Growing Orchids

Author: Angela van Rooyen

In this orchid world of ours, it is always dangerous to talk or write about culture as we all have our own ideas which we firmly believe in. Emerson Doc Charles from California, after whom the beautiful Paph. emersonii was named, has a notice on the wall of his green house: DO IT THE RIGHT WAY - MY WAY.

This article will discuss the basic principles of orchid culture which we all know and use and there may be a few new ideas, collected from our many orchid friends around the world, which might interest you.

But, it your orchids are growing and flowering well , don't listen to other people - just go on doing what you are doing. Success in orchid growing is not having all the latest equipment and techniques, but in doing the right thing in your conditions with what you have.

What is the most important element needed for growing orchids?

Water. Good water. How do you know if you have good or bad water?

There is only one way. You have to have your water tested so that you know what the pH is (the acidity level ) and what else it contains. Water problems can be rectified, but you can't do anything about it if you don't know that you have a problem.

Water pH?

Why is pH so important?

Plants cannot absorb certain nutrients and elements from the soil if the pH is too high - above 7 which is alkaline - or, if the pH is too low - acid - below 5. A pH measuring 7 is neutral, but orchids grow better in a slightly acid medium, the ideal being around 5,6.

How can you change the pH of your -water? If pH is too high - above 6 - add phosphoric acid.

If pH is too low - under 5 - add potassium bicarbonate.

Be sure to use plastic or polythene pipes if you have acid water as the acid can act as a solvent and release zinc or copper from galvanized or copper pipes and cause toxicity to plants.

Your water can be soft or hard (this has nothing to do with pH).

Hard water contains a high concentration of salts, especially Calcium and Magnesium, and this is the most frequent problem that orchid growers have. Hard water will leave a calcareous residue on leaves reducing the available light and slowing growth. Calcium deposits on orchid leaves due to hard water, can be removed by wiping -with a sponge dipped into lemon juice which cleans off unsightly deposits and gives the leaves a lovely silky appearance.

Never use water from household water softeners for your orchids as it is too high in sodium which is toxic to plants.

What can you do if you have hard water? (water with a high salt content)

  • Install a demineralizer or reverse osmosis system. This is impractical as it is far too expensive.
  • Leach out pots once a month by giving lots of water.
  • Lower the pH to nearer 5 than 6. This will make the salts more soluble and thus more leachable.
  • Repot frequently - every year instead of every 3 years.
  • Ensure good drainage of pots by crocking and enlarging drainage holes.
  • Use non-porous pots - plastic instead of clay.

Are there any good aspects of having hard water?

Yes. Good if your potting medium is acid and beneficial as it supplies calcium.

Soft water

What about lovely soft water, meaning water with a low salt content?

Here you have a potential problem of Calcium, Magnesium or Iron deficiency.

Watch for signs and supplement these minerals it necessary.

Is water temperature important?

Watering your orchids with very cold water can lead to cell collapse in delicate new leaves and cause die back of those all important root tips.

On really hot summer days, it is best to water early morning or late afternoon as cold water on hot plants is such a shock to the plant that it stops growing for a few hours.

Rain water

Rain water can be wonderful or laced with harmful chemicals - depending on where you live. It can be very acidic if you are in an industrial area, so, once again, have your rainwater tested too.
  • Do not collect and re-use greenhouse irrigation as this is a sure way to spread disease.

When do you water your plants?

Hopefully not every Monday or perhaps Saturdays when you are home from work. Weather changes make it impossible
to have a set routine for watering:. You water when the plants need it. How do you determine that? Often a plant looks bone dry on top and when you tip it out of the pot, the mix is actually still very wet towards the bottom. A good way of testing it the plant is dry, is to pull out the label and feel whether it is wet or dry.

Another method is to have a tester pot, the same size, full of the same mix, but without a plant in it, on every bench. When in doubt whether you should water or not, tip the mix out and you will immediately see it needs watering or not. Bear in mind that the pots containing plants will dry out sooner because the plants are using water. Return mix to the tester pot quickly, before it has time to dry out, and place back onto the bench, ready for next time.


Vitally important for good orchid growing. Ideally the humidity should not drop lower than 65%, but this is not always easy to maintain.

