Archive Article: February, 2010
The genus Cymbidium mainly comes from the mid-range altitude of central Asia. Over the years, cymbidiums have been propagated and developed by dedicated growers to achieve the spectacular range of size and color that can be seen today and they are the genera that gardeners traditionally think of when orchids are mentioned. While cultivation in the home garden is generally easy, there are a few key considerations that can greatly improve the amateur grower’s success. This article is intended to provide an outline of some of the topics that should be considered.
Growing Cymbidiums
Most cymbidiums are purchased as flowering plants which have already formed a clump of what are called pseudo bulbs. These pseudo bulbs are dependent on each other for the sharing of nutrients and moisture. The older pseudo bulbs, which are generally leafless, are referred to as ‘back bulbs’ and are the plant’s reserve stores of moisture. It is worth remembering that if these are removed for either propagation or division, extra care must be paid to maintain the plants moisture levels.
Cymbidiums are stage developmental growers. This means the plant has different requirements as it moves through a seasonal growing cycle. The new growth or lead has a high water requirement, and usually emerges as the flowers are finishing. By this stage, the plant is already developing the next season’s flowers so a low nitrogen fertilizer should be used to promote flower initiation. As the lead starts to become a bulb, usually five or six months later, high nitrogen fertilizer is used to produce a large bulb and boost the plant pre-flowering.
The Growing Environment
Cymbidiums will grow very well for the average enthusiast on a patio or in the garden, although care should be taken to give plants protection from extremes such as frost or temperatures over 104°F. They are very keen on ventilation, so choose an open, airy position. Many gardeners have had success growing cymbidiums in the ground by placing them in a very free draining garden bed. The position of your cymbidium is also crucial if the plant is to be grown in the ground, as high light is required to give the best flowering results. Foliage color is a good indicator of light intensity, with dark green often meaning too little light, and pale green to white meaning the foliage is about to burn. From the point of view that we grow cymbidium for flowers, I would rather see burnt leaves and lots of spikes than broad dark green leaves and no flowers.
A stem of cymbidium Khan Flame ‘Barrita’. Bright colors are in high demand as cut flowers.
Feeding and Watering
Although Cymbidiums have evolved to overcome prolonged dry spells, they are more than happy to avoid them. Access to frequent watering without water-logging will allow plants to take as required. It is unnecessary to dry plants between watering and plants in pots will have higher water requirements, particularly in the warmer months. Fertilizing plants is the icing on the cake, the final part of the process. Management of watering is much more important, though it is fertilizing that is at the forefront of most people’s minds. Cymbidiums are capable of growing in the garden with little attention in this area, though a regular application of a balanced fertilizer will give an increase in growth. Experienced growers will reduce the ratio of nitrogen to other elements in the fertilizer as the plant is initiating flower spikes. This is often done by using flower booster varieties of fertilizer.
Media Selection for Potting
As cymbidium growing is a long term project, the growing media selected must have long lasting properties. When growing in pots, having to re-pot your plant repeatedly due to water logging caused by degrading mixes can have a significant negative impact on your plants. Because of this, inert, long lasting materials are the best choice. A horticultural rockwool and perlite mix is one excellent media choice and because inert media does not contain any nutrients, a soluble fertilizer is recommended.
Re-potting
Developing a healthy clump of pseudo bulbs is crucial in getting the best from your cymbidium, and re-potting is a major part of this. Using methods that reduce the incidence of division are the key, as once a plant is divided it will set back the growth of the plant and severely impact the potential of the plant to produce flowers in the following season.
When plants are young, use slip potting. Simply remove the outgrown pot and select a pot approximately two inches larger and the fill the gap with new media. Not disturbing the roots will keep the plant growing. This should be done as soon after flowering as practical. As plants mature and develop a clump it may be necessary to remove some of the leaves from the older bulbs. This process is known as ‘stripping’ and allows the new growths access to the light, encouraging them to grow back into the centre of the plant and creating ‘stacking’ of the bulbs. Using stacking greatly reduces the need for division.
Pest and Disease Management
Cymbidiums are subject to a number of pests and diseases. It is important to be able to identify these problems to protect flowers and foliage. Swift treatment with an appropriate, commercially available product is advisable.
Pests of the Plant Foliage
Cymbidium Scale is often seen in older plants. It shows as a yellow discoloration on the leaf. As the pest increases in numbers they may be seen around the back bulbs.
Two spotted mite is a very small pest often known as red spider. These pests are active usually during the warmer months. They cause a silvering of the underside of the leaf. Severe attacks will also show up on the flowers and this will cause a distortion of the bloom.
Pests of the Flowers
Thrips are prevalent on the warm spring winds and will be attracted to pale bright colored flowers. This pest will leave small clear spots on the flower.
Snails and slugs are lurking at the base of the plant until the flower you have been waiting on for a year is about to open. They will devour a flower over night. Signs are the slimy silvery trail left by the pest.
Aphids will appear in large numbers on the underside of the flower bud just prior to opening. Their attack will leave the flower distorted.
Diseases
Fungal diseases often occur during the autumn and spring, and may affect the foliage. This will be seen first as small black areas on the leaf. In the worst case, plants will blacken and die.
Botrytis may affect the flowers if they are wet for prolonged periods. This will show up as fine black spots which will cover the flower. Usually this will be a problem in pale colors, although all colors may be affected.
By following a few easy steps and being vigilant of your plant’s health, you should experience great satisfaction with growing your cymbidium and enjoy many years of beautiful flowers. Good luck and happy growing!
