Cymbidiums are a popular genus of orchidaceae. They are temperate climate plants known for their ease of flowering and long lasting flowers. Typically they flower once a year, close to the same time of year by influence of the species in their pedigree. The colour and form of the flowers is also heavily influenced by which Cymbidium species features in their background.
Cycle of Growth
Cymbidium orchids follow a cycle of growth, flowering and rest which is influenced by the seasons. A cymbidium plant is made up of bulbs, leaves and roots. Leaves sheath the bases of pseudobulbs (not true bulbs) that grow in circular clusters on top of the growing medium. Pseudobulbs continue to produce new leads (leaves). The base of the new leads will eventually develop into new pseudobulbs. The leaves of each bulb stay green for several years before they yellow and fall. Old bare bulbs, referred to as back bulbs, will continue to serve an anchoring function for the plant.
It is from the base of leads and bulbs that flowering spikes emerge.
Each pseudobulb is connected to another by a rhizome at its base, and bulbs can be split into divisions, and repotted to give rise to identical new plants. (Even seemingly dead back bulb placed in small pots of potting mix will strike to give rise to a new plant, although this can take several years).
A feature of cymbidiums (and all orchids) is they pack their pollen in little wax-like bundles, known as pollinia, for the visiting insects to collect. This is a unique system, which does not allow any pollen grain to be lost in the transfer of pollen from one flower to another.
The lip or central labellum of the cymbidium orchids is a modified petal, attracting to insects. It is this feature which readily attracts the human eye as well.
The majority of cymbidiums flower in autumn, winter and early spring. (Breeders have extended this timeframe with the addition of new heat tolerant summer flowering hybrids). The flowering cycle begins with spike initiation, well before flowers appear on the spikes. This usually occurs in late spring and early summer, typically November and December in the southern hemisphere. With Himalayan derived lines, a differential fall of at least ten degrees between daytime and night time temperature acts as the trigger to flowering. Commercially, plenty of light and a shock reduction in the amount of nitrogen applied relative to potassium is used to trigger spike initiation.
We expect all our mature plants to flower. We select varieties that flower their socks off. Prolific types will put up spikes even when they are only juvenile plants.
Conversely it is a fact of life that some varieties like to grow and grow and refuse to flower (we also remember the old days when in our collection were plants that neither grew nor flowered!). Why? Is it because there is a lack of sufficient light or only a short period of daylight? Are night-time temperatures too warm? What is the general condition of the plant?
Assuming there is no obvious reason for not flowering, seriously consider culling such a plant, as sad as that may be. Starting out, it is wise to develop a relationship with a grower in your area who has a proven record of cultural excellence. What applies in one country or region may not apply in another and what applies in one particular microenvironment may not apply elsewhere.
The best teacher is the plant itself and the first secret to growing cymbidiums well is observation. The following observation checklist can be used to “tune” in with your plants. We like to think of ourselves and our plants as a team, constantly communicating. Obviously plants can’t talk, so it is up to us to use our eyes and senses to observe and interpret what they are saying by their appearance and vigour and performance.
It is always wise to get a sense of the weight of your pots. We grow in plastic pots, though some prefer ceramic and terracotta pots (with drainage holes). Lift up your plant before watering and after watering. Feel the difference. This will help you judge when your plants need watering.
Healthy leaves are mid green to emerald, almost glossy and firm without any markings. Check the leaves. Your eyes should be on the lookout for suspicious necrotic markings – if in doubt, quarantine, and send a sample of tissue to your Agriculture Department to ensure it is not infected with one of the viruses that affect cymbidium orchids. Early detection will minimise the potential of spread throughout your collection.
Are they dull and tired or perky and glossy? Are they firm to touch?
If leaves are dark green, thin and long your plant may not be getting enough light, which will inhibit flowering. If leaves are short, and the older leaves are soft, turning yellow then dying (outside the normal autumn shed), it is likely the root system is not active. This could be caused through overwatering, or excess fertiliser, or the substrate medium has broken down. You will need to check the roots and repot.
If the leaves are covered in scale insects or mites you may need to consider how crowded your plants are. Crowding deprives plants of air movement, light and water-the dry protected conditions, perfect for scale and other pests to thrive.