You can install:
  • A fogger system
  • Humidifiers
  • Sprays under the benches
  • Or simply just wet the floor a few times a day.
  • A broken surface, like gravel, has more areas that can evaporate than a cement floor and is therefore preferable.


This is not a technical paper, and we shall not discuss fans and their opacities, and the delicate balance between ventilation and humidity.

Do you have enough INTERNAL air movement for your orchids - especially if it is cold and all the doors and vents are closed? You must have a fan or some sort of system that circulates the air in the greenhouse and runs all night.

Stagnant air allows spores of fungi to settle and grow more easily.

You can have air movement reaching all your plants with just one little fan blowing into a plastic tube that has holes cut or burnt into it at strategic points to let the air out and is placed on the floor under the staging. The cool humid air is then circulated instead of hot dry air when the tubes are hung under the roof.

Internal air movement solves the problem of damp or dry comers developing in a greenhouse.


A discussion of individual types and brands would be a book on its own, but consider the following.

What is the most common problem with fertilizing? Calcium deficiency

How do you recognize a Calcium deficiency? It can easily be confused with sunburn - the leaves blacken at the tips and this black area can spread to the whole leaf. Sometimes there is a yellow band between the black area and the green leaf called a halo. This die back can occur in the new and old leaves but usually happens in younger leaves and mostly in summer. In Cattleya the whole leaf eventually goes black and then falls off - very much like Tobacco Mosaic Virus (TMV) in Cattleya where the leaf also goes black and falls off. The difference is that TMV starts with black sunken spots all over the leaf and not only a black band at the tip of the leaf.

The leaf tips go black because, as a result of the calcium deficiency, the turgor pressure in the cell sap is so low that the plant is not able to push nutrients to the tip of the leaf.

The remedy is simple:
LIME - and preferably dolomitic lime as it contains magnesium too.

Sprinkle all your orchids with dolomitic lime 5 or 4 times a year - starting with about half a teaspoonful on small pots increasing to a tablespoon on very large pots.

The European growers prefer to use a solution : 2 grams dolomitic lime per litre of water 5 or 4 times a year. You have to stir or agitate this mixture called 'kalkmilch' continually as it does not dissolve completely. Don't worry about unsightly blobs of white all over your plants - it does no damage and disappears after a few waterings.

The result is amazing. When growing in bark, after about a year, the pH of the medium in the pots, has probably dropped to below 5 which means that the plant can not absorb all the lovely nutrients you are diligently giving it. When bark starts to break down, it also uses nitrogen for this process, leaving less for the plant. Sprinkling dolomitic lime, or giving the lime milk, raises the pH, the fertilizers again become available to the plant and your orchids look greener and happier.

Yellow leaves

If the leaves are still yellowy, a wonderful tonic is to spray your plants with a WEAK solution of liquid nitrogen - urea - calcium ammonium nitrate - in the LATE afternoon, just like a light foliar feed and watch how they green up after only a few days.

Cymbiduim. growers often say they like their plant leaves to have a pale green colour as it shows they are getting enough light. Cymbidium leaves can be green, even if grown in full sunlight. If pale green, they need more food. Increase the fertilizer strength or feed more frequently.

Miltonia and Odontoglossum leaves are naturally paler green. They produce red pigments and sometimes a red edging round the leaves when exposed to strong sunlight. If Miltonia and Odontoglossum leaves are yellow or paler green than normal and without any red pigments, it is usually a sign of nitrogen deficiency and not of too much light. Once again, increase strength or frequency of fertilizer. Iron chelate is a good additive and don't forget the dolomitic lime.

Leaf tip burn

This must not be confused with sunburn which is easily recognized as it always occurs on the highest part of the leaves - sometimes the tip of the leaf or else in the middle part if the leaf is lying horizontally and that part catches the most sun.

Fertilizer burn.

If most of the leaf tips of an orchid are brown, there is trouble at the roots. Up the plant out of the pot and examine the roots. You will probably find dead root tips or brown damaged roots that have discoloured because of fertilizer burn due to salts building up in the potting medium. This can be remedied by leaching out your pots with lots of water once a month. Check die strength of your fertilizer.

Pests and diseases

Pests and diseases are unfortunately part of growing. The most damaging of all pests for our orchids are probably scale, mealy bug, slugs and snails.


Scales are difficult to treat. There are two types:

Armoured type - Boisduval scale -
(Diaspis boisduvalii). Protected from insecticides by their waxy hard armour covering.

