The Paphiopedilum
Grower’s Manual
Air
movement has a critical influence upon the health of our plants. It is a life-and-death factor, ranking
only slightly below the effects of over-watering, yet it is often overlooked
and seldom understood. It is responsible
for maintaining even temperatures and for generating humidity within the
growing area, as well as for keeping fungus and bacteria in check.
‘Good
air’ is that which is humid, but not saturated with moisture. It moves briskly, but not harshly. It has a clean, fresh smell to it, and
makes the air around us feel ‘alive’. Warm, dry air is harmful. Saturated, slow‑moving or stagnant air is equally
bad. The proper amount of air
movement is that which balances your combination of light, watering technique
and potting media, and it determines whether or not your growing conditions
will be successful.
Air
movement will allow you to regulate the amount of light you wish to grow your
orchids under. Since stronger
light intensities will also raise the temperature in your growing area, it is
necessary to ensure that your plants do not get too hot under such conditions. Of course, adding more shade will help,
but it may not be necessary when the addition of a fan, or the opening of a
window is all that is needed.
Your
watering technique can also play a part if you increase your light conditions,
since the evaporation of water will also lower the temperature in the growing
space. Good air will allow you to
water your plants frequently, and to enjoy the magnificent growths of your
plants from its effects. There is
a balance to be maintained between these elements, and you can decide for
yourself just how it might be accomplished.
Good
air is that which takes excess moisture out of the pots and suspends it in the
atmosphere as humidity, and in so doing it serves to lower the surrounding
temperatures. In areas of
high natural humidity this happens more slowly than in drier climates and with
less fluctuations in temperatures.
Proper air movement is not easy to describe; it must be experienced, and
there is no formula for maintaining good air, since every growing situation is
different. Once you learn how to
judge what is needed in your particular environment, you will then be able to
take measures to provide those needs.
In
order to get the feel of what good air is really like, take a look
outside. Any time of day will
do. Is there a time during which
all movement stops, and not even a leaf quivers? Momentarily perhaps, but not often. Outside we may see leaves fluttering,
branches swaying, or at times, even trees bending. If the movement is slow, only the leaves rustle, but with
increased air movement the grasses will bend and fallen leaves will fly
about. This is easy to detect, but
how about the gentle breezes which can barely be noticed. Certainly they are pushing air, but
just how much is moving?
Have
you any idea of the volume of air that moves past you while you stand
outside? If you can find someone
who smokes, have her puff some smoke into the air while you study the direction
in which it moves. Also, notice how
rapidly it dissipates. If you were
to enter your home growing area and make the same test, what would be the
results? Chances are, that the
smoke would linger for some time before it dissipated. Could you in fact, feel any air
movement on your face?
When
air movement is restricted the air becomes layered. Warm air moves upward and cold air falls. Inside an enclosure such as a home,
this can provide false information about the conditions affecting the
plants. A thermometer placed at
eye level might be far different from one at plant level. In order to prevent the air from
stagnating in layers, it is necessary to keep it moving sufficiently enough to
thoroughly mix the warm with the cool.
When
the heater goes on, the heated air rises to the upper confines of the room, and
then it slowly drops horizontally as it warms more and more of the cool
air. For tall plants, this might
mean that their roots could be too cold while their tops are too hot.
A
plant needs even temperatures about it rather than having it attempt to
continually adjust its growth to constant changes in temperature. At night you should not feel cold feet
while the rest of your body is warm.
Even temperatures are necessary for proper growth.
As
with the heating system, the greenhouse cooling system also needs to have its
cooled air circulated efficiently.
Generally, there can be somewhat more fluctuation between the
temperatures at your head and those at your feet during the daytime than would
be acceptable at night, mainly because of the different states of metabolism
which the plants are in during daytime and nighttime. Nonetheless, this cooled air should be evenly distributed as
it moves over the plants. Cooled
air coming directly from an evaporative cooler should be deflected before it
reaches your plants unless you have arranged them within temperature ranges,
from ‘cool’ nearest the cooler, to ‘warm’ at the other
end of the enclosure.
Self-contained
cooling units have a powerful fan that blows cooled air into the greenhouse,
but if no other fans are installed for its distribution, there can be a marked
layering of air inside. It is a
good idea to install several small fans at the eave-level, blowing directly
toward your plants to generate a pattern of airflow that circulates around the
greenhouse interior. The same
direction of circulation should be maintained for both the heater and the
cooler, and each of these units will then increase the flow of air.
Fans
blowing directly upon your plants will prove beneficial, and in combination
with a more open potting mix, it will allow you to maintain a more frequent
watering schedule, as well as providing the benefits of more humidity. If you find your plants do not respond
favorably under those conditions, they are not receiving sufficient water.
