I live near Boise, Idaho in Zone 7 and am wondering if I could start growing salad greens right now in a raised bed with some sort of protection? What type of protection should I use, frost blanket and/or plastic covering? What seeds would you suggest?
Attached is a picture of my growing space and it is on the south facing side. The boards are covering the soil since my puppy likes to sit in the bed.
In my view your biggest challenge with trying to grow vegetables right now is not the temperature but the amount of daylight available to your plants this time of year. This will limit the growth of your plants even if the temperature is at a level that they would normally grow in. With a good plastic covering and a frost blanket for cold nights you can warm up the soil and the plants a fair bit and keep them warmish but the lack of sunlight will slow them down.
My understanding is that winter gardening involves getting the plants started in late summer so they have time to grow and mature. Then they're covered and protected from the cold and harvested throughout the fall and winter. But they don't tend to grow much during that time.
If you have a greenhouse with artificial lights setup then of course you can keep the growth rate up by artificially extending the length of daylight in addition to keeping the temperature up.
Given the lack of daylight I would imagine leafy crops would do the best right now but I'm not sure if they would grow fast enough to make it worth it but I have never tried planting vegetables this time of year... I have seen some seedlings coming up around my place from self-seeding plants but they aren't growing much despite the days being in the 50s and nights above freezing.
But all that being said I don't have a lot of experience with winter gardening. I tend to rely on plants that overwinter without protection and just harvest from them.
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Otherwise, you can look at Winter Sowing, using that space (assuming puppy won't knock containers over) to get a jump on the weather - http://www.wintersown.org/ is the classic resource but if you google "winter sowing" you'll find lots of other, sleeker, web sites.
Or once things start warming up, you could put some old windows over the bed to act as a cold frame, again to get a jump on the weather.
I'd say otherwise you're not going to be able to plant until March - radishes, frisee, and peas will start early and give you salad vegetables (pea shoots are tasty!)
We're in zone 7 too, though further to the north (in the Netherlands). Still, I think the growing conditions in winter are comparable. As the previous commenters suggested, daylength is a limiting factor for winter growing and most hardy leaves need to be started much sooner. We start our hardy lettuces at the end of August/beginning of September and sow other hardy leaves such as mustards in the second half of September at the latest. Corn salad can be started in October. The salad plant that in my experience is the least sensitive to short daylight length is winter purslane and it even survives outside without protection, though it crops much more abundantly in the cold greenhouse. Herbs like parsley and chervil are also very good value.
In your case it’s probably best to delay sowing until February when the days start to lengthen again. And next year, start your winter crops in early fall 😊
If you're interesteed, here's a video on the winter salads we grow in our unheated greenhouse:
I am going to go ahead and throw my voice in with Daron. I do think the biggest issue is going to be sunlight.
But I will go ahead and conjure up a thought that may or may not be helpful.
If you want to try a winter garden starting now, my thoughts are first off to start small. It is a whole lot easier and probably more productive to tend to a small garden as opposed to a large garden. Since it is mid-late December, I would also go with a relatively simple choice.
I would try growing in some 5 gallon buckets. Buckets will be cheap and easy to set up. I would try to grow in maybe 4 buckets with a 5th bucket in reserve that I will get to in a minute. Fill your buckets with the absolute best potting soil you can get your hands on. Make some sort of frame covered with a transparent but durable plastic tarp or some other material. Years ago I replaced a French door with a slider. I had a friend who took the old French door and used it to make the lid of a cold frame, a lid he could open at will.
At any rate, make your frame. I think Daron is correct in that lack of sunlight is going to be a big problem. If you feel competent, maybe you could make a series of incandescent grow lights to provide both light and heat. The downside of incandescent is that they use fairly high wattage and LED lights will be safer and easier to install, probably have a better lighting spectrum, but will add almost no heat. I would be tempted to go with the LED’s.
This is where that extra bucket comes into play. I learned a long time ago that I could keep my childhood outdoor pet cat warm overnight if I put hot water jugs in the back of his little crate that became his pet house. He stayed warm all night long—90 degree warmth when it was -25 outside and probably-15 in the garage. I would take that five gallon bucket and fill it with hot tap water. Even better would be to boil some or all of that water just to make certain that it is hot. Put the lid on the bucket (make certain that you get a lid) and place the bucket in between the other buckets of garden soil. Make certain that all buckets are sitting on wood or something other than cold ground or cement (even worse). That hot 5 gallon bucket will stay plenty warm all night and as long as you fill with hot water just before going to bed. Check it in the morning but I cannot imagine that it would freeze unless it is directly exposed to freezing temperatures. Make sure that your little greenhouse/cold frame is protected from wind and rain (you don’t want water to leak into a moving part/hinge and then freeze—that’s bad). If you get really ambitious you might consider some styrofoam insulation to insulate the floor and sides. You can get this easily and cheaply from a hardware store. But this is strictly optional.
Getting good grow lights will provide the light you will need. You might even think about having a second reflective/opaque cover to both insulate and reflect light back in. But again. This is optional.
I would think that by giving your little greenhouse the 5 gallons of hot t water would provide plenty of heat. And if things just don’t work, since the plants are in buckets, you could easily bring them inside if you needed.
These are just my thoughts and take or leave them as you feel appropriate.
Best luck and please keep us updated. I for one am curious as to how your project works out!
I'm in zone 5 I believe, USDA zone 5, not permies zone 5 I do very little outdoors in the winter. I just cover and keep my late fall crops as long as I can. Right now I don't even have a greenhouse, I just cover my containers that are set outside. For starting new plants the sun is going to be working against you this time of year unless you start them indoors with a grow light to encourage the vegetative growth. I have two grow lights inside and a few salad green trays. For quick greens in the winter you may want to look into sprouts or microgreens while waiting for your salad to veg long enough to put out.
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