Soft scale (coccus hesperidium) and also Mealy bug (Pseudococcus longispinum).

These pests are protected by cottony woolly secretions which guard them against the effect of poison, so you have to use a systemic insecticide or an oil spray like oleum that smothers the scale.

All scales feed by sucking nutrients from the plant and they cause tremendous damage.

If you see yellow areas on the leaves, look underneath them and you will probably find colonies of scale or mealy bug.

They should be eradicated as soon as possible as they breed rapidly. Mealy bug females lay 100 to 200 eggs that hatch out within 2 -weeks.

Soft scale and mealy bugs excrete honey- dew which ants love and they visit plants in search thereof. This honeydew is also an excellent medium for sooty moulds. If you see ants or black sooty moulds on your orchids, examine the plants carefully for scale or mealy bug, especially on the underside of the leaves and in the axils. Spray with the appropriate insecticides. If you have a light infestation, methylated spirits and a small paint brush may be sufficient to kill a few small colonies starting up, but act immediately.

Just a reminder to remove dead and yellow leaves, old flowers, and, if you are really desperate, even the flower buds, before you spray. They don't absorb insecticides and all the clever insects will quickly move to the dead leaves to get away from the poison and live happily on. And this goes for systemic insecticides too.


are easy to get rid of as they are sensitive to most insecticides and even soapy water. Once again, act quickly as they have a short life cycle and are fast breeders especially in hot climates. It has been proven that aphids can transmit yellow bean mosaic virus but fortunately this virus seems to affect only Pleurothallids. Growers of Masdevallia , Dracula, Restrepia and others in this fascinating subtribe, should never have a single aphid on their plants.

Apparently orchids collected from nature, never have scale. The same is said about virus. No jungle collected plant has ever tested positive for virus. What are we doing that we are spreading these infections and infestations amongst our plants?

IMG 4916 small
Spraying insecticides and fungicides:

Never spray dry plants.

Don't keep any sprays that have been mixed to use again later. They deteriorate when diluted and you are wasting precious time and money.

Never spray during the heat of the day or if very cold.

If hot, over 25°C, the spray evaporates too quickly, concentrates and can cause plant burn. If under 17°C, red spiders are not active and can hide from the spray. Use a miticide for red spider and be sure to spray the underside of the leaves too and repeat the process two or three times at weekly intervals. We repeat spray for all pests and snails (except with systemics) as the spray does not kill the eggs and we want to eradicate the new generation before they are old enough to lay eggs and start the reproductive cycle all over again.

False spider mites, also known as Citrus Flat Mite (Brevipalpus callfornicus) live on top of the leaves in which they cause tiny pits , especially on Phalaenopsis).

The interesting occurrence with false spider mite infections, is that opportunistic fungi can now enter the leaves through these little holes made by the false spider mites and cause black spots which can easily be mistaken for a primary fungal infection. So what do we do - we spray for fungus which is actually the secondary problem here and the damage continues. If you see small sunken areas on top of the leaves, as well as brown fungal spots, treat with insecticide and fungicide and I specifically say insecticide as FALSE spider mite is not a mite and a miticide will not solve the problem.

Aerosol sprays

What about aerosol sprays? There are all sorts of handy cans on the market and it is so easy just to pick one up and give a quick spray if you see an intruder or a suspicious looking black spot. The problem is not the contents of the can, but the distance it is held from the plant. You will get phyto-toadcity if applied at less than 50 cm between the aerosol nozzle and the plant. 23 plant sprays were tested. They were ALL toxic to the plants at 20 cm but only 2 caused injury at 40 cm. Allthe brands damaged plants when used at temperatures above 38°C.

Fungi and Bacterial diseases

There are many different leaf spots but the most important point here is to try to avoid them, as getting a severe fungal or bacterial infection is the worst thing that can happen to your orchids.

Prevention is better than cure. How?

Above all hygiene and cleanliness. Don't leave decaying plant matter lying around the greenhouse - spores of fungi and bacteria are always present in the atmosphere and they will thrive if given the ideal conditions.

What are the ideal conditions for them to multiply?
  • Poor circulation
  • High humidity
  • Somewhere to breed - old decaying leaves and broken down compost
The nozzle of your hosepipe lying on the ground is inviting spores to enter and just think how you are spreading them when you start watering. Always hang the end of your hose against the staging or anywhere away from the floor.

