Rich's Dwarf
Quince in the US

Right, so quince seeds need a good start. You'll want to sow them indoors, really, in pots or trays with some good quality seed compost. Depth-wise, about half an inch (1.5 cm) is plenty. Timing depends a lot on your USDA zone, you know. For zones 5-7, you're looking at March, April, or May. Colder zones might lean towards April-May, whilst warmer ones can even sow in late fall or early winter, sometimes January or February. Keep the compost moist and warm; they're not the fastest to get going, to be honest.

Once your little quince seedlings have a couple of true leaves, you can prick 'em out and pot them up into individual small pots. Give them a bit of space, like. Before they go out to their final spot, you'll need to harden them off for a week or two, gradually getting them used to the outdoors. Plant them out once all danger of last frost has well and truly passed in your area. They're trees, remember, so give 'em plenty of room, maybe 15 feet (4.5 meters) apart if you're planting more than one. If you're trying a dwarf variety, a big container works a treat.