Do the leaves have dead brown tips (die back)?
You need to know three things about this. First, this can be caused directly by under watering. Second, this may be more prominent in some genetic lines and third, it can be caused by excess salt build up in the potting mix. You need to question whether the quantity of water delivered to your plant is both sufficient, and too salty, especially for the Cym. devonianum and Cym. tracyanum genetic lines. You may need to cut back on fertilizer. Salts can concentrate and build up in the potting mix. Once the roots hit a line of high salt concentration, they stop growing with a screech. Water, rather than being taken up by the roots, is drawn out of the roots, depriving your plant of necessary hydration. The roots will shrivel and rot.
Leaves are affected by under watering. Severe under watering leads to leaf death. If you have a lot of leafless pseudobulbs, and only a few leaves around the perimeter of the pot, check you are not under watering.
Roots are essentially like straws that draw water and nutrients into your plant. The root system is an excellent indicator of your plant’s health and we cannot stress enough the importance of a healthy root system. Roots must be active for the plant to thrive.
It is a good idea from time to time to remove a plant from its pot and conduct a health check. Squeeze the pot with your hands to loosen the root ball or if tightly jammed, hold it between your feet and pull. If you have great difficulty in removing your plant it may be pot bound and most likely needs to be potted again into a slightly bigger pot. You may need to hammer the pot to get it out.
What you are looking for is for your plant to slip out of the pot with the roots and potting mix intact in one firm mass (in the mould of the pot).
Note the appearance and integrity of the roots.
Are they long, abundant and fleshy? Do you see a mass of firm pearly white or cream coloured roots with lime green or yellow growing tips? If not, don’t be discouraged, cymbidium orchids are tough, and can recover from setbacks. But be patient, it may take one or two seasons before the plant is in prize winning condition.
You can learn a lot just by the way a plant comes out of its pot. If your potting mix falls down and away, this indicates the roots are weak and haven’t anchored themselves into the potting mix – in this situation be on the lookout for roots that are brown, stubby and squelchy. This situation necessitates a major overhaul, and fresh mix.
With roots that are soggy, hollow and mushy, your plant needs rehab. Pull away the rotten roots and repot in fresh potting mix. Completely remove the old mix and select an appropriately sized pot.
Making your plant swim in a pot is a sure way to impede the ability of your plant to cycle through the wet/dry process. A waterlogged potting substrate will set up another round of rotting roots – so choose a pot only marginally bigger to accommodate the plant and aim for moist, not soggy. This is where eyes and experience come into play. When in doubt, defer to a smaller sized pot – once established, it can then be potted on to a larger pot with fresh medium.
What is important is to understand the causes of an unhealthy root system. This may come from poor quality water, over fertilizing, or even overwatering (roots are deprived of oxygen in a waterlogged potting mix). Further, if a plant doesn’t receive sufficient warmth and sunlight, water is not drawn up the roots and into the foliage through transpiration – another issue that can compromise the desired wet/dry cycle.
If the roots are short, and stubby roots this indicates deprivation of nitrogen and minerals. Check if your mix is way too porous.
Finally a point on Nursery/greenhouse hygiene.
Fungal infections are another source of rotting roots, so cleanliness is essential, picking up dead leaves and weeding regularly. Sit your pot plants off the ground on plastic or mess benches or crates. Do not use wooden pallets. Cymbidium orchids are epiphytes and will send their roots into the wood and eventually the pallets will rot and the plants are susceptible to the spread of disease.
Are the pseudobulbs wrinkled or full and smooth? If wrinkled, the plant is dehydrated. Are there more backbulbs than pseudobulbs? It should be the other way around. If this is the case your plant is starved of nutrients necessary for growth.
People grow cymbidium orchids successfully in a variety of ways. Some grow them in glass greenhouses, some plastic, some under a deciduous tree, and some on a north facing wall. We grow our plants under shadecloth in a cable shadehouse. A general rule of thumb is to build your shadehouse/growing house where your plant receives filtered sunlight from dawn to dusk, i.e. 12 hours. A location where neighbouring property and/or trees obstruct sunlight will inhibit the necessary process of photosynthesis.