Brown spot

The most common and severe disease you can get, is bacterial brown spot. The first sign is a soft watery area on the surface of the leaf (especially on Phalaenopsis and Paphiopedilum) with brown droplets oozing out. If left, the area turns brown. This dreadful disease is spread when you water your plants so you have to remove the spot Immediately. Cut out the infected area of the leaf and, whoever you do, don't throw the piece down on the floor or even in a rubbish bin in your green house. Get it away from your plants as soon as possible. The same goes for those nasty smelling rotten insides you sometimes pull out of the new Cymbidium shoots. Best is to carry these pieces of infected tissue out in a plastic bag or else you are spreading deadly spores all over your green house.

Dust the infected area and cut edges with 'flowers of sulphur' or soak the whole plant in a fungicide / bactericide.

black rot on vanda

We have wonderful natural fungicide in the form of cinnamon and it is so handy to have a few little bottles standing around in your green house. If you notice a fungal problem starting, first give it a generous dash of cinnamon powder. This spice dries the area thereby preventing the disease from spreading.

Spray the inside of your orchid house roof at least once a year. Condensation. drips off the roof onto the plants and can spread fungal and bacterial diseases.

Take great care when spraying. We can never be too cautious when working with insecticides and fungicides - they are tpxic and we must not become casual in our approach towards using them.

Always wear protective clothing and don't eat while spraying.

Stick to the recommended dosage - don't think you are going to kill the insects quicker if you make the poison stronger. You can't be half dead and you also can't be deader than dead.

Slugs and snails

Slugs and snails are every orchid growers nightmare.

Metaldehyde is the active ingredient in all molluscicides - the poison that kills slugs and snails. There is a suspicion that metaldehyde may cause sterility. We all use these pellets and liquid snail killers but is there anything else that is safer and will help to limit these damaging pests that feed on buds, flowers and lovely juicy new roots?

Snails and slugs prefer habitats offering shelter, moisture and food. They are nocturnal, not because they like darkness, but they prefer lower temperatures and moisture. That is why we see them out on cool days. Important in their control is :
  • Sanitation
  • Destruction of hiding places
  • Removal of refuse
Get rid of ground covers and other companion plants grown under the benches - sadly!

Metallic copper barriers - The theory is that slugs and snails don't like to crawl over copper. Use copper wire around the legs of your staging or the copper masking tape that has just become available.

A blob of cotton wool round the stem of a precious bud, will save it from being literally nipped in the bud.

Jeyes fluid is also a deterrent. Use 50 ml of Jeyes Fluid per 5 liters of water and pour this over staging and floors once a month. Use 15 ml of Jeyes Fluid per 5 litres of water if you want to douse the plants as well.

Water the plants with an infusion made from the berries of the Syringa tree.

If the stubborn pests are still causing a lot of damage, you will have to revert to a dose of poison repeated twice at weekly intervals. The methylcarbonate combination probably works the best. It is available in pellet or powder form. The powder can be used as a dust or made into a solution using 1 gram per liter of water. The liquid solution has the added advantage of treating the compost as well which is the favourite hiding place of slugs and snails.

Don't make the mistake to kill those big garden snails that can grow to 15cm (Agathina imaculata). One would think that such a huge snail could devour a
whole orchid plant in one night, but actually they don't eat living plant material but live on decaying and rotten organic substances. There is another snail called natalina, that live  in a beautiful olive green and yellow shell, cam be 7 - 8 cm long and eats only snails.The natalina - about 7 to 8 cm long. They follow the slime trails which contain ferro hormone combinations and lead them to where the snail is hiding. Wouldn't it be wonderful if we could catch a few of these and keep them as pets in our orchid houses.


Many growers hang their orchids in baskets to keep them out of reach of snails and because some grow better in baskets. Just a word of caution - beware of some types of wire. The Eric Young Orchid Foundation lost their Stanhopea due to toxicity of wire baskets. You would be safer using plastic coated wire, wooden or non toxic metal baskets.


This is a controversial subject . We all know that we must be careful not to spread this incurable disease by using the same cutting instruments, before we have sterilized them. There seems to be some difficulty in deciding whether chlorotic streaks in the leaves are caused by a virus infection or a mineral deficiency. Virus presents itself as yellow streaks, often in the shape of a J or a V, or in mosaic patterns, in the new leaves.

