Plant them early in spring, as soon as you can. Mine grew well until temps got into the 80s, then they began to get powdery mildew. If you keep them well watered and partially shaded, ymmv. Maybe look for a mildew-resistant variety.

Should not be a problem in zone 5. But they are best as a spring or where conditions permit a fall crop. They do not like July -August most places. As happyday advised. plant them as early in the spring as possible at least a month before your last frost date. They are frost proof until blooming.

Frost proof until blooming, huh? I didn't know that. I plan to grow them from seed, so I I will place them out earlier than the rest. I may plant them north of the corn so there can be some shade...

Thanks!