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Re: rooting Rosa sericea f. pteracantha

Hi Shelly and Parker (who initiated the question),

A few of points to think about.

Shelly, you make no mention of the temperature at which you keep the
rooting medium.

I have found that paying attention to the rooting temperature to be
important with some species.
The following detail (and review) is provided for the new propagators in
the group.

In order to form roots, most plants must initiate the formation of root
initials from where the root will eventually (hopefully) develop. 
Essentially, for root  initials to form, DNA must be synthesized, cells
divide  and differentiate.  One of the basic tenants of biology (and
chemistry) is that processes go faster when the temperature increases.  Of
course there is an upper limit when dealing with biological systems.  With
some difficult to root species I would suggest increasing  the "soil"
temperature much higher for the first week or so than you normally would
keep it at.  By higher I mean 85 to 90 deg F.  You do not want to keep the
temperature that hi for very long as high "soil" temps often are
detrimental to subsequent root growth.  What you are attempting to do at
this early stage is increase the rate of development of the root initials. 
After one or two weeks slowly lower the temperature back to your preferred
temperature 70-75 deg F.

There have been many successful commercial nurseries who have used no
bottom heat and in some cases no root inducing compounds.  In general, you
speed up the rooting process with bottom heat and ric's and for commercial
success, speed and high percentages is necessary. 

The other point to think about is juvenility.  Try taking your next batch
of cuttings from the previously rooted cuttings.  I have found this to work
well with Acer (Maple) species and Rhododendrons in particular but the
principle holds for many genera.  Hartmann & Kester et.al., Plant
Propagation, Principles and Practices (5th ed) (6th is now out) has a good
discussion on this topic.

Also you could try etiolation.  It is well documented that compounds that
form in the stems of plants exposed to light are inhibitors to root
initiation.  Even difficult to near impossible Quercus (Oaks) and Fagus
(Beech) species have been successfully rooted after an etiolation
treatment.

Briefly....keep a shoot in darkness when it first emerges so that it is
white (like the potato tubers sprouting under the sink).   You could
accomplish this by mounding the rose with sawdust (4-6 inches deep) early
in the spring just as the buds swell.   With other plants, try a box or a
tube  covered with foil to keep the temperature from getting to high. When
the shoot has reached  4-6 inches in length, take black electrical tape of
other opaque material and cover the lower part of the stem.   Allow it to
green up in the light.  After it has had a few weeks (3-5?) to store some
carbohydrates (necessary food for root formation) remove the stem below the
tape and remove the tape.  Treat the taped area as you please but in some
cases no treatment will be necessary.

Good luck.  Let me know when you have some plants to trade  :-)

Scott

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Scott Gregory Vergara		
Burley, Washington    USA
USDA Zone 8 Ave Min Temp 10-20 deg F. Record low 0/hi 104 
svergara@pacific.telebyte.com,  HORTULANUS@aol.com
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