This culture section
is written to give an overview for growing orchids indoors that may not be immediately
apparent from general orchid literature. There are subtle differences when orchids
are grown indoors compared to greenhouse culture. Many books are written for
people living in southern
Disclaimer: The
information I have given here is collected from my 20 years or so of orchid
growing experience and I don't guarantee any results or techniques whatsoever.
These culture notes are based on my experience of growing orchids in an air
conditioned (A/C) office room in Seattle,
I thoroughly recommend
some beginners books on Orchid Growing, these are 'Taylors Guide to Orchids' by Judy
White and Ortho's 'All About Orchids'. Another book is 'Orchids for Everyone'
which is probably more easily available in the
For more detail
on high light orchids, David Grove's 'Vandas and Ascocendas' is excellent, giving
great detail on watering and feeding regimes plus it has lots of good pictures
of Vanda breeding and the pursuit of hybrid excellence. The book is useful even
if you don't grow Vandaceous types since the advice applies to Cattleyas, Dendrobiums,
etc.
The three most
important aspects to growing orchids successfully are:
Orchids will flourish
and flower beautifully if the environment is ideal for them. If you could produce
a growing room that was warm and humid with gentle air movement and filtered
sunlight with a good temperature drop at night your orchids would grow fast
and flower regularly.
This is what I
mean about environment, if the general conditions of light, heat, air movement
and humidity are correct and you water correctly you will have great plants
and flowers. In addition, if you match the potting and compost to the environment
also, this will help with better plant growth and an easier time of growing
them. So if you have high humidity (i.e. damp), use open pots with good drainage
and a compost with a resistance to breaking down. If
you have low humidity, use a closed plastic pot (i.e. no side holes) and a more
retentive mix that provides local humidity in the pots.
However, back in
the real world of windowsill growing, the environment rarely is ideal although
windowsills can be good enough to flower most things. However, you shouldn't
expect to match the greenhouse growers with plant size and flower quality. The
main problems you may encounter are lower light levels for periods of the day
than are ideal, and sometimes higher light levels than ideal when the sun shines
direct through the windows, lower than ideal humidity and possibly lower or
higher temperatures than the ideal at some stages of the year.
Always try to match
the type of orchids that you grow to the environment if you cannot alter one
ore more of the basic environment parameters. Remember also that light can be
adjusted a bit easier and certainly at lower long term cost than basic heat
problems. Since the temperatures where I grow are beyond my control I chose
to grow warm orchids, it would be useless for me to try to fight the environment
for example and grow Masdevallias. These plants like it cool and damp. Thus
it is important to understand your conditions before you build up a collection,
and you must choose plants that suite your conditions.
The light levels where I grow indoors are ALWAYS less than ideal. However, this doesn’t mean that high light orchids cannot be flowered. You just have to be bold and push the plants closer to the windows with less shading than you might think.
In one location I had windows only facing West, that meant that I got no sun whatsoever until 1pm. Once I did get sun, it was quite hot and very sunny, thus best suited to Cattleya types. This meant that the plants got very low light until 1pm, then too much light according to the books after 1pm. I was able to borrow a very high quality light meter from my local society which helped me to understand what was happening. Vandas were a problem even with growing the plants directly in the windows. Outside, readings of 11000fc were taken in full sun. Inside, 3700fc. This means that indoors in what appeared to be full sun with no apparent shading, the glass and its coating and dirt were reducing the light by 65%. In other words, I had 65% shading. This combined with only getting strong light after 1pm meant they didn't spike easily at all. (My solution with the Vandas was to grow them outdoors on my deck in Seattle from June 1st through Sept 1st and all of them finally spiked).
Where I now grow in the UK indoors I have East and West facing windows, again I place the plants in "full sun" direct in the windows. The light readings indoors in sun are over 5000fc, when there is no sun they are around 100fc (50x less). Again, this indicates I now have about 55% shading effect from the window glass alone since outside the readings are 11000fc. Of course indoors in this East and West aspect the plants only get a half day at most of sun which is why this method works.
In summary what this all means
is I typically give plants something like +10 to +30% higher light levels than
usually recommended, but for shorter periods to compensate for the higher levels.
If I were to give the plants these light levels (+30%) for a full day e.g. in
a South facing window, I would get burn and bleached leaves indicating too high
light and maybe also somewhat stunted shorter growth.
Indoors, I apply no other
shading to my plants, the Phalaenopsis are moved back
a bit and shaded by other plants. I grow the Paphiopedilums in "full sun"
and have had no burn at all, not even any bleaching. (Also see comments
below about the air movement, A/C and temperature).
When making light adjustments move the plants slowly towards increasing light, don't just dump them into a very sunny window, they may well burn. Do it slowly over a matter or a few weeks, gredually increasing the light and use a fan to control leaf temperature.
