Date: Sat, 1 May 1999 23:53:34 EDT From: CMDodd@aol.com To: cp@opus.hpl.hp.com Message-Id: <aabcdefg1510$foo@default> Subject: Nepenthes propagation and breeding
Dear Nepenthophiles,
Thank you for the kind comments, just trying to help!
Part three: Now you have some (or maybe even too many) Nepenthes and
they are growing like weeds. Or perhaps a friend has a plant you like and
can spare a piece. Or suddenly several plants come into flower. What to do,
what to do?
Just a note: This makes little mention of tissue culture, as this is
outside my experience. This may be the 'salvation' of many species and I
can't say enough good things about it, but this is primarily about low-tech,
at home propagation.
Propagation of Nepenthes can be easy or difficult and sometimes
frustrating. It all depends on what you have to work with. In the early days
of the hobby it was often unusual to find rooted plants for sale. When you
did it was often impossible to be sure that the plant you bought was actually
the species or hybrid represented by the seller. Now I don't think much of
this was dishonesty on the part of the seller, rather, it was mostly
ignorance due to a lack of information available. But when you did find a
plant and could positively i.d. it you could always take a cutting. A
cutting is a non-technical way to make a clone, a genetic copy of the donor
plant. This is not always as simple as it sounds, there are several ways to
arrive at making one plant into two or more.
One method that I saw more than one person try without much success was
air-layering. If you wanted to airlayer a Loquat tree that produced
especially good fruit you would find a small branch and make to incisions
completely around the stem about two inches apart and then make a slit
between the two and remove the cylindrical outer layer of tissue. This
allows water from the plants roots to keep the branch alive but prevents
nutrients from going past the cut downward. Its been a while since botany
class but I think the xylem which carries the water is down deeper than the
phloem that carries the nutrients which is removed in the process. It may be
the build up of trapped nutrients in the branch forces rooting, but I am not
sure. The wound is wrapped with sphagnum and covered with a plastic cover and
tied. Eventually roots form where the wound is, fill the sphagnum and then
the branch can be cut and planted as a seperate plant.
Vines however are a different matter. I am uncertain about Nepenthes but
in many vines the xylem and phloem are arranged in bundles throughout the
stem rather like a monocot (i.e. a palm or grass). This protects a climbing
plant from total damage and stem death as it is bent, kinked or banged about
along the host plant during wind or falling limbs. Therefore I think what is
happening in Nepenthes is that you cannot completely cut off the phloem and
initiate root development.
Simple cuttings are general propagating material but there are a few things
to consider. There are two basic types tip and lateral. Tip are mearly the
very ends of the growing plant. Since they are soft new growth it is best to
leave 3-5 leaves on this type. Lateral cuttings are any cuttings that are
not tip cuttings, i.e. cuttings lower on the stem. New growth points or
nodes, are above each leaf, the portion between them are the internodes. How
many nodes per cutting is a mater of choice. I generally use two, sometimes
three, but I know of people successful with single node cuttings. Tip
cuttings will give you a much better looking plant more quickly, but alas you
only get one per stem.
Leaves. To shorten or not to shorten, that is the question? I think it
depends on humidity. If you are rooting under mist or in plastic bags it is
unnecessary, if you are merely rooting out in the open in a greenhouse it is
a good idea to reduce the leaf length by 1/3. Why? A plant is nothing more
than a biological pump. Water enters at the root, travels through the stem
to the leaves where it evaporates out through stomata. A cutting has water
leaving it but no roots to supply water (though some is absorbed by the cut
end). The amount of leaf area cannot be so great the leaf desicates.
Reducing in will help. Leaving pitchers on the cuttings and keeping them
full of water may also help, the cuttings absorbing water through the
pitchers.
Once you have taken a cutting there are a few ways to root is. For a
while I used the inverted pot method (see Bailey's Cycopedia of Horticulture)
but this was not very efficient. Cuttings often root in live sphagnum, or
rock wool. One method used at Atlanta Botanic Garden is to put the cuttings
directly into the final growing media and then place the pot in a clear
plastic bag, placed in bright indirect light (to prevent that 'boil in bag'
cooking effect from full sun) and check on them from time to time until new
growth begins. I often take a cutting, place it in a small pot of sphagnum,
place it in the relative shade and humidity of the floor of the greenhouse
and treat it as all the other plants in regards to watering.
