You can get 2-4 weeks head start on putting plants out. My growing season is much shorter than yours and I rely very heavily on my cold frames to extend the season.

I use cold frames to harden off my seedlings, putting a quilted moving blanket on top if it's going to be unusually cold. It gets them out from under the lights and out into natural light faster. This leaves room under the lights for the plants that really can't go out until it's warm (peppers and eggplants).

I also plant directly into the ground under cold frames that have been in place for a couple of weeks to warm the soil. Under two of my cold frames I buried a heating cable, which gives me some extra protection.

If you normally put a plant in the open garden on April 15th - it's pretty safe put it in the cold frame by April 1st. If the weather is expected to be mild, you can put them out in the cold frame even earlier.

Most important - you must keep the plants from getting too hot. I have one purchased cold frame with an automatic opener on it. When I see that one opening up, I go out and uncover the homemade ones too.

As far as tomatoes, I tried winter sowing last year with great success. The winter sown tomato plants were smaller to start, but they caught up to the inside sown plants by June. Just put your flats of seeds right into the cold frame now. They will come up when it is time for them.

I'm winter sowing all my tomatoes this year. No lights, no hardening off. (Again - just don't let them get too hot during the day). Easy.

Depends how much work you want to do. I use coldframes all winter:

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Note how the foreground tunnel is venting. You must vent during the day and if it drops below, say, 25F with a single pane of glazing, you'll have to cover (depending on how thick the walls are). Two layers of glazing will take you to the mid-hi teens F (depending on how thick the walls are).

So if you are planting out/sowing, say, lettuce, onions, etc. I agree that you can get 4 weeks easy. You can get more if the walls are thick (e.g. 2 x __ dimensional lumber) you have double glazing and you cover when an Arctic storm blows through.

Dan

Dan, that looks like a sweet cold frame. I'd do that all winter long too, but it's so dreary in our winters that it doesn't work so good, not enough light for growth.

In general, I agree that cold frames are a great place to get an early start on cool season crops like lettuce, cabbage, chard and broccoli. I have all those started already in my cold frame but I think I started too early as they light levels are still to weak. I have a Jewel 1500 cold frame that I would highly recommend to folks except for the fairly outrageous price. The insulation is terrific as I sometimes find ice on the outside of the cold frame while it's 50-60 degrees inside.

I also use cold frames/tunnels all winter. I get the plants in during the fall and some growth on them then, and the plants hold fine all winter for harvesting. They do not grow much in cold weather, it's more like a natural storage system. I layed remay in mine this year because it was so darned cold here.
We pulled out the seed starting cold frame yesterday, they don't make the one I have anymore. It is very simple, just greenhouse type plastic, sort of corrugated that folds together. Works really well here. At church I use straw bales with an old glass window over top. We make sure they are screened so that we can just open the window to vent.
We are planning to eventually build cold frames with old windows and block/brick and some flat insulation.

Thank you TC. That dark triangular thing in the near distance covered in snow is my other frame. I built that one too and the walls are ~R 5.5 or a bit more. I can open it in the sunshine at -10F and the vent will open, and covering the glazing that night will still fall to 50F in the morning. Built with salvaged wood from housing development.

Anyway, you can start much earlier depending on the quality of your cold frame. Takes about a week or max two weeks to thaw and warm soil for germination, leaving the top closed. My season in both structures will be done by April 15 here in Z5, so I can get the other stuff started for summer (last frost ~May 15 or so.

Another thing relevant to OP: I use walls o' water to set my Toms out 4-5 weeks early (the green things against the wall):

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Then you can save one coldframe for hardening off, and another for greens to start soon, and maybe another for beans or something, or to warm soil...many possibilities!

Dan

Dan,

I need to stop by your garden one day and observe up close.