The photo below
gives shows the A/C office where I used to grow with West facing aspect. Note
there is no additional shading.
An Indoor Growing Room in Seattle, USA
The temperatures
in some of my growing locations have also been outside my control. In the A/C
office they varied from a winter low of 63F to a winter high of 70F, in summer
a low of 70F and a high of 85F were normal. I could rarely get the ideal low
temperatures in winter to encourage spiking, but managed OK. On a sunny day
the temperature rose at night when the A/C switched off and the latent heat
in the building was released.
The one actual (and only) bonus of A/C is that the plant leaf temperatures are unlikely to get too high. In other words, the cool air stops the leaf temperature rising despite the fact there is direct sunlight on the leaf and thus no burn occurs. I also had a fan going whenever the sun was in the room to distribute the air and lower leaf temperatures. Again, this is why I can grow with higher light levels that are normally prescribed because the leaf temperature cannot get to dangerous levels I use fans frequently indoors for this purpose.
In normal houses
you don’t get some of these issues and temperatures can be moderated much more
easily by simply opening windows. I have found that low night temperatures have
caused almost my entire Paphiopedilum and Phalaenopsis collection to spike.
The humidity indoors
is often very low. It is at its lowest in spring, when we have cool sunny days
and yet the room is warm and sunny. With A/C the situation is even worse with
dry outside air to start with, and it doesn't get any better once it's indoors.
I have found that trying to compensate for low humidity is almost useless and
obviously it’s no use against A/C. I find humidifiers completely ineffective
even indoors in houses without A/C raising it by only 5% in a medium sized room.
However, the low humidity causes only relatively minor problems such as shorter
than normal flower spikes on some plants, and may cause some ruffling of flowers
on certain plants. It probably also causes generally smaller flowers. Shrivelled
back bulbs are common on my plants, this is not a problem.
More water has
to be given to compensate for the low humidity and I have grown Vandas in baskets
with Sphagnum moss! Usually, after a 15 minute dunking in this environment they
are bone dry the next day. Without the moss, they are bone dry in 3 hours! In
most environments this moss would cause rot. Without A/C they are grown in bark
chips of CHC chips and do not dry nearly as quickly. Being adaptable to your
conditions is paramount.
Sophrolaeliocattleyas
(Slc.) in particular are difficult, and for that reason I don't really recommend
them to indoor growers, unless you are lucky enough to have good light and good
humidity with good air movement and cool nights. I don't seem to have the same
problem with Potinaras, it seems that the addition of the Brassavola (now Ryncholaelia)
genes ameliorate the need for humidity. Typically B. digbyana grows in hotter
and more arid climates than other Cattleya types, so this does seem to reinforce
the adaptability of these plants to lower humidity.
Watering correctly
is a learning process. There is no specific frequency that can be stated since
the environment governs how often you need to water.
What I mean about
environment is light, humidity, temperature and air movement - these all drastically
affect how often the plant dries out. The more light/temperature/air movement,
the faster the plant will dry. The more humidity is the opposite, with high
humidity the plant will not dry so quickly.
However, you can
learn when the plants need water. Lift the pot, it should feel light. A sharpened
pencil or flower stake inserted into the compost should come out dry, or nearly
dry. If not, don't water. If it is ready for watering, really dump loads of
water through the pot. I typically water with a quart of water per orchid, two
quarts for a larger pot. Remember that a 6" pot might have 6x
the volume of a 3" pot (not 2x) so make sure that when you do water, water
heavily with the correct volume. Heavy watering ensures that all the roots get
wet, and also any salts in the pot are washed out.
Don't ever let
an orchid stand in water, this can rot the roots. Be careful of plants placed
into decorative planters for display, these can hold water in the bottom and
almost certainly will cause less drying of the pot so a small adjustment to
watering schedules is often required.
There is lots of
anecdotal evidence that seems to indicate that one feed brand is better than
another. I for one don't believe there is much difference, if any, in growth
rates, but look for a complete fertilizer, one with all 7 minor or trace elements.
What is FAR MORE IMPORTANT is to feed correctly. Little and often, weakly, weekly
are good watchwords. Note that a 20-20-20 feed compared to a 5-5-5 feed is 4x
as concentrated, all other things being equal. This usually means it is 4x
better value! I do find that most beginners
are told to feed at low rates and this is a great way to start. I would recommend
that you feed weakly, weekly for at least the first year of orchid growing.
This will usually mean 1/4 tsp per gallon for most feed brands at every other
watering, and every fourth watering in winter.
However, it has
to be said that most commercial vendors and more proficient growers feed much
more heavily than that. However, it also has to be said that these growers have
state of the art facilities, with optimum temperature and light levels for each
genera and loads of air movement and Reverse Osmosis (i.e. pure) water so they
can feed at higher rates without burning the roots. The further away you are
from this ideal environment, and the less experienced you are, the less you
can push the plants with feed safely. There comes a point where the growth won't
be any faster because you've burnt the roots and then the plant may die.
