I'm also a fan of Maria Mathilda, interested to know it does well in heat. I had it in zone 4b where it was very reliable and hardy; dieback not much below the snowline and got to be a substantial bush perhaps 4-5 feet. Definitely not a miniature; larger flowers too.

This is a very special rose. But how it got classed as a miniature is a mystery! The flowers get up to 4" across for us and the plant grows to over 7' tall here in SoCal. The pure white blooms open with a grace and poise that is set off beautifully by the large and prominent eye of yellow stamens in the center of the flower. And they are fragrant. We had poor success with Margaret Merrill. Maria Mathilda has the same look on a much healthier and prolific plant.