Legalily said:I tried hibiscus seeds couple years ago. Seems I need a few lessons 
The seeds need scarifying. (Think of a trip through a duck's gizzard.) Just rough up any part except the pointy end.
I use a nail file. (I tried nicking with a knife, but exposing the white part killed them - you just need to scratch the coat enough to see a change in the shade of brown) I soaked them 24-48 hours. I soaked mine in WARM water which I changed 2 or 3 times a day to re-warm it. If they plumped up slightly and sank, they were ready. I had to re-scratch a few, and the ones that didn't sink were usually duds. After soaking, they sprouted in 4-7 days at room temperature after planting 1/4 inch deep. (I planted them under grow lights inside at a room temperature of 70-72 degrees F.)
They can be started outdoors after all danger of frost is past. However, if you want to see any blooms this year, an early start under growlights or in a sunny window will help. The ones I started in December got leggy, but the ones I started in February did better.
I planted them in the ground after my established hardy hibiscuses broke dormancy (early May here in zone 6A).
In your zone, you should be able to plant them in the ground by mid-May. They will be easiest to keep alive in ground rather than in pots, because they are water hogs. They are not at all fussy about soil - places that are too wet for other plants but are in full sun are their favorite areas.
As babies, they cannot take frost. By next Fall they will have good roots and simply die back to the ground and go dormant and the cold won't bother them a bit.
Those are the directions I've come up with for growing hardy hibiscus from seed. I'm getting reports of good germination. Let me know if you figured out what went wrong last time and want to try again!
