Cymbidium Orchids Culture Note

Cymbidium Orchids are easily grown under a wide range of conditions anywhere in New Zealand, but if they are to produce vigorous growth and large healthy bulbs with resultant wealth of beautiful blooms, a little attention is necessary.


COMPOSTS: Cymbidiums must be grown in a free draining material that will retain moisture and not rot down quickly. An excellent Cymbidium mix on the market is PRIME ORCHID MIX. This is a blend of fine and coarse Pinus Radiata bark, enriched with quick and slow release nitrogen, potash, lime, trace elements and iron chelates. The Ingredients are mixed with water in a mixer until they are absorbed into the bark.


This result in a balanced, free-flowing potting mix, all adjusted to the correct pH. As pine bark is acid and not suitable for Cymbidiums. The pH (acidity) is adjusted to a suitable level by the addition of calcium and magnesium carbonate. It is far better and easier to use a balanced blend of ingredients like Prime Orchid Mix than make one’s own, as ones ideas change from year to year as to what constitutes a good mix.


FERTILISER: Cymbidiums need feeding 12 months of the year. In the spring and early summer they need high nitrogen feed to give fast growth, then during summer and winter they need a lower nitrogen level with higher potash to assist the bulbs to ripen and make flower spikes.


This can be achieved using ORCHIDFEED FERTILISER. For spring and early summer growth, I recommend Orchidfeed 212 until end of February, and then Orchidfeed 2.1.4 until next September or until the flowers are picked off the plant. Orchidfeed is a complete fertilizer, also with chelates of iron, magnesium, manganese, copper, boron, zinc and molybdenum. Use at the rate of one level dessertspoon to 5 litres of water, I now use this fertilizer exclusively on all my orchids every watering. Young non-flowering plants can be fed 2.1.2 all year round.


Other feeds such as Phostrogen or Nitrophoska dissolved in water at the rate of one teaspoon to 4 liters of water can be used if Orchidfeed is not available in your district. Don’t use the same fertilizer every time, but alternate between different brands so the plants will get a more balanced diet.


Alternative feeds are not necessary with Orchidfeed, but as Cymbidium flower spikes
need the molecule of magnesium to initiate them, additional magnesium is necessary in
the form of Magnesium Sulphate applied monthly at the rate of one teaspoon dissolved in 4 litres of water, and then watered into the plant after watering, especially from October to April or better still, all year round. Every alternate watering gives best results. ALWAYS water the plant thoroughly first, at least two — three tills, until the water is pouring out of the drainage holes every time the pots are filled, and then apply liquid fertilizer. In the winter months apply the liquid fertilizer at half the strength used in the summer.


WATERING: This is the most important aspect of growing Cymbidiums as more plants are lost by over-watering than by any other factor. A plant cannot be over-watered by giving it too much water at one watering time. It is over-watered by watering too often. In fact most orchid growers do not give their plants enough water at watering time, and this is the reason why so many plants have all those leafless bulbs in the center of the plant. It is because the roots have dried out through lack of water and then the leaves fall off.


As a guide, plants growing in Prime Orchid Mix in 10 litre plastic buckets would be watered twice a week in summer and once a week in winter. Cymbidium mats to be healthy and vigorous must have air and this can only be achieved if there is a lull between waterings which will allow the compost to dry out to a moist state. Smaller plants in, say 7 or 12 cm pots would be watered up to twice a week in summer and once in 10— 14 days in winter. Never water the plants when the compost on top of the pot is still damp
— wait till it looks quite dry but damp. Always water thoroughly till the water is pouring out the drainage holes. This may require dunking the pot in a tub or tilling it up two or three times with water so it is thoroughly soaked.


If only a few plants are to be watered, it is almost impossible to soak the plant with one quick watering as the surface tension of the dry bark actually repels water until it is damp. Therefore it is far better to water lightly on top of the pots, leave them for a while end then come back and give a thorough soaking some time later; by then the surface of the bark will be quite damp and the water will soak in.


LIGHT: A general rule for flowering size plants is to give sufficient light so that the foliage is a yellowish light green rather than deep green. Deep lush green leaves are caused by too much shade, which will give beautiful foliage, but the result will be few or no flowers. The ideal amount of shade is best achieved by growing the plants in a shadehouse covered with fiberglass... Durolite F is the best, but Corolite or Novaroof are also quite good. The house can be constructed with a pipe or wooden frame with the fiberglass screwed over it. The sides of the shade-house should be covered up to a height of around 46 – 60 cm to keep out draughts, with shade-cloth sides for ventilation. In colder areas Polythene could be stapled on the sides for the winter, but louvers or vents would also be necessary, as Cymbidiums do not like stuffy conditions even when it is cold.


