is heliotropium arborescens a perennial in zone 10?. Summer is very harsh here and reaches over 100F while winters are mild not below 5C. Can i fall sow its seeds to bloom in summer?
As long as you don't go below freezing, it should grow as a small perennial shrub. You can try growing it from seed, but seedlings may not be as strongly scented as plants grown from cuttings, so if it's the fragrance you're after, stick to cutting grown plants.
It should be able to take the heat, so long as:
1. Do NOT let it dry out, it really needs constant moisture at the roots, and,
2. Do not locate it in full sun in the summer or it will bake, and the flowers could easily burn in hot, dry sun.
Hope this helps!