A great deal depends
on the water quality. For example, in Seattle the water had a very low salt
content (Total Dissolved Salts or TDS). Typically 40 parts per million (ppm)
out the tap - this is lower than most bottled spring water! Back in the UK and
further south in the US you may well find TDS levels of up to 500 ppm.
Typically a maximum feed rate would be 1000 ppm alternating
with plain water. What this all meant is that one could feed at 2x the feed
rates of someone with poor water quality without burning the roots, i.e. you
could add 960ppm of feed to this water to make a total TDS of 1000ppm, whereas
a poor water quality grower may only be able to add 500ppm of feed. Half
as much. Also, when you flush the pots every so often with pure water
you'd get almost exactly that, pure water going through the pot. The poor water
quality grower will have their tap water with lots of salts in it, so won't
be able to achieve the same flushing effect with their 500ppm water. Water quality
is very important but if you start feeding with a weak concentration of feed
and flush well, you should be fine. Here in the
I do also believe
in using a couple of different feed formulations on a rotation basis just to
make sure the plants get all the trace elements they require (and a balanced
diet just in case). Current thinking is that bloom boosters (BB) do not actually
increase flower size when applied to plants in spike - these BBs
will increase the production of roots which might lead to better blooms later.
I use BB to encourage roots in the spring, and to avoid the plants getting too
lush and soft growth during the year. Note however that my opinion is that if
you don't feed with enough nitrogen when plants are in spike, the spikes will
be short. However, excessive nitrogen is known to wash out colours on Vandas.
Many people claim that using high nitrogen feeds on Vandas will prevent them
from spiking initially. I feel there is probably some truth in this, based on
my experience.
Vitamin B1 additives
do seem to encourage rooting and I do use them occasionally. Do not use
too frequently, several people have reported these causing flower distortion
if applied too often or in big doses and I have seen this on my plants when
I've overdosed the water. The result was some flower crippling and strange features
in the flowers. These were not present in subsequent flowerings.
Some people also
report vast differences when switching from one feed brand to another, this
probably means that they weren't feeding at the correct dose with their previous
feeds, although some feeds may be somewhat more suited to certain potting mixes
and water qualities and pH than others. For example it has been noted that with
pure bark mixes and urea feeds, growth is poor but adding 20% peat to the mix
corrects this problem. Alternatively use a feed with low urea (actually you
want more nitrate and ammoniacal nitrogen) with pure
bark potting mix.
I use 1/3 bark,
1/3 coarse Perlite and 1/3 charcoal for Cattleya types. Works for me. For Phalaenopsis and Stanhopeas I've used Sphagnum
moss, and also the normal mix above. The Vandas are basket mounted with bark
chunks. For the Paphiopedilums I use coconut husks, Perlite and charcoal. I
don't recommend Sphagnum moss for long term Cattleya potting since eventually
it will hold too much water (when it packs down), although initially it can
work very well to promote roots.
This may sound
like a strong statement but I never have any pests, certainly not for long since
on one or two occasions I have received pests with plants from vendors but immediate
action solved the problems. I think this is due to a combination of only buying
strong plants, quarantine for new plants, frequent inspection and good air movement
(in the case of growing indoors with A/C the air exchange simple eliminates
ANY fungal problems, this is possibly the second actual bonus of A/C).
If you have a diseased
or pest ridden plant it is often best to discard it, rather than risk infection
or expend a disproportionate amount of time nursing one plant back to health.
The selection of
plants in the
There are also
mericlones that don't perform as well as they should, these have been weeded
out along the way. This comes from mass mericloning (where thousands of plants
are produced from a single protocorm), or mericloning another mericlone or from
the incorrect use of hormones in the process. This results
in plants that either don't grow, don't flower, or the flowers are significantly
smaller than they should be. I know of some growers who limit their purchases
to divisions to avoid the problem. Thankfully the problem is not that widespread,
so you're fairly safe with a humble mericlone. However, it does occur and this
is one reason, for example, why stem propagations and divisions are more expensive.
It is worth asking the vendor how many protocorms or plants were obtained from
the cloning process, a good number would be around 250 plants, many more than
that can be problematic. You do also occasionally come across a mislabelled
plant, usually from the Far East and the language difficulty
can exacerbate the problem, along with growers using shortened clonal names.
I.e. Blc. Chia Lin 'Golden
Super' FCC/OSROC might appear as Blc. Chia Lin 'GS' with or without the award. It is good practice
to add the award to help with identification, although some plants can have
so many from the different World wide Orchid Societies you need a large label!
Cattleyas
Paphiopedilums
Phalaenopsis
Vandas
Stanhopeas
Copyright © 2003 - 2004, Adam Taylor