As
soon as plants are watered they begin to dry out. Without air circulation this evaporated moisture saturates
the air, and it remains in the immediate vicinity of the plant, preventing
further evaporation. This can lead
to the rotting of the root system unless steps are taken to remove it. Even the slightest breeze will do this
outside since such large volumes of air are moved. But inside most homes it is a different matter, for without
the use of a fan there is insufficient airflow to move the air, even beyond the
next plant.
Just
after the plants are watered, that circulating air needs to remove the
saturated air from the immediate vicinity of the plant, and to disperse it
elsewhere within the confines of the home. As long as there is moisture inside the pots, it will need
to be continually removed in order to maintain a balance of humidity within the
surrounding air, as well as to provide air for the roots of the plant.
Except
for those growers living in warmer climates, which frequently have a high
ambient humidity, most all orchid growers are faced with the problem of trying
to maintain sufficient humidity.
Fortunately, as a result of these increased volumes of circulating air,
we can then realize a substantial increase in humidity within our enclosed
spaces.
Many
elaborate mechanical or electro‑mechanical systems have been devised and
installed in an attempt to fulfill this need, but none seem to be without its
problems, and trying to keep them clean and free from lime-scale seems a never‑ending
chore. The cost to install and
maintain these systems is no small matter, either. So why bother with them, when a simple installation of more
fans will actually be better for our plants?
If
you have ever wondered why just a few plants will not grow well in a nearly
empty enclosure (your home), it is itself, the reason why. Remember, that the reason we try to
maintain a high level of humidity is because when humidity is up, they can
absorb the moisture from the air.
Conversely, when the humidity is lacking, they will become desiccated
and grow poorly. A well‑balanced
growing space is a full growing space, for each plant as it dries out, provides
moisture for the next.
For
each molecule of water that evaporates, a certain amount of heat is given
off. This reality can be put to good
use by simply making adjustments in the amount of air circulation within the
growing area. Yet, while this cooling effect of further increasing air movement
is beneficial during warm days, it is not useful during cold nights, since we
do not want the cooling effect from evaporation. On the other hand, it may be a useful tool during hot summer
nights to lower elevated temperatures.
In
hot, dry climates, evaporative cooling is an efficient and economical method of
keeping the home cool. When there
are days of high heat and high humidity, the output of the cooler will
be greatly diminished, and as a result, temperatures can remain too high in the
home growing area. Misting is
frequently required and suggested in this situation, as a method of further lowering
the temperature. Misting works
well even when humidity is high, because it provides countless additional tiny
molecules of water that can be evaporated, thereby absorbing more heat in the
process.
It
is important to maintain good air circulation, for it is also an essential
method to fight fungus and bacteria by keeping the plants dry during the cooler
temperatures of the nighttime.
Also be aware, that during freezing temperatures, particularly at night,
moisture is drawn both from the atmosphere as well as from the plants’
tissues, and it collects as frost on the inside glass of the windowsill.
Wetting down the walks will provide an extra source of moisture for this
evaporation. For plants placed on
a gravel-filled tray, with water nearly covering their surfaces, it can provide
an additional source for this evaporation.
In
areas with high ambient humidity, evaporative cooling is much less effective,
but it still can be utilized. In
order to compensate for the difference in rates of evaporation (cooling), an
adjustment can be made to your watering schedule. The idea being, that since a given volume of air is able to
evaporate a given volume of water, it is better that the evaporation take place
within the cooler, rather than sucking moisture from your plants.
A
combination of increased airflow and a carefully regulated watering schedule is
very effective, since it can still provide your plants with their needed
humidity and it will not aggravate the problem of excessive moisture.
If
there are other sources of water available for evaporation, such as plants
under the bench or loose gravel walkways, water will be evaporated from them at
the same rate as from the potted paphiopedilums. In dry climates these sources of extra humidity are
essential, but are less so in areas with high ambient humidity.
You
should try to regulate your irrigations according to the moisture requirement
of the plant. It may require a bit
of experimenting for you to judge the timing for this, but some orchid leaves
and/or their pseudobulbs will often become flaccid, or almost limp (in some
orchids like certain paphiopedilums) when they become desiccated. Healthy orchid leaves are turgid and
firm to the touch, and when they are limp, they need more moisture.
In
the tropics, many weeks or even several months may elapse between watering; and
in fact, most orchid collections are housed outside, under protection from
rainfall. The ambient humidity in
the areas is enough to supply the moisture needs of the plants for long
periods. But inside an enclosed
area like a home, the movement of air is not the same as outside, so it is not
a good idea to maintain humidity too high (yes, that is possible)
because of the increased likelihood of bacterial or fungal infection.
Remember,
plants need to be able to quickly dry off, so provide them with this capability
when they are restricted to the confines of an enclosed growing space.
Orchids
need light. In cultivation,
sunlight produces stronger and healthier growths. Although orchids are seldom found growing in direct sun in
habitat, there are numerous individual plants of many species, which can be
found growing in the direct sunlight.