Choose shadecloth suitable to your particular conditions. For example, 50% shadecloth in darker geographical regions or 70% in bright sunny environments.
Our nursery lies on the northern plains of Adelaide where temperatures reach 45 degrees Celsius during summer. Our shadehouse is covered with 70% shadecloth. Without such protection (and extra water), our plants would fry during heatwave periods.
Pots must be able to drain after watering. They can’t sit in water which could cause root rot problems. Therefore, never sit your pots on dirt or any sealed or solid surface where water cannot flow freely away. Mesh benches are ideal and provide for additional air flow.
Light and temperature
Light is essential for plant health. From the colour spectrum viewpoint, plants need red and blue light, and they reflect green. Light from the red end of the spectrum is critical for flowering while that from the blue end is used for growth.
All plants make their own food by combining carbon dioxide from the air with water. The process, called photosynthesis, can’t occur without light.
Photosynthesis involves trapping sunlight energy in the green pigment in the leaves, chlorophyll. The process creates glucose, which is converted into energy for the plant to grow. So remember, without light, plants can’t photosynthesize and if they can’t photosynthesize they can’t grow. Leaves will elongate, be dark green in colour, and the plant will be much less likely to flower.
So light is not only essential to produce the energy required for growth, it is the cornerstone to achieve magnificent flowers – the strength of the spike, the number of flowers produced, flower substance, colour and size.
Just to give you an idea of how much light cymbidiums need, professional growers provide up to 16 hours of light per day. Fly over Holland at night, and witness the illuminated glasshouses – photosynthesis turned up to the max.
From an intensity perspective, the recommendation is between 35,000 and 50,000 lux. That is a lot of bright light! Consider an office environment, typically around 850 lux.
Overcrowding of plants is a common error many beginner growers fall into which will reduce the available light. If leaves shade each other, it is like placing an umbrella over your plants – they will be deprived of not only light, but air, water and nutrition. They are also more susceptible to insect pests such as scale. We aim to keep a pots distance between each plant as they sit on our plastic pallets and benches.
The problem of hot summers
A temperature range of night temperatures of 12-18 C and day temperatures of 20–27 C is ideal for cymbidiums (click here for temperature range in F). Cymbidium orchids will survive short spells of hot weather provided they can keep transpiring. The evaporating water acts as a cooling system.
Extreme light intensity, combined with high temperature without protection of extra shade and humidity can cause permanent cellular damage. Sunburn is usually first seen at the top of the leaf arch as pale yellowing which eventually turns white and later black. In extreme cases chloroplasts, the structures containing chlorophyll within the cell will burst and the whole leaf dies.
Photosynthesis and all plant processes will slow at high temperatures and light and temperature are linked. This is why temperature for very high lux should not exceed 27 C. In other words, the cooler cymbidiums are grown, the more light they will tolerate.
At the height of an Australian summer light intensity soars and it is necessary for us to provide extra water and shadecloth over our nursery plants. We always use double shadecloth for our younger plants to help them grow without the stunting that can occur with too much light. People with greenhouses often employ retractable blinds (which can also act as insulation against the loss of heat at night). Whitewashing glass can also be used to block excessive sun but will need to be reapplied regularly.
Flowers are even more sensitive to high heat and light than plants, so if you have summer flowering plants, keep then in a cooler, moderate light environment to extend their longevity.
The problem of low light
Regions that experience bleak winters and associated heavy cloud cover need to ensure plants have every opportunity to photosynthesize. Spacing in this context is critical, the distance between each plant maximised to avoid any cross shading.
Those of you in cold climates may need extra lighting and a source of heat within a greenhouse or polytunnel. Many a collection has been decimated by a sudden overnight drop in temperature to below zero degrees Celsius. If your night-time temperatures are too low, and you cannot afford heating, you can block chilling winds with plastic or glass barriers and take measures to avoid the damage from frosts by watering. Even in our warm climate we have witnessed the irreversible cellular damage of frost. If temperatures are predicted to drop below one degree we will use water to “warm” the plants on frosty mornings.
