From: Lester W. Poole  <lwp@l...>
Date: Tue Aug 10, 1999 7:20am
Subject: Re: orchid stem propagation


Kathy ...

I have done extensive stem propagation of phals over the
years.  Phals, like people respond differently to the same
conditions.  Some phals will seldom produce plantlets from
stem propping, merely set there for years, some will be
incredibly prolific making dozens of plantlets per node.

I use the Sigma Maintenance formula modified with 5 g BA per
liter and 14.2 g of tCA.  This is basically the formula
devised by Dr. Robert Greisbach.   It has proven successful
for me over the years.  Some protocols suggest modifying the
BA from 1 to 5 g, but we settled on the 5 g as being best.
We have tested as high as 10 g, but did not see an
improvement in numbers of plantlets produced or node
performance.

The time of year is important also with the summer months
providing the most plantlets per node ... stems taken in the
fall through early spring often expressed themselves as
flower spikes.

Temperatures are important .. cool lab temps tend to produce
higher percentages of flower spikes, and warmer temps
produce the highest percentages of plantlets.  The warmer
temps also produce higher contamination rates if your
sanitation is not up to par.

Apical dominance also plays a strong role in numbers of
plantlets produced per node.  When the plantlet leaves reach
about 1/2 inch in length we cut the apical 1/2 off ... this
speeds the proliferation process from dormant buds at the
base of the stem.  When reach your final numbers merely
separate you plantlets and allow them to reach your desired
production size before planting out.

You can also induce more plantlets to form per node by
dissecting the node with a sharp blade or razor from top to
bottom, or puncturing the node several times with a sharp
needle.  This will often result in multiple plantlets where
only one may have been produced otherwise.

The stems need to be inserted in the media at the proper
polarization, i.e., the way it grew on the plant .. bottom
down, tip up.  I cut the stems with about two inches on the
bottom and one inch length on top.  This gives me ample
working stem to trim and the different lengths make in
difficult to insert into the media upside down.  On stems we
tested inserted upside down ... none grew plantlets.

You need to transfer the stems and plantlets produced
frequently due to the problems with phenolic buildup in the
media.  This will kill your plants if left unattended, we
did in on a schedule of about every three to four weeks.

I also have a personal preference to insert the stem into
the media deep enough to barely cover the dormant eye ... I
feel I get better results from this than when the stems are
far above the media.

I also like to keep about 3/4 inch of stem below the eye, I
think the stems acts as a filter and moderator to the media
and may serve as a resevour of nutrients needed by the
initial plantlet.

We work our plants on a thirty to sixty day cycle ...
different crosses and species respond at different speeds to
culture .. some very quickly, some very slow.

Hope this helps ... LWP