Dividing Cymbidiums by Carles Marden Fitch

                  When cymbidiums finish flowering, large plants can be divided.
     Proper care yields healthy cymbidiums that bear plenty of colorful flowers. Once flowering ceases is an ideal time to divide overgrown specimens. Here, a three-year-old division of Cymbidium Leodogran 'Cradlemont', AM/AOS (Sweetheart x Liliana) puts forth a magnificent show.
     Cymbidiums are easy to grow but often difficult to divide. Dislodging a clump firmly established in its container may require breaking the vessel.

     Miniature hybrids often do well for five or six years before needing division and repotting. By then, a multilead clump is huge. To dislodge a specimen, turn the pot upside down on the edge of an outdoor bench and slap the pot on the top and sides. The vibration usually loosens roots adhering to the container's walls. Next, tap the upside-down pot on the bench edge to free the root mass completely. If the slaps and taps do not work, break the pot, using a sturdy rubber-handled metal-potting tool that looks like the end of a bike handle.

        Big-tool Time
     Last spring, I broke a kitchen knife attempting to divide one big clump of a standard hybrid. The root mass--more than 15 inches tall--necessitated a bigger tool. A sturdy wood saw was the solution; pruning shears would not reach far enough into the clump for efficient cutting.

     With some care, use a sharp clean saw to divide massed pseudobulbs and roots without damaging active growths. Take steps to prevent the spread of virus. Flame sterilize the saw first, and then again before separating a new division. To flame-sterilize, pass the blade through the flame of a gas stove. If many cuts will be made, it may be beneficial to invest in a portable propane torch that clips on to a replaceable fuel cylinder.

        When to Repot
     In southern New York, cymbidiums do well when divided May into July. Active small divisions or seedlings can be gently moved to larger containers anytime. However, disturbing all of the roots and dividing clumps is safest during the warmer spring and summer months.

        Trim and Clean
     After sawing a big clump into major sections, each with at least one strong new growth (lead), continue the dividing process with bare hands. Once separated into easily handled units, pull off old leafless pseudobulbs and pot separately. Pull or shake out dead roots. When a root mass is sloppy or tangled, trim with clean, sharp sterilized pruning shears.

        Dry Time
     A grower in California once advised keeping newly divided cymbidiums dry at the roots four to six weeks. Although this forced-dry season seems extreme, it does encourage vigorous new roots. Pot each division in a container; clay is recommended because its weight helps prevent the plants from tipping. The medium I use is three parts moist bark mix and one part coarse perlite. After potting, soak the mix with a solution of SuperThrive root stimulant (1 teaspoon per gallon of water). After this initial watering, protect the freshly potted cymbidiums from rain and do not water for four to six weeks. On sunny days, I provide gentle top misting but do not water the roots. This routine encourages divided clumps to send out healthy new roots.

        Year-round Care
     Most of my cymbidiums are large-growing miniature hybrids, 24 to 36 inches across. Placing plants outdoors from early June until late September keeps them healthy. During cold months, the cymbidiums live in front of a bright basement window where night temperatures of 60 F rise to 75 F during the day. Most of the winter-growing light comes from overhead 40-watt fluorescent lamps left on 12 to 14 hours, sunrise to early evening. Broad-spectrum lamps, such as Wide-spectrum Gro-Lux, let the orchids complete healthy growths begun outdoors in the summer. During the winter, I fertilize with a low-nitrogen fertilizer--such as Peters Blossom Booster 10-30-20 or MiracleGro 15-30-15--once a month. Watering every three to five days completes this care regime that yields flowering plants in spring.