There are many creative ideas out there using solar heating. One innovative application we have observed was where solar heated water was stored in water tanks which doubled as benching within the greenhouse. Like us, plants love fresh air, but not slapping winds. For many years, our flowering plants were being blown like dominoes from violent north easterly winds. Not only did this cause flower damage, it amounted to another chore to pick them all up again. Barriers to protect against the severity of these elements are essential. Ours was a simple solution – second hand galvanised iron sheeting on the eastern side of our shadehouse. Others use trays to hold pots in place.
Cymbidium orchids can be grown in as many different potting mixes successfully. There are no right or wrong answers, so long as your plants are healthy. The potting medium is required to perform a function for the plant. This includes:
Holding the plant firmly in the pot and retaining some moisture in between watering yet allowing drainage of water and salts from the pot (air filled porosity of 15-20%).
It remains the same structurally for at least two years i.e. doesn’t decompose quickly. Avoid using leaf litter or manures in the mix. Decomposing materials raise pH and absorption of nutrients is compromised.
All sorts of growing substrates have been in favour over the years. For example, coconut fibre or rock wool (in flakes, pellets or sometimes mats) or mixtures of rock wool and polyphenol foam or perlite. Commonly orchid bark is chosen, especially fine grade bark with Perlite or Lava lumps.
We use a premium potting mix with added washed river sand, perlite and gypsum. At the end of the day, remember you must find a medium which is suitable to your own particular circumstances. Growing orchids well requires an interplay between all the factors of light, temperature, water/humidity, air, potting substrate and nutrition. All are interrelated and one factor will affect the other. That is why they say growing cymbidiums is part science, and part art.
Water is essential to every living thing and essential for plant health and growth. Plants like consistency of a wet/dry cycle and prefer not to be constantly waterlogged, nor bone dry. Water thoroughly, then do not water again until the plant is light but still moist (check by picking up the pot, feel the weight).
It is no good just watering the surface of the pot. When you water, water well to make sure the potting medium is wet throughout. If you see a flow of water from the drainage holes at the bottom of your pots you have watered well. To emphasize this point, if you water your plant with a volume of 500 mm, then you want seepage through the pot’s drainage holes to be 100 – 150 mm. This method ensures a thorough watering and avoids a build-up of salts in the substrate which will damage roots.
Water regularly in spring, summer and early autumn according to temperature. If temperatures are extreme, water twice a day, if hot, water every day. If moderate, water once or twice a week. If mild, water once a week. We do not water our shadehouse plants during winter, rainfall is sufficient and the cold weather slows plant growth and water transpiration. However plants in spike and protected under plastic will be watered every week.
Smaller plants and seedlings will dry out faster than larger plants.
Quality of Water
The quality of your water is an important consideration. If your water supply contains a high percentage of dissolved salts (hard water), plant health and flowering can reduce. A tell-tale sign is seeing white salt build up around the drainage holes of your pots.
Some orchids are more tolerant of dissolved minerals than others. But grow hybrids from Cym. tracyanum and Cym. devonianum, and you can expect significant leaf tip dieback if water quality is less than ideal.
Professional growers capture water that has drained from the pot and analyse it to assess what nutrients have been utilised by the plant, and to determine any excesses. The purer the water, the better. Rainwater (or in commercial applications, reverse osmosis water) is preferred for optimal cultivation. Capture it and reap the benefits.
Nutrients for health
Nutrients come in the way of commercial fertilisers and are chemical elements or compounds necessary for plant metabolism. The purpose of fertilising is to strengthen and maintain every aspect of a plant’s health. The inner workings of plants are truly remarkable with literally thousands of reactions involved in keeping the plant alive and in good health. The three major nutrients required are:
Nitrogen for promotion of growth.
Phosphorous for root and seed development.
Potassium for flower production.
Other elements required in significant quantity are Sulphur (structural component in amino acids, vitamins and enzymes), Calcium (structural component of cell walls), and Magnesium (part of the chlorophyll molecule). In addition, cymbidium orchids require small amounts of the trace elements, and deficiencies of any of these will show up in a discolouration of the leaves, and poor resistance to pests and diseases.
