I think that is going to depend on where you are located. You should go to your profile page and add your location and hardiness to under the public profile link. Even if you are late to winter sow it is still not to late to sow Hardy Hibiscus seeds.
Hi, I'm in PA/6b and I ws'd mine 3/11 last year and put them into their own pots mid-May. We had a prolonged very cold winter so maybe I got lucky by planting in March, but they all flowered late summer. Good luck!
Name: Ginny G Central Iowa (Zone 5a) Plant Addict!!
I just received some Hibiscus seeds and was going to try to winter sow them in Iowa (zone 5). Does anyone know how deep I need to plant them in the milk jug and if I need to do anything to the seeds prior to planting them? Thanks!
Hardy Hibiscus seeds don't really need any cold stratification or special treatment, from personal experience. I just cover the seeds in about a centimetre of soil and keep the soil moist until germination occurs.