PROPAGATING ORCHIDS by Rex Johnson
There are several different ways to propagate orchid plants. Some are easy and uncomplicated, whereas others may require a laboratory situation and trained staff.
DIVISION. The simplest and most common form of propagation for orchids, such as cymbidiums, is division. This procedure simply involves removing the plant from its pot, shaking it to remove most of the mix from the root system (which often also untangles much of the root ball), and cutting the rhizome linking the pseudobulbs. With large plants it is possible to make more than one division, provided at least three green bulbs are left on each division to give it a good chance to recover and flower again next season. Most orchids having a sympodial growth habit are suitable for simple division but paphiopedilums and phragmipediums should be divided only if they fall apart during re-potting. The best time to divide any orchid is when new growths and roots begin to appear.
BACK CUTTING. Orchids that have non-clustered pseudobulbs and distinct rhizomes (for example, cattleyas) can be divided by cutting the rhizome midway between two growths. It is best to leave at least three growths on either side of the cut, as this will usually force an eye on the older side of the cut to produce a new lead. After back cutting, it is common to leave both divisions in the pot undisturbed until new growths and roots are established. With mature plants more than one back cut can be made and all divisions left in the pot for later separation or to allow a specimen plant to develop. Back cuts should be made only with sterilized cutting instruments. Some growers use new scalpel blades or razor blades and discard them after one use. As soon as the cut has been made it is advisable to place a match or piece of plastic into the cut to stop the join from growing back together, and then dust with fungicide.
KEIKIS. Nature's way of propagating some orchids is for the plant to produce aerial growths (keikis) from nodes along the stem. After the growth is formed, it soon produces roots. Once the roots are established, the keiki can be twisted or cut off and planted separately to form a new plant, which is identical to its parent. It's best to wait up to a year before removing the keiki, as by this time a second growth is usually on the way.
STEM CUTTINGS. Soft cane dendrobiums (nobile type) can be divided as described above, but an alternative method entails removing old leafless growths (ones that did not flower or produce keikis), cutting them into pieces, and then planting them in a fine-grade bark mix. Allow the cut surfaces to dry and harden for a few hours before potting the cuttings. The nodes that normally produce blooms or keikis will then produce roots. Stem cuttings usually take three to five years to produce flowers. Thunias can be propagated in the same way.
SEEDS. All hybrids are produced from seed. Hybridists pollinate flowers, which eventually produce seedpods. When ripe these seedpods are harvested and taken to a laboratory where the seeds are germinated under sterile conditions and then grown on into seedlings in flasks.
TISSUE CULTURE. As with raising orchid seeds, propagation by tissue culture is a laboratory procedure. Tissue culture involves extracting the growing eye in the meristem tissue of an orchid's new growth and dividing it many times to form new plants, each identical to the parent plant. Seed raising and tissue culture are specialized operations not usually undertaken by the average orchid grower.