Nutrition is one of the cornerstone keys to success but remember, without light for photosynthesis, and a strong root system to enable water to be made available for photosynthesis, the uptake of nutrients will be compromised.
During growth periods (temperature ideally above 25 C), you can fertilise at every watering. We administer fertiliser through the overhead watering system (injected into our water supply). If you don’t have a dosatron or similar, purchase a sprayer with attachment that allows for an injection of fertiliser as you water.
What fertiliser do we recommend? For small collections, purchase a generic fertiliser suitable for cymbidiums. Refer to our later chapter, our Eight Tips for cymbidiums, and we reveal what fertiliser we utilise, and why.
A pH too high or too low will affect the availability of nutrients to your plants. Ideally cymbidiums like a pH between 5.2 and 6.2. Slightly acidic, much the same acid level as a banana milkshake.
When the temperature warms and vegetative growth increases in spring and summer, plants can almost double in size.
For young plants an annual or biannual cycle of repotting into a larger capacity pot is recommended, preferably anytime except winter. Most of our repotting is done in early spring, giving time for plants to establish themselves in the new container before the rigors of summer.
Now here’s a secret. Experience tells us that placing a plant in a pot too big (compared to the plant) may actually impede growth and flowering. The bigger the pot, the greater the water holding capacity and the plant goes into establishing itself in the new medium. An overpotted plant may get too wet and not undergo the wet/dry cycle cymbidiums require. Then the orchid’s roots struggle to cope with an overload of moisture, water-logging is, in essence a kind of suffocation. Without air, roots rot.
Conversely if plants are neglected and remain in the same pot for years, the resulting root ball deprives it of water – moisture runs off rather than soaks into the container. What we do is pot up at least once a year (ensuring the plant is growing well) into a pot marginally bigger than the one it came out from.
The secret is to know when a plant is snug in its pot erring on pot bound but not so tight it is deprived of water and air.
Plants with a solid root system are more likely to flower.
If a mature plant has outgrown its pot, or has pseudobulbs hanging over the rim, it is time to consider whether to pot up or divide. If the pot feels firm to squeeze, then most likely the root ball is tight. If this is the case, go up in size.
If the pot squeezes easily, the root system may be lacking and potting up into a bigger pot will not help the plant establish itself with vigour. Repot with fresh mix in the same sized pot, or if necessary, pull away old roots and backbulbs and pot into a smaller pot.
If however, you believe the plant is not a good grower despite your best efforts, cull.
Choosing the right pot size is important. The secret is to decide on pot size according to the root ball. Choose a pot which is slightly bigger and no more than one third deeper than the root ball. Place the root ball in the centre and infill and tamp down around the plant. You should see about one third of the bulbs are under the mix and the plant is nice and snug with room for the roots to grow and breathe.
Pests and Disease
We are certain good culture is the first line of defence. The superior growing plants seem to have greater resistance to disease and pests. Check the environmental factors – light, temperature, air, water and nutrition first and foremost and you should not need any fungicides or pesticides on your plants.
If your conditions are too bright and dry, mites love these conditions and can attack the underside of leaves. Hydrate and spray under the leaves if you see their spidery effects.
Too crowded a nursery deprives plants of light and their resistance goes down while their susceptibility to scale attack increases.
It is important to select plants that possess disease resistant genetic heritance. As commercial growers, we are only interested in the strongest plants and cull slow growers and runts, irrespective of genetic potential.
Third, we clean our shadehouse as often as time permits. The time spent raking leaves, removing husks, sweeping paths and ensuring a weed free environment pays dividends in the avoidance of heart-breaking or back breaking remedial action some months later.
Finally, scale can set in where plants too close together. Mites thrive in a warm dry environment. However, these two problems are avoided by the simple measures of adequate spacing and watering according to need. Not only can weeds deprive a plant of water and nutrition, they can harbour pests. Butterflies lay eggs on weeds, so it is important to keep surrounding areas weed free to minimize caterpillars. Slugs and snails can be a problem. They are minimised with metal or plastic benching and if necessary, the application of snail bait after rain. It is best to do this when spikes are forming, or well before buds emerge from the sheath.