North American Fruit Explorers mailing list at ibiblio

[Steven Covacci <filtertitle@aol.com>]

I'm planting the self-fertile, highly disease-resistant (including black-knot 
resistant) variety of European plum (P. x domestica) known as 'NY-9' (aka 
'Kenmore).
For a second plum - a purple-fruited variety, I'd like to go with either 
Imperial Epineuse or D'Agen.  However, President would be my second-choice, 
right after 'NY-9' for the sake of disease-resistance.  I live in the 
northeast (NJ).
Do you think I'd be better-off planting President and then, latter, 
top-grafting with the better-tasting Imperial Epineuse (or maybe D'Agen; aka 
D'Ente/707)?  I figure that if the top-grafted variety starts exhibiting 
high-susceptibilty to black-knot, then I can cut it back to the President 
variety which it the understock and frame.
Or would I be better-off just getting the better desired variety (Imperial 
Epineuse) and just keeping my eye out for black-knot, pruning it off.  One 
note is that if I just get a grafted tree of Imperial Epineuse, I would steep 
the graft union and get it on its own roots; however, if on President - there 
will be a graft-union between the President under-stock/frame and the 
top-grafted second variety, a point into which borers may enter, being that 
there will be a graft-union.  Sometimes, albeit rarely, the graft-union can 
get black-knot also.
Lastly, does anyone have an opinion as to wether the larger, freestone 
Imperial Epineuse is better then the more internationally utilized 
clingstone, smaller D'Agen (aka D'Ente/707 selection)?
Thanks,
Steve - NJ