I learned that these are for zones 3-7. Are these easy to grow? Is there special care needed?
Kidling is a Division 7 Y-Y, and is a miniature. Often miniatures are given special planting attention, maybe being planted in raised beds or areas, in the North anyway, that are sort of protected.
I have grown Sun Disc as well as Sunndial which are also Miniature Division 7Y-Y, and not had any problems with them.
I'd just suggest that they be planted in an area that has good drainage, and that will not be regularly watered during the summer months when they are dormant.
Here is a link that might be useful: Kidling at Daffseek