Propagating Cymbidiums by Backbulbs
Figure 1 This Cymbidium backulb, covered with dry, brown sheathing, may appear dead, but it is more than alive - and capable of producing an entire new plant
Anyone who has ever grown cymbidiums knows that these wonderful plants are probably the most robust growers of all the orchid family. One of the easiest but often misunderstood ways of propagating cymbidiums is through the growing of the dormant backbulbs. There is a natural tendency for these plants to drop their leaves and produce backbulbs, which, when separated at the time of repotting and sprouted, may be used to increase the size of one's collection quite easily. In this manner, one small plant may be grown and propagated into many within just a few years.
Figure 2 With an easy twist, the backbulb breaks free from the mother plant
Of course, the main consideration before repotting a cymbidium is the condition of the potting mixture. Broken-down mix results in a slower growing plant with a deteriorating root system, which produces more and more backbulbs. Most California growers use a mix of varying grades of fir bark. This will hold up well for four or five years before it breaks down substantially.
When it is time to repot a cymbidium, the problem of what to do with the backbulbs arises. One of the most commonly asked questions from hobbyist growers is, "Are all those brown bulbs dead?" No, they are not! Along the side of each bulb are dormant vegetative eyes capable of initiating new growth. To activate the nodes the bulb must be separated from the rest of the plant. This can be done by cutting the rhizome with a sterile knife, or by applying a twisting motion until the bulb breaks free. Leave only the bulbs that hold major clumps of green bulbs together, and label the bulbs taken from the mother plant.
Figure 3 For the small-scale cymbidium grower placing dormant backbulbs immediately into individual pots may be preferable
Care of the bulbs at this point varies from grower to grower. We strip the old leaf-sheaths off for a cleaner appearance, taking care not to scar any eyes along the sides of the bulb. We have found that the most economical way to take care of the bulbs is to label them individually and set them into flats filled with fine-grade fir bark. For smaller collections the bulbs may be put directly into small pots. Growth generally initiates within a couple of months. Before this happens, care should be taken to prevent the bulbs from being exposed to full sun. If this happens for any length of time, the bulbs will cook —just like baked potatoes — and later rot.
Depending upon the variety, roots will grow soon after growth begins on the backbulbs. When the new growth is up about 6 to 8 inches, we take the bulbs from the flats and pot them up into 6-inch pots. While in the flats, and after being potted up, Cymbidium backbulbs are not treated differently from any of our other plants. They are watered at the same frequency and fertilized at the same intervals. The loss due to rot is usually quite small.
Figure 4 On a large scale cymbidium backbulbs can be placed in flats. Several months after planting, these backbulbs have sprouted nicely
Once potted, the bulbs continue to grow vigorously and usually flower in two to three years while still growing in the original pot. Thus, a grower can have many flowering-size divisions in just a few years with very little effort. It is really surprising how successful this method can be, especially when one thinks of all the back-bulbs that have been thrown away because they were considered to be of no value!
Figure 5 Removed from the flat, the actively growing backbulb pictured is ready for its own pot
Figure 6 Potted up, this cymbidium backbulb can be expected to flower within two to three years
- Santa Barbara Orchid Estate, 1250 Orchid Drive, Santa Barbara, California 93111.