Check out the 'winter sowing' forum.

You didn't provide a link to a picture of the structure you're referring to.

Rayama, I recommend winter sowing for all your perennials and hardy annuals, too. It's a great method, cheap, and your plants are already conditioned for the growing environment, so you don't have to harden them off. I use my recycled 2-litre soda bottles. Let me know if you want any other info. I did it this year for the first time, and it was a very successful endeavor. The "greenhouse" environment provided by your containers, prevent insects and birds from stealing your seeds, from being blown around by the wind, etc. You use regular potting soil for the seeds, not seed starting mix, and just put the containers outside. You need to watch them occasionally because they do dry out, but not often. Also, if you don't use a potting soil with fertilizer in it, you would need to fertilize the plants with a weak solution once they come up.

Susan

Don't laugh, but another item that can be used as a "mini" greenhouse, are the containers that you get for doggybags from Cracker Barrel. The lid is clear so you can watch for seeds breaking through. I used it to start my Moonflowers this year.

I used a chilly (50s-60s) 4-foot-wide interior closet one year, exchanging my husband's clothes for wire shelves and hanging fluorescents, and it worked wonderfully. No problem with getting too warm, then too cold, not enough light, et cetera.