Tropaeolum notes
Sat, 12 Jan 2008 12:55:53 PST
On 11 Jan 08, at 15:56, Jane McGary wrote:

> I wonder if anyone has successfully propagated these plants by cutting
> the tuber (which looks like a little potato).

Many, many years ago at a one of the study weekends, Paul Christian 
held forth on the propagation of bulbs. (Memory says it was a Hardy 
Plant Study Weekend at Edmonds, Washington sometime in the mid or 
late 1980s, but don't quote me.)

One of the most interesting sub-topics was vegetative propagation of 
cyclamen; perhaps the same method would work for tuberous tropaeolums.

The technique called for cutting out the growing point from the 
cyclamen tuber (something like removing an eye from a potato you are 
going to eat for dinner), washing the wound with alcohol to remove 
the slime exuded by the tuber, packing the wound with sulfur, and 
replanting the tuber. He added that the growing point itself could be 
de-slimed with alcohol and sulfur and itself replanted, though there 
was no guarantee it would survive.

After removal of the growing point, dormant buds on the surface of 
the tuber would then sprout, allowing the tuber to then be divided 
once these were well established.

I do not know what success rate, if any, was claimed for this 
technique, but one can only suppose that it was good enough to 
warrant risking the loss of an uncommon form.

An analogous propagation trick for crocus forms that do not multiply 
vegetatively was to pluck the growing point out of a corm when it had 
started to elongate. As with the cyclamen trick, this caused dormant 
buds on the surface of the corm to grow, each one forming a new corm 
in due course.

As for sulfur, I remember Paul Christian's comment that it was a very 
good fungicide and stayed where you put it. To this day I dust cut 
surfaces with it when dividing certain plants, e.g. Eranthis tubers.

I don't recall what time of year was recommended for these treatments 
but suppose for crocuses it would have been in late summer when they 
begin to stir back into life after summer dormancy.

Diane Whitehead was very likely at the same presentation and may be 
able to comment.
Rodger Whitlock
Victoria, British Columbia, Canada
Maritime Zone 8, a cool Mediterranean climate

on beautiful Vancouver Island

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