Cymbidiums are a large group of grassy-leaved plants requiring different culture depending on the group they belong to. The classic hybrids are divided into 2 groups, called standards and miniatures. The standards are large-flowered, and usually lack fragrance. The miniatures are small-flowered, and also usually lack fragrance. For our purposes, we will lump them together as "Classic Hybrids". I will talk about the specific needs of each group below, but first I will cover general topics that apply to ALL cymbidium groups.
Fertilization should only be done during the active growth periods. I recommend using fertilizers at 1/4 strength of what is on the label, and only once per 3 or 4 weeks. Some cymbidiums like the Classic Hybrids can tolerate higher concentrations, but you should monitor them closely for salt damage. This will appear as a browning off of the tips of the leaves. If this happens, immediately reduce fertilization concentration and frequency, and flush the pot thoroughly with plain water.
Watering and Humidity
Cymbidium plants have evolved water storage organs (pseudobulbs) to withstand periodic, and sometimes prolonged drying in their native habitats. The larger the pseudobulbs, the longer a period of dryness they are equipped to deal with. For this reason, it is recommended that plants in cultivation be allowed to go nearly dry between waterings. Watering once a week is usually sufficient for most plants, unless conditions are excessively hot and/or dry. Smaller plants may require watering every 4-5 days during most of the year, until they are more mature. At cooler times of the year, plants may be left a little longer between waterings. When in doubt, wait a day to water. Always water thoroughly, allowing water to drain well through the drainage holes in the bottom of the pot.
Potting Media and Repotting
Only ever repot any orchid when it is in active growth. Under dire circumstances you can repot at other times, but you must be very careful to not kill the plant until it starts active growth. There are as many different media to choose from, as there are cymbidium growers. Many people opt for mixes that are very terrestrial-like, mixes that incorporate a lot of humus or wet mulch materials. I find that these break down too quickly and can lead to root rot. Bark mixes are good for the most part, provided that there is an ingredient to retain some moisture, like coconut husk. For many of the chinese cymbidium species, rock or gravel is often used, but I find that this dry growing method does not give me the number of new growths that I would like to see. After much experimentation, I have come up with my own blend that maximizes growth and root development. I use an inert mix of sponge-rock (large perlite), charcoal, coarse perlite and granular rock-wool. This mixture never breaks down, and roots grow like crazy in it. The small amount of rock-wool holds moisture, but the abundant amount of perlite allows lots of air in to keep the roots healthy. In this mix, I simply repot when the plant outgrows its container. In organic mixes, you should repot every one to two years depending on how quickly your particular mix breaks down. Your orchid media source should be able to provide guidance here.
Classic Hybrids and large-bulbed/large-flowered species
Easy to grow, sometimes tricky to bloom. Most of these plants are large growers, with showy flowers that lack fragrance. Some large-bulbed/large-flowered species are lowianum, wilsonii, mastersii and traceyanum.
These plants need a good amount of light to grow and flower well. A good guide to whether or not a plant is getting the proper light is the colour of the leaves. They should be a medium green, rather than a dark lush green. If you grow indoors, try to summer your plants outside to give them maximum exposure to sunlight. It is VERY important to introduce them slowly to the stronger light, otherwise you will severely burn your leaves.
The best general temperature range for growth and flowering is 25 ° C during the day, and 13 ° C at night. However, these plants are very resilient and can tolerate a wider range of temperatures if the humidity and watering are adjusted. A good rule of thumb is to increase humidity and watering at higher temperatures, and reduce both of them at lower temperatures.
Stop all fertilization at the end of August. Use only plain water to flush the pot during the month of September. As cooler weather approaches, reduce watering to almost nil, and permit the plants to cool off at night. It is important to combine cool nights, no fertilizer, dryness and bright light to prepare the plants for setting blooms. They need usually at least 6 weeks of this treatment to properly initiate spike development. If any of these factors is overlooked, you may have to wait another year to try again. Usually at the beginning of November, you can bring the plants inside for the winter. Try to place them in a cool location and water only sparingly until you see the spikes starting to show. Then gradually return to your normal schedule and enjoy the blooms !
