Dahlia imperialis

320083817243-0001@t-online.de 320083817243-0001@t-online.de
Tue, 18 Oct 2005 12:57:16 PDT
Dear All,

I have grown Dahlia imperialis for some years both in very large pots and 
planted in the open garden here in northern Germany and they grow to 
exceptionlly large foliage plants. I tried to root a tip cutting in August with 
the idea in mind to have a small manageable plant in a pot flowering in winter 
but the tip cutting did not root. I grow several different clones from 
differend provenance but all seem to be extremely short day dependent so I 
never saw a flower. 
For the winter I dig up the roots from the garden and store the potted ones in 
the cellar. However I have a feeling that this year I may not be able to lift 
the root of a giant two stemmed specimen about 4m high in one season........ 
But stem cuttings root ever so easily. And I may try with a thick mulch this 
I remember a discussion about this plant some time ago where Alberto Castillo 
mentioned a day length neutral form being cultivated in Argentina which flowers 
there in the southern hemisphere summer. I tried hard to get any further 
information on this special clone but no success and no further news from 
Alberto on this subject. A day length neutral form of this plant would be the 
perfect solution!
Does anybody of you have come across of such a form?
There are more "Tree Dahlias" than Dahlia imperialis and the earliest to flower 
seems to be D. campanulata but I lost this one, it simply did not sprout this 
spring although the pot is full of firm tubers. Others are D. excelsa which 
seems to be an uncertain species or perhaps a hybrid and often gets confused 
with D. imperialis. No flowers seen on D. excelsa either but it is much shorter 
and does not etiolate so much under glass as does D. imperialis. A very 
interesting species is the semi epiphytic "climbing" Dahlia macdougalii. It 
looks like an elder but flowers in winter with large bunches of small white 
flowers, only on VERY large specimen, though..... The last one of this group of 
Dahlias is D. tenuicaulis with dark red flowers but this does not seem to be in 

I have brought some of them into my new empty so far unheated greenhouse hoping 
to see some flowers and will keep you informed in due course (hopefully!)

Greetings from Germany, Uli

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