© Angela van Rooyen
Extracted (with permission)
from SAOC Yearbook ORCHIDS South Africa 2000
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 white Paph.
emersonii was named) has a notice on the wall of his green house: "DO IT THE RIGHT
WAY - MY WAY".
Here we will discuss some of 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, if 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 is doing the right thing in your
conditions with what you have.
the most important element needed for growing orchids?
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. You need to know the pH (the acidity level) and also what
minerals and other elements your water 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 galvanised and copper pipes and cause toxicity to plants.
Your water can be soft or hard (this has nothing to do with pH)
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 content which is toxic to plants!.
What can you do if you
have hard water?
(that is water with a high salt content )
» Install a
demineralizer or reverse osmosis system which is impractical as it is far too
» 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
» Repot frequently - every year in stead of every 3
» 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. Hard water is good if your potting medium is acid and beneficial as it
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 if
Is water temperature important?
Watering your orchids with very cold water can lead to cell collapse in delicate
new leaves and also 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.
One is always tempted to give your orchids a spray of lovely cool water
or open the sprinklers when very hot, ' to cool them off '.
It has taken us many years to learn that we are actually causing more harm
than helping the plants. If leaves are wet, the stomata on the undersides of the leaves
will close and photosynthesis will stop. This can cause the leaf to overheat as it cannot
cool itself by the normal process of evaporation and thus growth is slowed down.
can be wonderful or laced with harmful chemicals - depending on where you live.
Rainwater can be very acid if you are in an industrial area , so , once again, have your
rain water tested too. How do you store it? Avoid galvanized or tar lined tanks.
» 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 if
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 if
it needs watering. 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.
is 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
» sprays under the benches
» or simply just wet the floor a few times a day.
A broken surface, like gravel, has more
surface areas which can evaporate, than a cement floor, and is therefore
This is not a technical paper and we shall not discuss fans and their capacities 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 green house. There should also be a fan that 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 fan blowing into a plastic tube that has holes cut or burnt
into it to let the air out at strategic points. The tube is placed on the floor under the
staging. The cool humid air from the floor is then circulated in stead of hot dry air as
happens when the tubes are hung under the roof.
» Internal air movement solves the problem of damp or dry corners
developing in a green house.
which we are not going to discuss as that is a book on it's own. All fertilizers
contain the basic nutrients: nitrogen, phosphate, and potassium in different combinations
plus other elements needed for plant growth.
What is the most common problem
How do you recognize a calcium deficiency?
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 Cattleyas the whole leaf eventually goes black and then falls off - very much like
Tobacco Mosaic Virus (TMV) in Catts, 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.
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.
LIME .... and preferably dolomitic lime as it contains magnesium too.
Sprinkle all your orchids with dolomitic lime 3 or 4 times a year - starting with about
half a teaspoonful on small pots and increasing to a tablespoon on very large pots.
The European growers prefer to use a
solution: 2 grams dolomitic lime per liter of water 3 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 so diligently giving it. When bark starts to break down, it also uses nitrogen for
this process, leaving even 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.
If the leaves are still yellowy, a wonderful tonic is to spray your plants with a WEAK
solution of liquid nitrogen in the form of calcium ammonium nitrate, in the LATE
afternoon. Watch how they green up after only a few days.
Cymbidium 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
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. The
heat of the sun burns a brown oval patch which eventually goes dry and black and does not
If most of the leaf tips of an orchid are brown, there is trouble at the roots. Tip
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 the strength of your fertilizer.
can also die if your potting mix has broken down or the drainage holes are insufficient,
or because of disease such as phytophtera.
It is important to stop fertilizing a
few weeks before you stop watering those orchid plants that need to be dried out in
winter. If you don't do this, you can also get fertilizer burn due to the salts in the
pots concentrating as the mix dries out. The brown leaf tips are not the actual damage,
but an indication that the roots have been burnt. The principle here is the same as with
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
boisduvallii) They are protected from insecticides by their waxy hard armor covering
Soft scale (Coccus hesperidium)
Soft scale and mealy-bugs (Pseudococcus
longispinum) are protected by cottony woolly secretions, which guard them against the
effect of poison.
For these pests 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 irradicated 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
honeydew 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 as well as old flowers before you spray. They don't absorb insecticides,
(even systemics ), and all the clever insects will quickly move to the dead leaves to get
away from the poison and live happily on.
are easy to get rid of as they are sensitive to most insecticides and even soapy water will kill them. 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?
insecticides and fungicidesDon't keep any sprays, that have been mixed,
to use again later. They deteriorate when diluted and you are wasting precious time and
Never spray dry plants.