Whether the overgrowth had recently been removed, or the seed had
actually germinated in place may not be known, but those particular plants
seldom exhibit signs of extreme stress.
If all the necessary requirements for seed germination and seedling
growth are met (with the exception of light), it will be found that the
heaviest populations of plants will be found growing in the brighter places.
Each
species has its own light requirement. Most species will be found either on
east-facing or on west‑facing slopes or trees. Some will be found on south‑facing slopes in the
northern hemisphere, while others grow on north‑facing slopes in the
southern hemisphere. These areas
provide bright light conditions, while protecting them from the intense midday
sunlight.
In
some habitats, particular light requirements are so critical that many species
limit their range only to those slopes receiving the intensities that suit
their particular needs. Even in an
area populated over a range of several square kilometers by a species, it will
not be found growing away from its optimum light source. Searching hills and gullies at
distances of only a hundred feet or less, away from a colony of plants, will
verify this fact.
When
placed in an artificial habitat, orchids will grow in a wide spectrum of light
sources; from deep shade to full sun, they will still prosper. Perhaps the most beautiful and
succulent plants are those grown in more shade, as the markings on the leaves
of the mottled-leaf paphiopedilums glisten with a crystalline radiance. The greens and blues are deep, the
silver is bright and growth becomes luxuriant and full. Flower stems elongate and the flower
colors deepen, for those that will bloom under such shade. Everything appears so beautiful and
perfect. In fact, there is nothing
wrong with deeper-shade culture, and it can be maintained if flower production
is of little importance.
Problems
arise when a plant grown in such a way is then transferred to a brighter
location, as it can easily become sunburned. Or if there is a sudden change in temperature, especially a
lowering of 10° to 15°, these ‘soft’ plants become
susceptible to diseases much more readily than those ‘hard’ plants
grown in more light. Also, growths
and leaves of these plants can be easily broken off, even by a light touch.
Without
sufficient light flowers may not be produced, or at least their production will
be considerably lessened, and this usually is not compensated for by the
appearance of those deeper colors, showy foliage and longer stem lengths. One idea is however, to grow the plants
in brighter light and then transfer them to more shade when the flower sheath
is first noticed in the new growth.
In such a situation, the deeper flower colors can still be realized.
Orchids
which are grown in very bright light, anywhere between 5,000 to 7,500
foot-candles, which is more than that recommended for mature Cattleya orchids, will produce a large number of
flowers. Plants in such conditions
grow very compactly, they are more yellowish, and those paphiopedilums with
mottled leaves show few of the crystalline cells. Their mottling in fact becomes rather different and
sometimes they do not even look like the same species as when they are grown in
more shade. All these orchids have
tough, leathery leaves and hard pseudobulbs, and have much shortened flower
spikes. The flowers lose their
colors soon after opening, but they remain on the plant for a longer period.
More
growths are produced under these brighter light intensities, and flower production
can be truly amazing. Many species
which seemed reluctant to bloom will do so profusely when grown under higher
light conditions. They also bloom
more often since they will produce more mature growths each year, and they can
produce more flowers per stem.
Resistance to many diseases is another benefit of this culture; and the
plants can be moved about with little danger of becoming sunburned, catching a
chill or from mechanical damage.
Unfortunately,
too much light makes for a less attractive plant, so you will want to
consider the optimum light for your own collection.
Until
just a few years ago, most orchid species were grown under rather shady
conditions, since literature said it is the way it should be done. Exploratory
trips to the habitats of many of these species, combined with experiences of
other collectors, have verified the benefits of growing orchid species in much
brighter light conditions than growers had ever done before.
But
if nearly all species of cultivated orchids are grown in too little light, just
what is the optimum? It is a
question for each grower to decide for himself, since there are several
choices. If beautiful foliage is
more important than flower production, then the answer is for less light. If flowers are more important, then it
will have to be more foot-candles.
Anything in between is acceptable and preferable, since we want to
maintain a balance between good‑looking plants, and healthy plants which
produce many flowers. Besides,
there is not a whole lot that can be done to dramatically increase the light
source in most homes.
Generally
speaking, most orchids grow best under the same conditions as those recommended
for Cattleya
orchids. There are certain species
which do best under lower light conditions, such as those recommended for Phalaenopsis orchids, and there are some that prefer
brighter light intensities as do Vanda orchids.
Each
grower should be ready to test his plants to see where they do their best, and
then grow them accordingly. This
process may take several seasons before it is known just how much or how little
light a certain species needs in order to flower well, while still maintaining
an attractive appearance.
Do
not hesitate to move your plants about to find these optimum conditions. Do be sure to give a plant a year or
two in its spot, so that you can make a valid judgment. If you have divisions of the same
plant, you can try each piece in a different location in order to find the
correct answer.
Do
not be overly concerned about the ‘proper’ amount of light you
should provide, and if in doubt, just give them the best you can. You can always make changes if
necessary.