Which P. Nigra? From where? Any from anywhere? Isn't that a little
general? I'd trust a specific strain from a specific location - to try.
I believe what Rick Sawatsky was talking about was using wild or "pure" p.
nigra. The ironic thing is that nowadays there are very little pure sources
left, rootstocks of supposed p. nigra are a couple of generations away from
the pure p. nigra. The moral of the story is the more pure the source of p.
nigra, the better chance it will have of successfully pollinizing p. nigra
or p. americana hybrids. I would have to ask, but I assume that pollen from
pure p. americana would be a good source as well.
As mentioned in the article, hardy P. salicina hybrids from manchuria such
as Ptitsen #3, or #5, Fofenhoff, Ivanovka are also good pollinizers. I
don't know if these selections are widely available in the US, however.
South Dakota is supposedly a Japanese x american (p. salicina x p.
americana) hybrid, so based on the article, probably would not be a good
pollinizer. The Toka and it's sister Kahinta plums are p. americana x p.
simonii hybrids I believe, which may be good pollinizers to the p. salicina
hybrids.
Dean Kreutzer
Regina, Saskatchewan Canada
USDA zone 3