Plants

Plants with Clumping Root Systems:

Clumping root systems are compact and these plants generally have thick, fleshy, closely intertwined roots. Use a knife to pry apart the thick, fleshy crown of roots, or 2 garden forks.

Keep at least one new bud with each new split and if you prefer larger plants, then keep at least 3 new buds. Divide these plants with a spade of garden fork. Roots offsets are small plants growing at the base of a larger one, divide the connection between any of the sections to obtain a piece with ample roots.

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Gardening 101 Plant Guide – Splitting and Dividing Plants

Common name How often to Divide Method of Division botanical name Season to Divide

Agapanthus When flowering slows down Fleshy clumping roots are large (4 to 5 years). Autumn, and brittle. Do not divide unless Spring, Summer needed to improve bloom or if more plants are needed. Aristea ecklonii Divide rooted clumps in Do not divide unless needed to (Blue Stars) Autumn improve bloom or if more plants are needed. Astible When flowering slows down Fleshy clumping roots Bulbine species Every 2-3 years. If a mature Dig up the plant cluster including bulbine flower clump’s the roots and pull the clump apart center starts to flop over, it into individual plants. is time to divide the plant. The best time to divide and replant is just before the rainy season starts. Cannas Every 3 or 4 years, or if Fleshy clumping roots (Canna) additional plants are desired. Spring. Chondropetalum When plants decline in Fleshy clumping roots. Divide root Tectorum (Cape vigour or if additional plants balls into a number of clumps with Thatching Reed) are desired a sharp spade.

Daylily Every 3 to 6 years. Ideal Fleshy clumping roots - Divide (Hemerocallis) time is after blooming. fleshy roots into segments with roots. Splits with three or more shoots will bloom sooner. Hosta Rarely need division. At Fleshy clumping roots - Divide into their best form if not divided clumps or wedges with one to too often. three eyes.

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Gardening 101 Plant Guide – Splitting and Dividing Plants Common name How often to Divide Method of Division botanical name Season to Divide

Knipholia Divide only to increase plant Fleshy clumping root system. May Red-hot-poker stock. Spring or Autumn. take 2 to 3 years to bloom. Ornamental Every 3 to 4 years. Split in Very dense fibrous root system Grasses spring - most won’t tolerate may require the use of an axe or it in autumn. saw to divide.

Sedum autumn To increase plants in Spring Clump division joy Tulbaghia violacea To increase plants or when Once the clumps that have been various species flowering diminishes. divided are planted, they should be left undisturbed for as long as possible. First flowering can generally be expected in the second or third year.

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Gardening 101 Plant Guide – Splitting and Dividing Plants

Rhizome Root Systems: These perennials have underground stems that grow horizontally slightly above ground. Surface roots run on or just below the surface of the soil. They form new Rhizomes when they contact open soil. These plants are best divided using a sharp knife to cut the rhizomes into individual fans with a few buds on each. You can cut between any of the stems, cut to have a division with its own stem and roots. Each new piece of rhizome should be at least 4 to 8cm long, with one “fan” of leaves i.e. stem. Look out for damaged or diseased sections that will need to be cut away. Re- plant the rhizome so that the top of the rhizome is just showing above the soil.

Common name How often to Divide Method of Division botanical name Season to Divide

Acanthus mollis Divide in spring or late Divided by cutting off sections of (Wild Rhubard) autumn when more plants rootstock with visible leaf buds. are needed otherwise leave them be. Aspidistra (Cast Divide thick patches in Divided into two or more plants, as iron plant) spring and replant long as each has part of the original immediately. root system and some top growth. Use pieces of the rhizome that include at least two leaves Bearded Iris Every year or two to Cut up Rhizomes and tubers with a (Iris) control spread and knife discard old damaged or maintain vigour. Spring diseased part Rhizome root division. Bergenia When the plant needs Rhizome division rejuvenation

Gardening 101 Plant Guide – Splitting and Dividing Plants Common name How often to Divide Method of Division botanical name Season to Divide

Bamboo and Adventious roots Rhizome and Stolon ferns Dietes When the plant needs Dig out a few large clumps, split the rejuvenation or more plants, then plant each individual plants are required. split about 30cm apart. Sanseviera The plants grow actively Clusters can be divided and the hyacinthoides during the summer, rhizomes planted. dividing in spring will produce the quickest results. Strelitzia Divide mature plants prior Dig up old clumps and separate the Reginae to new growth in spring underground rhizomes with a sharp and only divide plants that knife, cutting the rhizome into have been previously sections, making sure each section blooming for at least three contains a fan with roots. years and only when they have outgrown the area.

Gardening 101 Plant Guide – Splitting and Dividing Plants

Plants with Tuberous roots or Corns:

These are quite fat and “bulbous” roots, each new split has a section of the original stem and a growth bud attached. Either re-plant or store for the next

season’s planting. Dahlia carefully cut apart with a sharp knife

Chasmanthe floribunda Chasmanthe form a raised mass of corms and will continue to bloom for years without being divided, but dividing clumps every three to four years will lead to heavier flowering. Dig when dormant and cut apart sections of corms or pry out individual ones, discarding the small offsets and the flattened, dead corms that are stacked under each mature one. Replant right away. Corms may not flower in the first year after transplanting.

Crocosmia aurea The chains of corms are fragile and easily separated removing offsets from the corm in spring. The roots of the lowermost corm in a chain are contractile roots and drag the corm deeper into the ground where conditions allow.