Good afternoon Planting Oaks!
Yes, Stock is happiest in cool weather but there is a heat tolerant Stock out there called Katz. I've grown it in zone 4b where the summer ranges from 75 to mid 90's and it did great! The spicy scent took over the yard. I planted them in mostly shade due to the heat intolerance but they bloomed rather quickly. In our colder areas Stock is considered an annual. How lucky the Texans are to have this wonderful plant come back every year! I am so jealous!
They seem to be finicky to start from seed though. At least to me. This spring I planted 4 2" peat pots and none of them sprouted. With me & Stock its always hit or miss.
Katz is 16" tall, plant the seed 1/4" deep, it likes cool temps to germinate 60-65 and can take up to 20 days to germinate.
I think I'll need to relocate the seed trays to a cooler room and just be patient!
I hope you get it figured out next year. If you do let me know your secret!
