I've never done raised beds, but I don't see why it wouldn't work. As for other flowers, almost any annual or perennial you can ws would work -- petunias, marigolds, asters, rudbeckia, etc.

Thanks caryltoo! I will go without asters since I don't have any of them, but maybe larkspur and cosmos along with what you suggested and the poppies? Yes, I think I will just throw a bunch out there and see how what comes up. I can always start over if its a flop! I have tons of seeds that I had saved over the past several years and can risk losing a few! In the past I haven't had good germination when just throwing seed out on the ground, but am hopeful that the plastic covering it will make a difference. This will be a good week to get this going since its in the 50s (in Iowa) and I won't freeze while doing it.

Good idea! Just make sure you use rigid plastic or support the plastic very well. Otherwise when it rains, the plastic will sag down onto your soil and make a mess of things.

Agathafroo, it's actually an old home-made sandbox so its wood sides are higher than the dirt. I will also make sure its tight across to help it not sag! Thanks for the reminder!

I am also giving this a try. We placed a hinged lid with rigid plastic on a raised bed. I started sowing in seed starting trays in early February when I ran out of containers. As of yesterday, we had a few broccoli and cabbage sprouts from seeds sown on 2/10. Some of the annuals I put out two weeks ago are also starting to pop up. Now the tricky part will be managing the temperature swings in March and April. Please post your progress. I would love to hear what works well in this set up so I can make some notes for next year:)

today I sowed the poppies (2 kinds) in their, but didn't have time to cover it. They're pretty hardy seeds so should be ok if the squirrels will stay out. I am hoping to add more seeds right before I cover it.

I might try this next year. So, I'd love to hear how your sprouts do and if there is any advantage to that early a sowing to your overall harvesting schedule. Will you get more produce, too? I love experiments, :-)

The problem I see with this, if it is indeed winter sowing, is the different dates at which sprouts emerge. There is a wide variation and when will you remove the plastic? Some spouts may fail because of 'frying', some may fail because of freezing. There is also the difficulty you may experience in thinning in the raised bed. Just thinking ahead.

good points. Actually it got cold and I never got any more seeds in their after the poppies and I didn't even get it covered yet. I am hoping I can add some hardy annuals soon and then cover it, but will consider your comments. Mostly I think it may just give a few weeks head start to their growing. I never have much success at direct sowing except for poppies and larkspur so maybe I should just stick with those 2? Will think about it.

A Chicago member, Pitiminai, did this with success. I don't know how well searching will go I'll poke around for it.

Edited to add the link:
http://forums2.gardenweb.com/discussions/1737463/winter-sowing-poppies?n=19

So far this has still been working well. The hinged lid has been a major help. Most of the perennials have not done anything yet, but so far, I have cleome, delphinium, sweet pea, lavender, aster, and penstemon seedlings poking through (all sowed Feb 10th). From March 3rd sowing I have a few herbs, alyssum, blue flax, browallia, california bluebell, convolvulus, forget me not, cupid's dart, lupine, malva, monarda, nemophila, scabiosa, stock, hollyhock and zinnia. I will definitely say watering has been a chore compared to letting the jugs do all the work for me. I have all the seeds in 6 pack cells and no slits in the top. Things dry out VERY unevenly, but compared to balancing too much and too little watering with my indoor seeds, those outside in the raised bed are FAR more forgiving. I will see if I can figure out how to upload a photo. (Right now the poor little set up is covered in moving blankets. Here in the midwest we just HAD to have that late March freeze that I always gamble with.

I just took a peek at my box with a sheet of plastic over it and it seems to be giving me some sprouts! My set up is much simpler than jbzone6- yours is beautiful- but I don't have the skills for building. I have no idea which ones are sprouting since I planted a bunch of different things. I am guessing its the poppies since they are so cold tolerant and we've not had much warm weather here till today! This is so exciting!!!!

Thank you Maryjo! I wish I could take the credit but that was not only the husband's building, it was his idea. Congrats on your sprouts! I'm sure it will be even more fun as the plants take shape and you find out what is sprouting.

Is this the same idea as a cold frame? Congrats on your success!

Sorry, I don't know what a cold frame is, but it sounds like it would be like what jbzone has done. She can put actual seed trays in hers. Mine is just one old sandbox filled with dirt that is raked with pro-mix thrown on top and many assorted seeds sown over that; then I placed a large piece of plastic with holes cut in it over it all and fastened it into the ground with small stakes. stage_rat posted earlier the link that gave me the help I needed. I had a general idea, but with those tips from her link I was all set. I think it may work and have seen some sprouts, but hopefully they're flowers and not just some weeds!!!! I will have to be patient!

I thought I would post an update, before I forget. I attached a pic of the sprouts when they seemed to be at their height. The only ones that were not sown in there were the fivespot in the peat pots (which I have to say I will never use again).
What I have learned from this is the frame works well for sprouting seeds, but utilizing such small containers and having no holes, the watering, as expected, was very difficult. As the temperatures started to heat up during the day I had to water some containers nearly three times a day, which on work days is pretty much impossible. Over the last week or so, I also seem to have ended up with something nibbling on the stuff inside the frame. I spent a few days "rescuing" some things and potting them up. I will probably do a similar set up next year, but will save some of my pricier seeds for indoor sowing. I will also have to be more selective with my watering, rather than just hosing down the whole thing (naturally the stuff in the middle was soaked, while those around the edges were bone dry). Overall, I ended up with some good stuff....probably more than I know what to do with, but quite a few losses as well. Still glad I did it. Maybe next year I can start container saving sooner since they require much less work.

Maryjozone5, how is your set up working out?