Toughness seems to be combination effect. If both parents are weak for cold climates , most of the offspring will be weak. They all seem to fit on a "Normal" distribution curve. The centre point of this distribution curve is determined basically by the average toughness of the parents. Thus two weak parents can produce an offspring that is tougher then either parent but again most will be weak, some weaker, some stronger. If you have only a few strong offspring from a cross you have very limited choice to pick good offspring with other good qualities. Thus if out of 40 children of a cross, only 2-3 have good colour and form etc and only 2-3 of a weak cross are strong then you get to choose the best of 2-3 rather then the best of 40. If one of the weak parents have a tough parent you seem to increase tour chances.
Chuck Chapman, Guelph, Ontario, Canada. Zone 4/5
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