It protects the seeds and seedlings from birds, torrential downpours, wind blowing seeds out or rapidly drying the soil surface. It also helps retain much of the moisture. When it is warmer out the water starts to evaporate, but much of it condenses on the lids and falls back down into the container. It also helps keep is slightly warmer and provides some protection from frost as well.

That makes a whole lot of sense.

What molanic said. If you don't close the container, it would be like direct sowing--the seeds are not likely to stay where you put them, especially if a hard downpour and heavily melting snow cap can wash them out of your container and into a mixed pile of seeds in an inhospitable area.

With the condensation of the closed container, you don't have to water (or mist) all of the time to prevent the seeds from drying out. But the vent holes 1) keep the soil from staying so wet the seeds rot and 2) keep the heat from building up to the point where seeds (and germinating seedlings) cook in the sun or rising temperature in spring.

Most seeds perfer a higher and more stable humidity than is common outside for best germination. The closed top system provides that extra boost as well as allowing less work of watering.

These needs are why plants produce so many seeds; the germination rate in completely uncontrolled settings is terrible. When you only have 25 seeds instead of hundreds, you need a better success rate.

The idea behind wintersowing is to allow Mother Nature to do the cold-heat exposures that many seeds need to germinate. For other seeds that don't need stratification of any sort, wintersowing just gets the seeds out there so they germinate when the soil temperature is right and the seedlings grow on. For those the higher humidity is even more important.

Wintersowing is about efficient germination and getting strong seedlings with minimum work and more unlimited space to sow seeds than most of have room for under indoor lights.

Molanic has summed it up perfectly for you.

I'm a "veteran, an oldie" in the WS forum now. this is year #8 for me and it's the simplicity of Winter sowing that is the key to it.

Read and re read the FAQ's as they will help answer many of your questions.

WS in containers with covers, well it provides a more controlled environment than direct sowing or just putting the seeds in pots and hoping for the best.

Did you ever wonder why the seed pods of most plants have so many seeds in them? That's because mother nature wants to be sure that her vegetation continues to self sow and continues to propagate itself from year to year.

Since those seeds also have to fight the environment around it to survive, IE birds eating the seeds, critters eating the seedlings, torrential rains, flooding rains, floods, snow melt, various temperature extremes that the natural environment that mother nature has created, her solution for all of this was to make sure that her vegetation produces enough seeds to have a chance to reproduce.

Along comes man, to help the process along, but it was a complicated adventure that still fights lots of elements and lots of extra work.

Then, thanks to Trudi, along came WS and the ideas of taking the best of mother nature, along with some common sense observations of how things do and do not work well for mother nature, and "fix, solve those risky problems" that occur when mother nature is left on her own to do the work.

Those fixes, are the covered containers, that help to prevent the natural occurrence of birds eating the seeds, critters burying their treasured nuts in the soil, water washing away and with it all the seeds that will then show up where you don't' want them, provides a bit extra warmth, so that the soil warms up more quickly than the ground, keeps moisture in for longer periods of time and sure does help to keep some of the weed seeds from getting in their as well.

Take it from one with 8 years experience, WS is the easiest way to start seeds, the least stress way to start seeds, and provides you with an abundance of seedlings, healthier ones than you've ever had in your life and you will end up with more seedlings than you know what to do with.

Just get those containers outside and let them do their thing with mother natures help and sit back and watch the wave of green come to your yards.

There is no need to fret over the seedlings, to many in the container, etc. they will be fine on their own.

Fran

To keep the squirrels out of them! The little buggers live year-round here, even in the snow, and LOVE to dig up fresh soil. My seeds would never survive without covers.