I think two out of the three varieties of tulsi sold at Strictly Medicinal Seeds 
tulsi rama and 
tulsi krishna  are perinnials when grown in zones 10 and 12.
 
 I'm growing a 
temperate tulsi this year that is an annual but I'll save seed and expect to have it reseed some if I let a few go.  
 
 There are small pollinators that love the blooms  as do I for tea.  I cut leaf and flowers when the flowers are just open for fresh leaf tulsi tea.
 
 Was your plant labeled for variety?
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