Re: Nepenthes: temperature and air circulation

Date: Fri Apr 30 1999 - 19:57:34 PDT

Date: Fri, 30 Apr 1999 22:57:34 EDT
Message-Id: <aabcdefg1502$foo@default>
Subject: Re: Nepenthes: temperature and air circulation

Dear Nepenthophiles,

     Here is round two on the early trials and tribulations of Nepenthes
cultivation, this time on two more often misunderstood parameters: tempature
and air circulation.

     In my early days, just getting into the growing of Nepenthes, not many
different species were available. As priviously stated, I started with N.
sanguinea, which was not the best species for Florida. Later I found an
unlabeled species in a nursery outside of Honolulu which turned out to be N.
mirabilis. The next plants to show up were four specimens of N. rafflesiana
from Jerry Horne's Nursery in Miami. I thought these were the coolest things
I had ever seen! They were nicely grown and all had those marvelous
pitchers. On the way back to Daytona I ran my car off the highway in a
rainstorm (hydro-planing) and it was nearly the end of me and the plants!
Next several cuttings were offered and purchased quite reasonably from Joe
Mazrimas of CPN fame and at least some of each of the varieties rooted. I
was on my way.

     Most of the plants did very well, not because I really knew what I was
doing, but because Florida is not unlike Malaysia for much of the year: hot,
humid, frequent rain, intense sun. My first greenhouse was an awful mess. I
think it was 8 x 8 x12 and the lower four feet of the house was 4 x 8
pressure treated plywood, only the top half letting in light! It was rather
dark, very hot as there were no fans or cooling, with sides that opened to
let in air (and pests) yet the plants did fair. Disease was a problem
however. In the stagnant air fungi proliferated. In winter I heated with
kerosene (yipe!) and on one cold morning near freezing was greeted with a
rather cold greenhouse filled with choking black smoke. Not a good day.

    Anyway, up until then all of the plants, both species and hybrid, were
all lowland plants. Plants from sea-level to about 4000' elevation can be
considered as such. It wasn't until I brought in some N. fusca that the
importance of temperature begin to be fully appreciated. Imported in October
the plants were potted up like all the other species and put into the
greenhouse were they began growing and pitchering. No problem! Until
summer. The plants began to go into decline, stop pitchering and look ratty,
until about November when they begin to recover a bit. Hummm? It was
obvious that the plants disliked Florida's high heat summers when the
greenhouse might reach 100 degrees F. on a sunny day. So the plants were
placed in a 30 gallon terrarium under lights, in front of a small window A/C
and kept at a near constant 68 degrees. Now they nearly stopped growing
altogether and put out only a few leaves a year.

    It was about this time that again Bruce Sutton who also grew a few
orchids (Paphs. mostly) with his Nepenthes read an article in an old American
Orchid Society (AOS) bulletin. A man in his attempt to grow some very high
altitude orchids has made a lighted, negative pressure growth chamber for
some very rare species. It was a miserable failure. His emphasis was on
atmospheric pressure at high elevations, which turned out to be irrelevant to
the plants. The article then began to describe something about a parameter
he did not take into consideration: temperature cycle and a phenomenon called
mountain effect.

     Under the tropical sun even fairly high elevation areas can get quite
warm during the day. The rocks near where N. rajah grows on Kinabalu can be
warmed to nearly 100 degrees if directly exposed, though the air itself is
much cooler. Even so, in montane areas where the daytime temperatures reach
80-85 degrees, at night mountain effect takes over. The higher elevations of
a mountain cool rapidly and the cooled air sinks toward the lowlands. Warm
moist air from the lowlands is forced up the mountain by displacement and
where the two meet you get dense fog/clouds. This explaination of mountain
effect may be incomplete but the idea is that the plants are cool to warm and
maybe even on the dry side by day and cold and moist by night.

     I have been told that the reason you can't grow high-altitude plants in
the lowlands is one of physiology. The plants are making food (sugar and
starches) by day and metabolizing it by night. They are designed to do this
at lower temperatures and at high nighttime temps they slowly starve to
death. Also a secondary problem is one of pathogens. It has been suggested
that many fungi and other pests cannot handle this temperature shift as well
as can the plants and this means the highlands are relatively free of
limiting disease. I am not a scientist and my knowledge of the above is
second hand but I think this is fairly accurate, if not corrections are
welcomed. Logically it all boils down to this: If highland species could
thrive under lowland conditions they would already be growing in the
lowlands. Duh.

     From this information we designed a greenhouse for high-altitude
species. The data from elevations we tried to simulated had the daytime high
temps at 82 degrees and the nighttime lows at 52-55. With this setup and a
lowland house Bruce and I figured we could grow 95 percent of all species.
Things like N. villosa would be beyond the constraints of our system. The
design was long and thin 8 x 8 x 36', with two fans, and later nick-named
'the wind tunnel' .

     The first step was to get the daytime temperature down from Florida's 95
degree summers to 85 or so. This was done through evaporative cooling. A
pad of cool cell or other greenhouse cooling material is placed high on one
end of a greenhouse, fans and thermostat are placed at the opposite end.
Water runs through or is sprayed on the cooling pads and as it evaporates you
get cooling! Cool, huh? In addition a humidifier was placed as the pad end
of the greenhouse and as mist was pulled through and evaporated along the way
additional cooling was generated. Further placement of the greenhouse was
such that it received no direct afternoon sun by shading it with a deciduous
tree (mimosa). The results were the greenhouse did stay around 82-85 for all
but the hottest heat waves. When you consider how poorly evaporative cooling
works in a high humidity environment (insert "Florida" here), imagine how it
would do in a dry climate!

     Nighttime cooling had to be more direct as evaporative cooling could not
bring our nightime lows of 75 down to 55. Here a GE Zoneline A/C was used.
In my business we had many used ones and a 15,000 btu unit was chosen to cool
an area of 8 x 8 x 24' to 55 degrees plus through partitioning an area of 8 x
8 x 12' to 65 degrees (this was for cultivation of mid-elevation species like
N. ventricosa and some of the sanguinea). This proved very sucessful, if a
bit expensive, and allowed cultivation (and growth/pitchering!) of highland
plants like N. lowii and burbidgea at sea level. Note, I believe simulating
the temperature cycle of highland plants is a must for their sucessful
cultivation, it is NOT an option. Couple this with correct media and high
quality water (VERY important for highland species!!) and they are no more
difficult than lowland plants with few exceptions. One word of warning, A/C
type cooling removes humidity from the air and must be run in conjunction
with some form of humidification.

     Air circulation is more straight-forward. Very few of these plants live
in the wild in stagnant air. Maybe N. ampullaria in some peat swamp would be
an exception, but many are road-side plants of disturbed habitats, colonizers
of landslide areas, mountain ridgetop growers, etc. In short they have good
air movement around them. This prevents disease spores from colonizing the
and keeps water from sitting on the plants for long periods. Fans, both
exaust and simply air circulating fans inside a greenhouse will keep the air
moving. In terraria a small aquarium pump coupled with an airstone placed in
a jar of water will exchange air and humidify all at once.

     As a heads up Atlanta Botanic Gardens (ABG) is in process of starting a
highland house to be finished by 2002, I think. They will be using somewhat
different technology for cooling and they will have a premiere display when
completed. It will showcase three distinct highland areas, two of special
interest to CPers, Malaysia (Kinabalu), the Tepuis, and the Andes.

    Next time a bit on propagation and breeding.



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