I recently got a small hibiscus. It's the sort that you see used as bedding plants around buildings, esplanades, etc. They don't get very large, but then, they're only in these beds for a few months. The label says it won't get more than 18" tall. I find this very hard to believe. Have they used a growth retardant on these plants? Does anyone know what kind of low temps they can take? Our winters don't get really cold most of the time, but we do have mild freezes from time to time.