I have a Plectranthus amboinicus plant in my garden. I live in Canada, hardiness zone 5. The identifier stick that came with the plant states that it is a perennial. However, everything I've read seems to indicate that it is only perennial in zones 9 or 10. Is this true?

Also, how can I dry it please? The leaves are thick and fleshy and I've tried air drying it before but the leaves just shrivel up and turn a muddy brown. Is this what others do?

If it's going to die in the garden then I'd like to remove the leaves and dry them for the winter.

Thank you very much!
prebanks