Dahlia imperialis
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
winter.
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
cultivation.

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