Cosmos atrosanguineus

Rodger Whitlock
Sun, 16 Sep 2012 12:38:18 PDT
On 16 Sep 2012, at 9:25, James Waddick wrote:

>  I am sure regular readers of this forum and of the wiki are 
> aware of the odd history of this tuberous species. See 
>  The plant was originally collected in Mexico, then believed 
> to have become extinct. All cultivated plants are a single clone 
> propagated by micro-propagation or division of its Dahlia-like 
> tubers. The plant is sterile and produces no seed.

It appears almost certain that more than one clone has been in cultivation, 
contrary to the received truth. New commercial clones have been coming out of 
NZ, Japan, and possibly the Netherlands. I have one, 'Chocamocha', distributed 
in Canada (and, I suppose, the US) by the Proven Winners people.

This development, it seems to me, would not have come about had only one clone 
been in cultivation. A possible wrinkle is that within the last few years, the 
plant has been rediscovered in the wild, in Jalisco, Mexico, and seed gathered. 
My understanding is that that seed went to the Rancho Santa Ana Botanic Garden, 
but there's no telling just how widely it was thence spread.  

The archive of this mailing list has some older discussion worth reviewing.

> A few years ago a fertile  seed strain was 'discovered' in 
> New Zealand and has slowly entered cultivation.  Seedlings can be 
> crossed with the established clone to produce fertile seed and at 
> least a couple of new cultivars have been developed.

According to a member of the SRGC who kindly sent me a few seeds two years ago, 
the issue is that the plant is self-sterile and the usual commercial clone sets 
very little pollen. However, at least two SRGC members have obtained viable 
seed from their own specimens.

>  By an odd coincidence I was recently given a small quantity 
> of seed of  this still very rare plant. Of course, having never grown 
> it from seed, I'd appreciate any guidance from any of this group's 
> members who may have grown this species from seed or  some 
> suggestions on how best to succeed.

Here's what I did: Seed arrived in 2010. I held it over winter and sowed it in 
spring 2011 in a 4" square pot. Generally speaking seed of the Asteraceae, if 
sown in fall or winter, tends to simply rot. I don't remember how long it took 
for seedlings to emerge once sown, but it wasn't very long.

When the seedlings had formed true leaves and were actively growing, I potted 
them on together into a 150mm high x 115mm square pot. Later in summer 2011, 
they were again potted on into a single pot 210mm x 210mm.

In fall 2011, I put the pot into my carport (along with my pots of commercial 
clones) and allowed it to dry out. When colder weather approached, it went into 
cold, but frost-free, storage for the winter, bone dry, but the tubers still 
potted in soil. In spring 2012, once the threat of serious freezes was past 
(say, in March), the pot was brought out again into the carport, but water was 
withheld until active growth started. In this regard, the plant is similar to 
the Japanese woodlander, Pinellia cordata 'Yamazaki': no water until you start 
to see leaves emerging and even then only small amounts until you have active 
growth. Weldenia candida, another Mexican mountain plant is also best handled 
this way.

My seedlings has been potted on twice this year. They are currently in a pot 
300mm high and 280mm diameter, and are flowering to beat the band. The 
seedlings produce reasonable amounts of pollen. Applyied by hand to flowers of 
the usual commercial clone, I am getting significant amounts of seed: say, 
between ten and twenty seeds per flower. The back cross (commercial clone 
pollen on seedling flowers) is not as productive, but there is some seed 
forming from it.

Using seedling pollen on 'Chocamocha' is producing lesser amounts of seed.

It is quite clear that the chocolate cosmos enjoys plenty of root room and lots 
of water during its period of active growth in summer.

>  It is still too rare to mess up.

In my books, it is no longer a rare plant and hasn't been for a good ten or 
fifteen years since the commercial was cleaned of viruses and widely 
propagated. As the generous donor of seed to me put it, nurserymen like it 
because it usually dies and has to be replaced annually. It's sold here in 4" 
pots for about $5 a pop.

What remains rare is seed. Some of you may be tempted to write me asking for 
some, but please don't if you aren't familiar with this plant and don't have 
the time and patience to bring seedlings to flower and produce seed on your 
own. My private goal (method of attainment as yet uncertain!) is to convert 
this plant to one which is widely grown from seed by those with the necessary 
interest. Otherwise, in not too many years, we may be back to having only a 
single, sterile, virus-laden clone that challenges even the best growers to 
keep alive.

Rodger Whitlock
Victoria, British Columbia, Canada
Z. 7-8, cool Mediterranean climate

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