Chinese species cymbidiums
Easy to grow and bloom. Some examples are sinense, ensifolium, kanran, goeringii, and forrestii. The warmest grower is ensifolium, sinense is intermediate, and the others are the cool end of intermediate. Most of these species are highly fragrant, and quite compact in their growth habits. If the following details appear confusing for the beginner, try treating them as you would a phalaenopsis. This is usually sufficient for good results.
These plants need a moderate amount of light to grow and flower well. A good guide to whether or not a plant is getting the proper light is the colour of the leaves. They should be a rich green, rather than a medium green. It is preferable to keep your plants indoors year-round, rather than put them out in diffused sun. The leaves are easily burnt or otherwise damaged, and they are one of the most attractive features of these plants !
The best temperature range for growth and flowering is
- Warmer growers : 27 ° C during the day, and 16 ° C at night.
- Intermediate growers : 25 ° C during the day, and 13 ° C at night.
- Cooler growers : 22 ° C during the day, and 10 ° C at night.
However, these plants are very resilient and can tolerate a wider range of temperatures if the humidity and watering are adjusted. A good rule of thumb is to increase humidity and watering at higher temperatures, and reduce both of them at lower temperatures. Depending on your particular plant, proper bud development and opening can be jeopardized by having night temperatures too warm or too cool.
Warmer growers like to be kept wetter than intermediate to cooler growers.
Stop all fertilization at the end of August. Use only plain water to flush the pot during the month of September. As cooler weather approaches, reduce watering slightly, and permit the plants to be a bit cooler at night. The warmer growers are less particular with this, the intermediate and cooler growers will likely produce spikes anyway, but they may not open properly. When the flowers open, return to your normal schedule and enjoy the blooms!
Notes on Special Varieties
Variegated forms of these species require more attention to the proper growing conditions to maintain proper variegation. Forms with unusual flower shapes (known as "Magical Flowers") also have this requirement. Note that under poor culture, these types will lose their variegation or bloom with normal flowers instead of the unusual shapes. If these plants are returned to proper culture, they may, or may not revert to their earlier more desirable types. The "Da Mo" varieties of sinense are special dwarf forms introduced to China with the Zen Buddhist Monk called Da Mo. Improper fertilization will cause these to revert to normal forms of sinense. When dividing your special varieties, you must take divisions of NO LESS THAN 2 pseudobulbs, as single growths will almost ALWAYS revert to the wild form of sinense.
Hybrids between Classic types and chinese species
Easy to grow, and very easy to bloom. Some good examples are
- Peter Pan (ensifolium x Miretta)
- Maureen Carter (sinense x Sleeping Beauty)
- Golden Elf (ensifolium x Enid Haupt)
These plants are much more manageable in size than the "Classic Hybrids", and are much more free-blooming. They will often come into spike several times per year, without much prompting. They also often have a delightful, light fragrance.
Their flower size is reduced, but is still much larger than the species. The plants are also more tolerant of cooler temps and higher light than their species parent, but this is certainly not a necessity for their proper culture. Their foliage also tends to retain the attractive characteristics of the species parent.
For their culture, follow the guidelines of the species parent for good results.
Large-bulbed/small-flowered species cymbidiums
Easy to grow, sometimes tricky to bloom well. Some examples are madidum, and chloranthum. Treat these the same as warmer growing chinese cymbidiums, but with a bit more light. These can become robust plants.
Thick, fleshy-leaved species cymbidiums
Very easy to grow and bloom. Some examples are aloiifolium, finlaysonianum, simulans, pendulum, siamense, and atropurpureum. Treat these the same as warmer growing chinese cymbidiums, but with a bit more light. These can become robust plants, and all have somewhat pendulous, long spikes of flowers.