This doesn't need cold stratification in my experience. You could soak seeds in warm water overnight but I don't even think that's necessary.
There's also a variegated form of this tree/shrub that's very nice, and probably would be hardy for you.

Try asking also in the growing from seed and tree forums.

I've never grown it myself (would love some seeds!) but the following information might be helpful to you.

Propagate by seed sown in spring at a temperature of 22-24C. Germination takes about 18 days. Grow out for a year before transplanting. Plants will be 60cm or more at that time, and further growth is also rapid. Can also be propagated by cuttings, which are easy to strike in warm weather. A very resilient plant which can grow rapidly. It is frost-tolerant, but may die right back to the root during extreme winters. It is slow to set leaves in spring, and late to set flower. Moderate to heavy pruning in winter will stimulate growth. Will grow in most soils, but it must have good drainage. Plant is susceptible to root rot and nematodes, but is otherwise very hardy, and will even tolerate salty conditions. Grow in sun or partial shade, in moderate to moist soil. Best suited to tropical or sub-tropical areas. Growth rate is slower and mature height is less when grown in cooler climates.