A warm welcome to the Winter Sowing Forum. Have you had a chance to review the FAQs on this site? I believe the link below will answer your question in depth, as well as a lot of questions you didn't you had. Yes you need ventilation. Also take a look at wintersowing.org. You will find both education and free seeds there. You will also find free seeds in the Exchange section of this forum. Once you had a chance to review the FAQs, stop back by with all the questions you can think of. This is a warm and helpful group. Welcome aboard. Seedmama Here is a link that might be useful: Winter Sowing FAQs

Paulan, I'm a fellow zone 5 wser and here's my take on things. First of all, I hope when you say "top" you don't mean the screw cap, as that should never be on. As to opening the containers, I judge by how warm they get inside and how hot the air temp is. This usually occurs sometime in early to mid May in our zone. We are expecting some very warm weather for a couple days next week. I will probably throw a sheet or garden blanket over my sprouted containers to keep them cooler. My sprouts (about 100 containers or so) are still very small due to cool temps this past week. Most do not have their first "true" leaves yet. I also check the 10-day forcast at weather.com. It all depends on the forecast for night temps. A final note concerns that fact that if I open all my sprouted containers too soon, I will have no place to walk on my deck! Planting out time is still several weeks away for me unless the 10-day forecast this weekend shows night temps in the mid to upper 40Fs. I also go by root growth. Once I start to see strong root growth nearing the bottom of the container, I figure the sprouts are strong enough to take whatever Ma Nature throws at them. Good Luck!

I cut the milk jug in half just below the handle and then use a hole punch and punched holes in each corner then use some twist wire found in the floral dept. from walmart to keep the two pieces together and also don't forget the drainage holes on the bottom of the jug. Note there is no keeping the twist cap to the jug, that is no longer needed now. The jug will sweat inside if placed in the sun but you do need to keep an eye on each jug for moisture levels vary. One thing I learned last 2 years was that a small blast on low from the hose works great. And to plant a few extra on the sides of the jug for just in case. In my case I would often find that germination in the center of the jug (where I watered it) there was low germination rate I figured the seeds were getting washed away to the sides I just decreased the level of water the hose put out, if this makes sense. And when the plants get big enough to handle the world I then take off the top part of the jug. And it makes it easier to plant out. HTH Paula

It is good for short-term, but WS is somewhat the opposite. You put your jugs out in winter, forget about them, and spring brings new shoots. They'd disintegrate like campanula said in the snows and rains. TP would be good for quick germination once the gardening season begins, though. Zinnias would love it, for example, since I often had them germinate in under 24 hours in very warm southern sunny soil!