Question: My cymbidium orchid has just finished blooming and it looks too big for its pot. How do I repot it?
V.C., Laguna Beach
Answer: An overcrowded container is one of two good reasons to repot. The other reason is when the planting medium has broken down or turned mushy. Fir bark, for instance, turns dark brown and grainy when it has broken down.
If neither of these conditions exist, then you should leave cymbidiums alone.
A cymbidium is dormant while it is in bloom. After it blooms, new root growth begins and the plant grows until it sets the next year's flower spikes. The time to repot is at the beginning of the growth period.
First, have a look at the anatomy of your cymbidium. Since it is too crowded, the spent flower spike is pressing up against the side of the pot. Next to it, or behind it, is the most recently matured green pseudobulb from which the youngest leaves emerge. There may be several other older green pseudobulbs with leaves and then some brown leafless pseudobulbs, called backbulbs.
If your cymbidium produced more than one spike this spring, the sequence of flower spike, green pseudobulb, backbulb will be repeated from another spot on the edge of the pot, with the brown backbulbs in the center of the pot. The current year's growth will begin with a new lead, which will emerge from the base of last year's pseudobulbs.
New leads have probably already formed on early flowering cymbidiums; leads on June-flowering cymbidiums should be just beginning. Since a new lead resembles a flower spike in the early stage, look for a bulge at the top of the new growth. If there is one, it's probably a flower spike. If it's thicker at the base, with a more pointed top, it's a new lead. The lead indicates the direction of new growth and determines the placement of the plant in its new pot.
If the cymbidium had multiple flower spikes, it will probably produce multiple new leads. It can be divided into several plants if you want more. Or the entire clump can be replanted in a larger pot.
Cymbidiums require a well-draining medium that also holds moisture and nutrients. Many potting mediums can be used for cymbidiums, such as packaged cymbidium mix, fir bark mixed with peat moss and perlite, straight osmunda, tree-fern fiber and a mix of loam, dried oak leaves and redwood fiber.
They can even be planted in the ground, if the necessary conditions are met.
Select a pot that allows space for at least two years' worth of growth. If you are dividing the cymbidiums, you may be able to use the original pot for one of the new plants.
Once you have the medium and the new pots, remove the plant from its pot, which may be a real challenge for a large, crowded cymbidium that has filled its pot with roots as thick as earthworms. It may even be necessary to break the pot with a hammer or ax to remove the plant from the container.
When the plant is out of the pot, remove the old medium by gently shaking the roots and combing your fingers through them. You can also soak or hose the medium off. Try not to damage the healthy roots, which are white, plump and firm. If new root growth has started, they will have light green tips. Rotted roots are dark, mushy, or have collapsed sides, and they should be cut off.
If you are dividing the plant, split the original clump so that each division has at least three green pseudobulbs along with a few backbulbs. Dried out, leafless backbulbs can be removed, if doing so doesn't damage the rest of the plant.
Hold the plant in the center of its new pot, making sure that there is room for the new leads and flower spikes to develop. Allow at least 2 inches from the leads to the edge of the pot.
Begin adding new medium evenly around the plant as you hold it in the correct position. Pack the medium gently but firmly around the roots, keeping the roots spread out. Continue adding and packing the medium until it reaches the level of the old medium.
Water the newly planted cymbidiums, but don't feed for a few weeks. Label new cymbidiums and include the repotting date.
An insecurely planted cymbidium won't have robust root growth and will take longer to reestablish itself. It should not jiggle about in its pot. You can tell if the medium is adequately firm by trying to lift the plant by its leaves. If it starts to break free of the medium, pack the medium more firmly. A correctly planted cymbidium can be picked up by its leaves, pot and all.
Cymbidiums are susceptible to a number of diseases, so sterilize all cutting and potting instruments before using them on a new plant.
Have a problem in your yard? University of California Cooperative Extension (UCCE) Master Gardeners are here to help. These trained and certified horticultural volunteers are dedicated to extending research-based, scientifically accurate information to the public about home horticulture and pest management. They are involved with a variety of outreach programs, including the UCCE Master Garden hotline, which provides answers to specific questions. You can reach the hotline at (714) 708-1646 or send your e-mail to firstname.lastname@example.org. Calls and e-mail are picked up daily and are generally returned within two to three days.
* A repotting class for cymbidium orchids will be offered today, from 10 a.m.-1 p.m at the UCI Arboretum, which is south of the corner of Campus Drive and Jamboree Road on the UCI North Campus. (949) 824-5833.