The problem is that it is sometimes only at a certain stage of the development of the new growth and then these telltale marks can disappear. Also, good culture masks virus but when plants are stressed or divided, or exposed to high light intensities, the virus shows up.

V markings in old leaves, can still be confused with a mineral deficiency, but not in a new growth. Even if a plant is suffering from severe mineral deficiency, it passes all the available food to the new growth and therefore chlorotic marks in a new lead are very suspicious of virus.

This remark about orchids passing all the food to the new growth, is very interesting to Cymbidium growers. If your Cymbidiumm plants have too many backbulbs, the logical conclusion is that they are not getting enough food. The plant gives the limited supply of nutrients to its active growing part - the new lead. The leaves from the older bulbs drop off because they don't get enough food to keep them living . Result: too many leaf- less bulbs. If adequate food is available, a Cymbidium should retain it's leaves for many years.

If I can leave one final important growing suggestion with you, it will be HANDLE EVERY PLANT IN YOUR COLLECTION EVERY YEAR.

IMG 3282 smallAnd by handle, I mean MOVE IT - even if you move it only 20cm. Your reaction will probably be that this is impossible and impractical as you have
too many plants. Gallub and Stribling, the famous Cym.bQium. growers at Santa Barbara in California, have 18 hectare of plants - mostly huge Cymbidium - and every plant gets moved yearly. Why? To examine the plants. The only way to really look at a plant, is to pick it up. One thing is certain - if you don't move the plants, you are not going to pick up every pot.

Now what is so important that you have to go looking for? The label

Is it still legible? How many of us have lost names of plants because we didn't realize that the so called 'permanent' ink, was fading after being exposed to our harsh South African sun for a few years. We find that an ordinary HB pencil lasts the best.

Read the label. Has the plant been regis- tered since you purchased it - then you could add the new name to the label.

Consider if you want to keep the plant or sell it or give it away or even throw it away if it is a poor specimen. Then do it.

Have you promised somebody a division of the plant, then give it.

Look at the pot size. Can the plant grow in this pot for another year?

Is the potting medium still good enough or has it broken down? Set aside for repotting if necessary.

Examine the plant

Are the bulbs hard and the leaves healthy and disease free? Feel if the plant is secure in the pot. If not, your plant has trouble at the roots. Tip it out of its pot and examine the roots. If they are firm and active, put the plant back into the same pot. If there are soft roots or the mix seems to be decaying, clean up and repot into new mix. We should look at our plant roots more often - don't forget: WHEN IN DOUBT, TIP IT OUT.

Time to repot.

We have looked at our plants, but it is just as important to walk through your orchid house and, for once, forget about the plants arid look at the growing area. Just be aware of what you SEE and what you FEEL. We find this a strongly developed sense amongst older and more experienced growers. George Vasquez's father, Amado, told us that he can tell the exact percentage of humidity by looking at the hairs on his arms. I can smell it - but not exactly. What anyone can sense and must be aware of, is a change in light intensity when walking in a plant house. Look up and for sure there will be a patch on the roof where the paint has washed off or a darker area where some leaves have dropped onto the roof or your neighbour's tree is casting a shadow.

There are two ways of dealing with these irregularities - correct them, or use them by moving the plants to make full use of the micro climates which you find in all plant houses. Just think of the areas near the door. In a cool house, it is going to be warmer near the door because of hot air rushing in every time it is opened. Most certainly the door areas of a heated house, will be colder. Be aware of these variations in your growing space and use them for the plants that prefer those conditions.

Before we leave the orchid houses - try to keep them neat and nice. Don't leave old labels lying around - you would not want your friends to see how many plants have died! Remove dead leaves and old blooms as dying flowers give off ethylene gas which causes the other fresh flowers to wilt more quickly.

Share your orchids with others - I can't tell you how many people have said : this is the first orchid I have ever had.

Love and enjoy your orchids and be aware that God speaks to us through His creation. Never lose the wonder and magic of seeing a new orchid hybrid flowering for the first time, or an old plant you had forgotten about, bravely pushing up another bud to remind you that some of the oldies are still as beautiful as the best of today.
Happy growing.
Angela van Rooyen
PO Box 646
White River
South Africa
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