You'll definitely have to check out the zone info for any varieties you are considering. Some are and some are not hardy in zone 6. I've had reasonable luck with the munstead variety overwintering so long as I have it in a sunny well-drained location.

FataMorgana

I think you'll do much better starting them in pots. I find that light helps germination, so I surface-sow them or just barely cover the seeds with growing medium.

I assume that you're going to grow some variety of "English lavender," Lavandula angustifolia. The Munstead and Hidcote varieties are sometimes sold as seed strains, but any L. angustifolia should do fine in zone 6.

You might have good luck with Richter's of Canada. I've ordered plugs of "English lavender" from them and got a good variety of foliage types, sizes and colors in the final plants. Their seed prices are quite reasonable.

Here is a link that might be useful: Richter's

I am in 5-6 and Provance and Grosso do well in my part of Kansas City. I have only had one Hidcote live over the winter for me but the larged leafed ones do well. They will after about three years develop this really wonderful (to me) twisted woody stem so if you have a place that you could view from the side like beside steps.

The intermediate lavendins (Grosso, Provence) will do well in zone 5-6 and are large bushes with heavy production. Provence is my favorite for soaps and sachets but is not appropriate for dried arrangements (the buds "blast" off the stems with a slight touch once the stems are completely dry, the color fades to a silver gray-blue). Grosso has a darker flower color, and sharper/stronger scent, and will hold to the stem once its dried for floral arrangements.

Any of the English varieties will suit for zone 5 as well. The stems are shorter and the flower heads smaller than the intermediate varieties but you have a great choice of flower color. I've done some nice package tags of dried lavenders in a array from dark purple (hidcote) to blue (munstead) to pink-white (Jean davis). I use these little floral package tags in place of bows.

None of these lavenders will make it through the winter if placed in an area where water pools. Make sure you have good drainage and direct sun of >6 hours when you place your lavenders. I'd recommend getting plant plugs. Seed germination for lavenders is low and you will not get Provence or Grosso from seed. Also, you will not get "true" hidcote from seed.

Grosso and Provence are good plants, but they can't be started from seeds. As I understand it, all lavandins are sterile intergeneric hybrids and can only be propogated vegetatively or by crossing L. angustifolia with L. latifolia.

I've had good luck with both wintersowing and starting indoors (December) using the moist coffee filter/baggie method. Once they sported the first root (radical) I potted them up individually into snack size pudding cups, re-inserted them into ziplock baggies until seed leaves sprouted.
As for winter hardiness I have good luck with 'Munstead', 'Vera', and 'Grosso' in infertile, alkaline gravelly/sandy soil.
Mustead is a good self-sower too and I'm still digging up and moving little babies since spring as I find them :D

Vera

I have lots of cuttings you are welcome to, that is how I started all of mine and it is very easy and faster than seeds. vickie, tidewaterlilly