Brinjal Seed is a warm-season crop that thrives in temperatures between 70°F and 85°F (21°C to 29°C). Start your brinjal seed indoors 8 to 10 weeks before your region's last frost date. This will give the seeds time to germinate and grow into sturdy seedlings before transplanting them into the garden. If you live in a mild climate, you can also sow brinjal seeds directly into the garden once the soil has warmed up in spring.