Never spray during the heat of the day or
if very cold
If hot (over 25 degrees C) the liquid spray evaporates too quickly, concentrates
which can cause plant burn. If under 17 degrees 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 irradicate the new generation before they are old enough to
lay eggs and start the reproductive cycle all over again.
spider mites (brevipalpus
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
So what do we do wrong: 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 therefore a miticide will
not solve the problem.
What about aerosol sprays? There are all sorts of handy aerosol cans with ready
mixed insecticides and fungicides 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
You will get phyto toxicity 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 two caused injury at 40 cm. All the brands damaged plants when used at
temperatures above 30oC.
and Bacterial diseases
There are many different leaf spots, but the most important point with these
diseases, is to try to avoid them. Getting a severe fungal or bacterial infection, is the
worst thing that can happen to your orchids and prevention is better than cure. How?
Above all hygiene and cleanliness
Don't leave decaying
plant matter lying around the green house - 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 air circulation
» High humidity
» Old decaying leaves and broken down compost
(somewhere to breed)
» The nozzle of your hose pipe 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 the
hose against the staging or anywhere away from the floor.
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 paphiopedilums) with brown droplets oozing out. If left, the area
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. Don't throw the piece
down onto 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
Dust the infected
area and cut edges with flowers of sulphur or soak the whole plant in a fungicide / bactericide.
We have a 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, just give it a generous dash of cinnamon
powder. This spice dries the area thereby preventing the disease from spreading.
Added bonus - appetising pancake smells in your green house.
Spray the inside of your orchid house roof with fungicide 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 toxic to
people 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 -
every orchid growers night mare.Metaldehyde is the active
ingredient in molluscicides - the poison that kills slugs and snails. Researchers are
concerned that metaldehyde is harmful to humans and there is even 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 factors in the control of
slugs and snails
» Destruction of hiding places
» Removal of refuse
» Get rid of ground covers and other companion plants grown under benches
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 30 ml of Jeyes Fluid per 5
liters of water and pour this over plants, staging and floors once a month.
» Syringa tree. Water the plants with an infusion made from the berries of the Syringa
tree. (Melia azederactera) Keep children away as syringa berries are poisonous.
» 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 and 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 lives in a
beautiful olive green and yellow shell, can be 7 or 8 cm long and eats only snails. The
natalina follows 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.
If you have a small collection, the best and most satisfactory way to get
rid of snails, is still to catch them.
Place lettuce leaves, strips of carrot or even
squeezed out orange halves, left over from juice
making, on the pots in the late afternoon. Go back later in the evening, or even
very early the next morning, and you will find the slugs and snails on the fruit and veg.
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 stanhopeas 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 markings in the
leaves are caused by a virus infection or a mineral deficiency. Virus presents itself as yellow or bleached streaks, often in the shape of a J or a V, or in mosaic or
circular patterns, in the new leaves.
The problem is that these tell tale
marks are sometimes obvious only at a certain stage of the development of the new growth
and can then disappear. Also, good culture masks virus but when plants are stressed,
divided, or exposed to high light intensities, the virus shows up. As the leaves get
older, virus markings become darker and more obvious but the plants should have been
destroyed before this stage.
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.
"Orchids are passing all the food to the new
growth"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 bulbs without leaves. If adequate food
is available, a cymbidium should retain it's leaves for many years.
This remark about orchids passing all the food to the new growth, is
very interesting to cymbidium growers. If your cymbidium plants have too many leafless
back bulbs, the logical conclusion is that they are
If I can leave one final
important growing suggestion with you, it will be:
EVERY PLANT IN YOUR COLLECTION EVERY YEAR
And 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 cymbidium growers at Santa Barbara in
California, have 18 hectare of plants - mostly huge cymbidiums - 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?
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 registered 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.
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.
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 and 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 the way the hairs on his arms react when
he enters an orchid house. 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
A final word of caution. Examine
any new plants carefully as you don't want to bring pests and diseases into your
orchid house. Treat for slugs and snails in any case, as you won't see them during the day
however thoroughly you look.
Share your orchids with others
- I can't tell you how many people have said:" This is the first orchid I have
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.
Angela van Rooyen
Associate Member of COS
permission) from SAOC Yearbook ORCHIDS South Africa 2000
ORCHIDS South Africa 2000 is available from SA Orchid Council