The Reasons to put grafted part above the ground?
I understand that the bud union of the grafted rose should be at least 2 inches below the soil level in my zone 5 climate to protect from freezing temperature. However, in summer, we don't dig the soil 2 inch to expose this bud union.
So, in warm climate, why is it necessary to expose this bud union above the soil when planting? Is it important to expose to the sun or air? If so, why in a colder climate we don't do that in summer? What happened if you bury the bud union 2 inches below in a warmer climate zone?
It has been bothering me since it sounds like contradiction.