How to multiply plants by division

SINGAPORE – In past columns, we covered basic methods of plant propagation. This month, we will focus on a simple method of multiplying plants: by dividing them.

This involves separating a larger, clumping plant into two or more plantlets. Plants that can be divided have certain characteristics that enable them to survive when split into smaller sections.

The first type of divisible plant is one that grows in tight clumps. New growth – in the form of a crown of leaves – appears from the base of the mother plant. The increased growth gradually spreads outward with time, resulting in a mass of crowns in a clump. 

Plants with such a growth habit include sympodial orchids like dendrobiums and oncidiums; foliage plants such as the peace lily (Spathiphyllum) and spider plant (Chlorophytum comosum); and the edible Chinese chives (Allium tuberosum) and lemongrass (Cymbopogon citratus).

The second type of plants that can be divided produces underground storage organs such as bulbs, corms and rhizomes. These typically produce smaller bulbs or corms around the mother plant that can be dug up, separated and replanted.

Some plants that grow by producing more bulbs are the African hosta (Drimiopsis maculata) and spider lily (Hymenocallis speciosa). The edible yam (Colocasia esculenta) and false shamrock (Oxalis triangularis) have underground corms.

Plants that spread by rhizomes, which are underground stems, can be divided by cutting and replanting sections of the rhizomes with roots attached. This can be done with many plants from the ginger order, such as heliconia and torch ginger (Etlingera elatior). 

Division may not be a viable propagation method for all plants. Do not try this with plants that have a single trunk or taproot, and lack a clump-like growth habit with multiple crowns.

How to divide a plant

Step 1: Water the plant prior to division. Avoid dividing a wilting plant.

Remove the plant carefully by digging around the plant and lifting it out. Use a spade to do this if your plant is growing in the ground. For a potted plant, turn it upside down and knock the container’s sides and base so the root ball can be easily extracted. Try to keep the root ball intact.

Step 2: Separate the clumps using your hands, a knife or spade, depending on the size of the plant and toughness of the clump. Ensure each section has healthy roots and at least one growing shoot. Some plants fare poorly when split into individual crowns.

Step 3: Prune damaged or diseased parts. You may need to cut large leaves in half for some plants to reduce loss of water through transpiration.

Step 4: Replant divisions in a growing mix at the same depth as before. Do not bury them too deeply and use a stake for support if necessary. Do not let roots dry out by leaving plantlets in the open without planting them.

Keep divided plants in a semi-shaded spot and ensure they are moist but not soggy. Once roots have been produced and some new growth has been observed, move the plantlets gradually to higher light levels before settling them in their final location.