John,I could not answer every of your question since I did not pay attention to some aspects.
Jim, sorry to hear you lost tesan .Is it the first year it is planted out? I think that is possibly because the roots are not so well developed as your other trachycarpus which were in the grounds for some time , before catching the record cold spell you got last year. Keep up with your good pioneering work.
Here I can only contribute some of the experiemental results from the Chinese growers.
Tesan were cultivated in Tianshui City Gansu Pronvince,Northwest China where the lowest temperature reached as low as -20C /-5Fin its bitterly cold winter.
and also the initial experiment by the plant researcher showed that they did fine with the temperature in Beijing which saw -19C as the author reported in his articles . In 1955, Tesan survived the record hit cold -20.6 C in Hefei City, East China. All these cultivation experiment indicated that Tesan are more cold hardy than regular T.fortunei due to their unique thick and stiff leaves and thicker hair protecting
the plant.
I saw the German guy sowed tesan directly in the ground and he later told me they survived -15C with only mulch whereas Winsan did not do the same good job. The following are his growing experiences with Tesan and Winsan he sent me in his email.
http://www.exotenwiese.de/53543/57793.html
"These winsan trachys do very well in a pot…they are very strong and I would never believe, that they are just very young…in the garden soil, they develop also good, but not that fast…that’s normal…I still cant tell about the round closed leafs, but they are the fastest growing trachys,."
"Tesan is growing more compact, slower and got no damage from cold and long winter…so it looks like there is a choice for a man with patience getting a cold hardy palm with a tesan or someone without patience, he gets a winsan, that isn’t that cold hardy…"
From another German grower, comes some more experiences.
http://www.exotengarten-odenwald.de/40144.html
Google translation
"after the "Killer Night" at 05 Januar 09 mit Temperaturen von unter -21° und Temperaturen von -18° bis -20° in den folgenden Nächten sind die Blätter aller ausgepflanzten Trachys erfroren, egal ob mit oder ohne Schutz. January 2009, with temperatures below -21 ° and temperatures of -18 ° to -20 ° in the following nights, the leaves are all planted Trachys frozen, whether with or without notice. Die Pflanzen haben sich aber alle 2009 wieder gut erholt und den Blattverlust fast ausgeglichen. The plants have all but recovered well in 2009 and the balance sheet loss fast. "
Anyhow, Withe regard to the hardiness,that is a complicated question since the health and age of the palms ,cold duration and humidity are all involved . There is much variation of Trachycaprus species in term of leaf, hair and hardiness.
I believe the hardiness gene exist in trachycarpus and we need to find them out With patient and specific selection and breeding, we could cultivate a good variety with nice appearance and better cold hardiness.
That is why we heard there are dozens of other trachycaprus species which are supposed to be very cold hardy as well. Tesan is just one of them. The odd thing is I recently read on EPS that Nova survived -16C iin the previous year ,followed by -19C last year in Holland. This is against our normal view about this bit of slender trachycarpus which may not be as cold hardy as T.fortunei.
