Hi Koen, from years of growing in warmer climates. Just to mention a few. Red Charm a definite no go. Red Charm, it blooms 1 week before Coral Sunset in Belgium and in early climate it flowers 1 week after Coral Sunset, Red Charm will germinate with first the bud then the stems. Bowl of Cream is one of the lactic that is best suited for warmer climates.
Climate change in Morocco made us move up the mountain. When started 14 years ago we had 15 cultivars at 700 meters altitude, Now there is just 1 left. Coral Charm.
One additional note. We had Bridal shower on 700 meter. Few flowers and mostly deformed, but big bushed. Lots of foliage. We dug them up after 4/5 years and they had enormous root systems. We could divide them in 6 to 8 new divisions.