Success with cuttings depends on the age of the material. The lower you
go on a stem, the less likely you are to get it to root. Hormones can be
used. ABG uses Dip-n-Grow and I have used it as well, but I have found that
if the material you start with is healthy it is probably not necessary.
Bottom heat can be used in cool weather, here I usually wait until mid spring
for lowland plants and fall or early spring for highland species.
Cuttings of plants taking in the upper pitchered climbing stage usually
remain in that stage until the new plant breaks a basal.
Grafting is something I only attempted once and with only a 1 in 4
success rate with 4 plants. I am simply not good at grafting, but I do plan
to try it again in the future. I think it is useful to grow plants that live
on exotic substrates like N. rajah or northiana onto a vigorous root system
of say N. x mixta.
Often I am reluctant to take any cutting from a plant with a single stem
unless it is very common or has started the production of a basal rosette.
Here is an interesting observation made by Ron Determann of ABG and very
useful. If you take a climbing stem of a Nepenthes and pull it down below
the media level of your container (easy if the plant is hanging high in the
greenhouse) the plant often will soon thereafter start a basal shoot. We
believe this has to do with hormones and gravity and their transportation
within the plant.
Now a word about sex. (No, in plants.)
Seed production in Nepenthes is not difficult, raising seedlings is
however another matter. Nepenthes of course have seperate sexes. On major
problem in obtaining seed is getting males and females together (rather like
humans). A great help in getting simultaneous flowering is to place all
plants of one species next to each other in a greenhouse situation. This
means that they will share a common microclimate (i.e. similar lighting,
humidity, etc.) Pollen from the male is most easily applied to the female by
cutting off an individual male flower being careful not to shake loose the
pollen and then daubing it on the stigma of the female flowers. Candlelight
and soft music optional.
Anyway, after a few weeks the seed pods should start to swell and
eventually they will turn brown before opening. It is a good idea to place a
stocking over the female raceme to catch the seeds. I have had more than one
seedling volunteer in a pot that I was later unsure of the parentage. For
best result sow as soon as possible.
Hybridizing can really be fun in Nepenthes but let me give my opinion of
the ethics. If you have the oportunity to create species seed or produce a
hybrid, first create the species seed, unless you are dealing with a very
common plant like N. ventricosa which everyone including your grandmother
has. Some of these plants are in trouble in the wild and even if not, it may
only be harder to get imported plants in the future. If you produce species
seed and grow them on you will also end up with species plants better adapted
to cultivation as those will select out. All this aside, you may not have
both sexes of a species in flower or you have the opportunity to create
something that has never existed before, by all means give hybriding a try.
We today are very fortunate in having a widest range of species in history to
work with. We may learn about genetic barriers by cross-breeding, produce
more easily culivated plants through hybrid-vigor or just have fun.
Personally I like to see what are called F1 crosses, that is one wild species
hybridized with another. I have made more complex crosses but there comes a
point when very complex crosses all start looking alike. Also the further
from an F1 cross the poorer the seed set, germination and survival rate I
have experienced.
The thing I have the most trouble with in Nepenthes is going from a
germinated seed to a silver-dollar sized plant. After that its usually all
down hill. I have germinated literally thousands of N. lowii, truncata,
bicalcarata, both imported seed and seed produced here and ended up with as
few as one or no adult plants after two years. Fungi is probably a major
cause, as is the ease of drying in such thin tissue. I would love to hear
from anyone who has regular success with the seedling stage. I have tried
many different medias, sterilized the soil, sown atop used media, etc., but
this is the toughest stage of their live cycle. This is where tissue-culture
really comes in. If you produce interesting seed, by all means sow some for
yourself, and then send some to a lab for culture. Work out a deal with the
lab for your cost and/or sales of the plant but this is the best was to
insure something will survive your efforts.
Lastly, if you have extra cuttings or plants of rare material, my adress
is: No seriously, send them to a reputable Botanic Garden to insure their
future and to educate the public (a daunting task to be sure). Berkley,
Atlanta, Missouri, whatever, get those plants spread around so they can be
around for a long time.
I hope that this has been helpful, please forgive any erroneous
science, poor spelling, bad grammar and lousy proofreading. I have tried to
give credit where credit was due and hope no one was left out.
Good Growing,
Cliff
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