Sunlight, no matter how strong is very limited in the winter months and seedlings will strech to reach it creating weak and spindly stems. Stong seedlings need summer sun or 16 hours a day of light about 2-3 inches away from the bulbs. A grow light is not needed. A simply 4 ft shop light will be well worth the $15. It is a lot easier if you hang it with chain or rope so you can keep adjusting the height of it when they grow.

I bet your yard will look like a purple clouds when they are in bloom... very pretty! Have you thought about planting creeping phlox? I have a large area by my sidewalk that the neighbor dogs piddle on and it is filled with thyme and creeping phlox. It is so pretty in all seasons because of the different foliage.

Because you are starting in seed plugs, they will need to be re-potted into larger pots to grow properly. That is a lot of plants, you are going to be taken over by tyme : ).

I hope that helps.

Keriann~

Thyme does beautifully with wintersowing... which would save you the expense of any shoplights at all... you could also use larger containers and avoid all that potting up, since it sounds like you have a lot more space to work with outside! =)

1500 is a lot of plants to gamble on winter sowing. A late frost could kill all your seedlings while more mature plants are cold hardy to zone 4. I'd go with shop lights. If you do winter sow them be prepared to cover or re-sow if you have a late frost.