The most prolific bloomer of the Ag-Canada roses, according to a 1992 Horticulture article by Ian Ogilvie and John Arnold, is the medium-red shrub rose 'John Franklin'. Unfortunately, although Ogilvie and Arnold listed 'John Franklin' as having medium resistance to blackspot, John Franklin is one of the worst of the Canadians for disease resistance in my Kansas garden. I might see the advertised 14 weeks of bloom on him, but if I don't watch and spray this bush, 10 weeks of his bloom will be carried above bare-stems.
'John Franklin' is otherwise a really nice shrub rose, with clusters of semi-double flowers appearing in rapid succession. This pink-rose-red tone is not my favorite color among roses, but if you like the color, you'll see a lot of it on this bush. Bred by Dr. Felicitas Svejda in 1970, and introduced by Ag Canada in 1979, 'John Franklin' is a well-mannered shrub rose of the Explorer Series that has matured at about 3 feet tall and 3 feet wide in my garden, a great big red ball without many thorns. 'John Franklin' is very hardy in northern gardens, but alongside the lack of disease resistance I must also note that I find little fragrance present in the blooms. The seed parent is believed to be 'Lilli Marleen' and the pollen parent 'Red Pinocchio' X ('Joanna Hill' x Rosa spinosissima).
'John Franklin' is likely a great example of a rose whose blackspot resistance may vary depending on the exact endemic strain of the fungus in a garden and on regional environmental factors. Ogilvie and Arnold listed 'John Franklin' alongside 'Champlain' as having medium resistance to blackspot, but I find 'Champlain' to be a far more superior rose in blackspot resistance, bloom time, color, and overall garden impact. Helpmefind.com states that 'John Franklin' is "very disease resistant," although one member of that site comments that he is prone to rust in California. The red hue of this rose also seems to vary by location, with some pictures on the web appearing almost orange, and others near-crimson.
'John Franklin's explorer namesake was a Rear-Admiral of the British Navy who perished in 1846, along with his starving, lead-poisoned, cannabilistic crew and his icebound ships, during an attempt to chart the Northwest Passage. In the case of 'John Franklin', the rose, I suspect that over the years horticulture may well imitate history and we won't see much of this rose except in those very cold Zone 3 and below areas, where anything that blooms is still welcome and blackspot doesn't grow well enough to bother roses. And, of course, as global-warming continues, this rose is going to have less and less land to grow on, since it won't grow in the increasingly open seawater above the Arctic Circle and the Zones are moving ever-farther north. Does it even snow in Canada anymore?