Greg

And Dan's south-facing tall masonry wall is a big deal in of itself, because it blocks the coldest wind and is a solar collector and storage bank. In a climate like florida's, for example, that can be all the frost protection that is required. I'm planning to build a masonry wall specifically to protect avocados, bananas, etc.

pn has it exactly. If I didn't have this arrangement and the positioning of the house on the SW side of a hill (cold air drainage), I wouldn't live in this neighborhood. Way back in history, walled gardens in Babylonia were the first constructed microclimates. Cold frames push that idea further, and with an auto vent opener you have a portable greenhouse.

Any time, Greg. After I get back from Phoenix I'll put more stuff out (mid-March).

Dan

Dan, I'm curious, what city are you in or nearest? I think sunshine where you are is much more abundant than where I'm at. So coldframes here aren't very useful til mid March or so. It's not that our nights are cold it's that our daytimes are too often dark and surprisingly often we have the lowest daytime temperatures in the continental US.
It looks like you have a commercially produced termperature-responsive vent? If so, how long do you expect that cylinder to last? I'm in my fourth year with one of those cylinders and it's now starting to wear out.

TC, I'm SE of Denver. We have tremendous and powerful sunshine here (and wind). I used to live in Seattle so very familiar with the climate in Cascadia.

In the big frame I have a Bayliss opener on its third year, expecting two more out of it. In the foreground that is simply a Harbor Freight vent, as these are field trials. No idea how long they will last - I collect the 20% off coupons and with them vents are under $20.00 incl tax so low entry cost.

Speaking of low entry cost, I like what girlgroupgirl wrote above about strawbales and windows. I did strawbale one year in WA state and worked pretty well.

Dan

I constructed a simple cold frame last fall and was very pleased to be able to harvest leaf lettuce, spinach and cilantro all winter long. I used an old double paned patio door for the glazing and I covered the whole thing with old blankets when the temps dropped into the teens. Temps in the cold frame never got much below 30 even when the outside temps dropped to 10 degrees. I was really impressed with the cilantro which really seemed to respond well to the fluctuating temperatures and was very quick to put out new leaves as I cut them to eat. BTW, I'm in the same zone as the original poster. I'm in the Shenandoah Valley of Virginia and we get a lot of sunny days most winters.

I use a cold frame too. mine has a duble layer of bubble wrap on the lid end with one of the shetts sandwiched between to clear plastc garbage bags. It comes out to 6 layers. It got down to -4 outside this winter and was only 17 in the frame. I planted in late november and the seeds planted then are just now starting to grow. I've use other cold frames in the past.

If you want a harvest through the winter plant in late summer so that the crop is ready by the beginig of winter (hard freezes). For spring you can plant at least a month early or plant a couple weeks before hard freeze and overwinter seedlings which will take off as soon as they are ready in spring.

I was thinking of getting a wall-o-water to see if I could get tomatoes a little earlier. I was also thinking of making a 3x3x2 wood box a slanted roof and an old window. Then put a automatic vent to open/close window as needed.
Something like girlgroupgirl has. Anyone know how the wall-o-water does?

Just did a quick check, and Oregon is on the same latitude (approx) as the South of France, so you should have plenty of light in the winter

Forensicmom, cold frames are great!

To get started, you should get one of those min/max thermometers (like: http://www.amazon.com/Thermometer-Mercury-Magnet-Sper-Scientific/dp/B001EUCSSC ...not that I'm recommending this one).

Once you know the temps, you'll know when it's safe to put plants in there.

I found it took a few years to optimize the whole process back in Jersey. If you start the plants too late, there's no benefit and if too early, then they outgrow the cold frame.

Oregon is on the same latitude (approx) as the South of France, so you should have plenty of light in the winter

*chuckle*

Good one! Thanks for the laugh in the morning!

obrion, I use WOWs all the time. I get 4 weeks before last frost, more than that and they start growing out of the WOW:

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Put a 5-gal bucket inside then fill them.

Dan

Dan, I think from your advice I will get one. Menards have them and I was wanting some input and you made me make up my mind. Hopefully I will eat a tomato a bit earlier this year.

They should come in packs of three, obrion. Get the repair sleeves too if you don't have bikes. WOWs are pretty much standard around here.

Dan