Plants should also be spaced with at least a pot between the plants. They must not be jammed up along side each other as this will also make them too shady and stop them from flowering. They should be sorted out so all the different sized pots are grouped together.


PESTS: Cymbidiums have very few pests and diseases. Therefore, for your plants a combination spray such as Maverik would be suitable, sprayed once a month.


POTTING: Young Cymbidiums in 7, 10 and 12 cm pots need to be potted into larger sizes every 6 – 12 months, then every 2 – 3 years when mature, until they reach a size where the container is too large to handle. This will take 10 – 12 years. Do not divide Cymbidiums until they are huge plants and too heavy to handle. Why break up a plant when it has filled the pot...Just put it into a bigger tub or barrel. The reason for growing plants is to get flowers, and the bigger the plant, the more spikes per bulb and more flowers on a spike. This only happens on large plants. If a plant is broken up, it has to establish itself again, and also produces fewer flowers.


When they are too large to carry, they can be divided in the spring into clumps of at least  3 – 4 green bulbs, to ensure plants are large enough to size to establish quickly again in a new compost and flower the Following season. After dividing the plant, the root system should fill the pot tightly; the polling mix is shaken and lightly worked in around the roots until the pot is full and the plant quite firm. The size of the pot the division goes into is determined by the amount of roots on it, never by the size or number of bulbs and leaves. Prime Orchid Mix should never be used directly from the bag, as it is far too dry. For the best results it has to be damped down with water and turned over several times. Never use the mix while it is too wet and sticky, as it won’t flow in and around the roots while potting. A potting stick to ram the compost in around the roots ensures good results.


After a plant has been divided, it should be kept in a warm slightly shaded position. The compost should not be watered, but only dampened down on top of the pot for 3 – 4 weeks as this will give the roots a chance to heal and recover from the shock of being divided. It will sulk and possibly take years to get established and flower again. More divisions are lost through watering too often than any other cause. Any cuts where the plant is divided or back bulbs taken off should be sealed to stop rot getting in, with Sulphur or tar. After dividing, the green bulbs will shrivel a bit but this is quite normal.


When dividing, old defoliated back bulbs can be removed and potted up in a 10 cm pot, placed in a warm position, and In due time will produce a shoot which will grow, and with repotting into a larger pot each year, should reach a size large enough to flower in 2 – years, If one has bottom heat, such as a propagator, up to 16 months can be saved to flowering time as the propagation will grow much faster.


Small plants in 7, 10, 12 or 15 cm pots can be potted on in the spring into larger sized pots as long as they have a good root system. If not, they can go back into the same sized pot, or even smaller, to encourage roots.


FLOWERING: In autumn when the flower spike start showing, plants can be brought into the glasshouse, porch, verandah or carport, but not inside the home. Many spikes are lost by bringing them into the house too soon, as night temperatures above l2°C (55°F) will cause the buds to yellow and fall off. However, once the buds open it is quite safe to bring the plants inside the home. It they are to be flowered in a glasshouse or out in the open, a little shade is necessary to stop the sun fading the colour of the blooms. For clearer and stronger colour in flowers, light shading plays an important part, although they will need more shading once they are fully open


The flowers should not be left on the plant too long, say 3 weeks after the last flower opens. If left, particularly on young plants inside the home, the plant, because of lack of light, will slow down and become soft and sappy with a resulting lack of new growths on which to produce next season’s flowers, however, on larger specimen plants flowers can be left on until they die with little loss of blooms next season.


After the flower stem has been cut and put in a vase, the plant can be moved outside, if danger of frost is over, to the position where it will grow during the summer; otherwise it should stay in a glasshouse, or outside under cover, until the weather warms up.



GENERAL: Cymbidiums grow well out of doors in mild areas all year round, but must be protected from frosts. Best results are obtained if plants are brought under cover to protect the flowers. If no cover is available, a piece of polythene tacked to a frame and fixed over the plants to keep the worst of the rain off is sufficient. Plants should never be grown inside the home as conditions are too stuffy and dry, but should be outside in broken sunlight, in an open, airy position that gives maximum sun all day. If growing plants outside under a tree, ensure the plant Is well off the ground, by standing it on a brick or piece of concrete. This will discourage slugs, worms, etc, from finding their way through the drainage holes. Plants should not be placed under a tree near the trunk, but kept out under the outer perimeter of the branches where they will get direct but broken sunlight all day and not just for a few hours.



IMPORTANT: Cymbidiums need cool nights in summer to initiate flower spikes, with a drop of 11°C between day and night temperatures. This cannot be achieved in a closed-in porch or glasshouse with little ventilation.