Don't you hate it when....

[Eeyore]

Both factors would play a part Patty. The length of daylight hours, the average temperature, humidity, soil as you mentioned and the number of days of warmth each season. All these factors will also determine if a plant acts as an annual or a perennial in your garden too.

[patty]

Makes sense Patty. Do you happen to know where the Hibiscus originates?

Hi Scrap, with so many species of shrubs, herbaceous plants that make up the hibiscus, I'm not sure where they all originate. I have two perennial hibiscus' that are in the mallow genus. One I bought called swamp hibiscus is native to Florida **I think. They naturally occur in swamps and in marshes, and grow to approx. 7 ft tall. Now here in my dry sandy soil it grows maybe 5 ft, hence my opinion on the soil types factor in on the overall growth of your plant. Zones, I think, are more for winter hardiness. I hope this helps.