Season Extension Techniques: Cheap and Dirty Options

Sharon July 21st, 2009

I want a greenhouse.  No, I want a glasshouse, a true British style Orangerie and succession houses (and, of course, the extensive grounds to accompany it, and the private fortune,  as long as we’re dreaming).  I dream of wandering in winter into tropical glory, and plucking ripe grapefruit from the trees for my breakfast, while the scent of jasmine permeates my senses.

Ok, revisiting *this* planet, the one I actually live on, and the one that’s already suffering because crazy people want to live in the tropics when they don’t,  what I’d really like is an attached greenhouse on the cement slab that comes off my kitchen.  But the slab would have to be insulated and we’d have to find the money and the time to build it, which may happen eventually, but has not yet done so.  What I’d grow there would be cool season vegetables and seedlings in the spring.

Or I’d like a hoop house.  This is more viable, but requires some infrastructure work we haven’t gotten to yet.  My goal there would be to keep things over the winter in large beds, and maybe eventually go back into the CSA business, this time in winter.  But I don’t have that either.

I mention all these things I *don’t* have because I think it is important to realize how even in many quite cold climates, it is possible to use very simple, very low cost strategies to extend your season.  Despite all these things that I don’t have, let me tell you what I do have:

- I have fresh green vegetables grown by us from March to December or January, every single year.  This is in upstate NY, where our winter lows hit -30.  First frost is early October, last is usually late May.

- I overwinter produce every single year, including both hardy root crops and greens like kale, spinach, leeks, etc…

- I have two lemon, one keffir lime and one orange tree, a fig and a pomegranete, along with many smaller tender plants.

- I have fresh things of high nutritional value to eat all year round, produced here.

 - I start virtually every single one of my seedlings here, in the house, and use only a couple of hanging lights.  I use no lights in overwintering my tender plants.

- I have nursery beds for starting hundreds of perennials, fruits trees and berries over the winter.

I mention all this to give people a sense of what is possible with very little effort or input.  My tools for doing this include:

- Two “pop up” greenhouses (ie, they can be set on top of a raised bed or flat crops, one little stand up greenhouse (ie, a plastic cover over a plant rack that sits on a porch.

- Self-watering containers on a poorly insulated sun porch

- some greenhouse plastic and old window frames and some floating row covers

- Lotsa mulch and bales of hay

- My unheated, uninsulated garage

- A couple of south facing windows

- Willingness to experiment

I’ll talk more next week about growing food indoors during the winter, and making use of your home – this week I want to talk about simple structures to extend the season outside the house.  Now obviously, this won’t work the same for everyone – someone, for example, who lives in a much colder climate may not be able to overwinter anything – but they might be able to use the same techniques to get a month or two more growing season.  In other places,  you could do most of what I do outside without any of these things.  But the techniques themselves should be available for you to consider and evaluate.

 So what are some of these?  Well, the first one I can think of is mulch – yes, plain old mulch.  If you live in a cold climate, where the ground freezes, insulating the ground so that it doesn’t freeze, or doesn’t freeze as deeply can keep plants going a surprisingly long time.  Deep mulch on dormant plants marginal or not usually perennial in your climate, for example, can allow you to grow many perennial plants you didn’t think you could grow.  Eric Toensmeier grows hardy bananas in Massachusetts with deep mulch (think a bale of straw or two).  Less extreme, I’ve overwintered rosemary outside in good years and maintained a Maypop.    Figs can be overwintered with deep enough mulch (ie, enough to cover the whole plant in dormancy, wrapped well to keep the mulch on in winter winds.  Mulch is often underrated – your carrots, your beets will survive, if not a whole winter, a surprisingly long time with enough mulch.  This only works with plants that are either perennial or root crops, generally – eventually lack of light will kill everything else, but that covers a surprisingly large number of items.

Next up – the crazy easy solutions – cut the bottom off a plastic milk jug (dug out of someone’s recycling bin, of course) and put it over a favored plant.  Add a few stakes and a piece of plastic sheeting or a floating row cover, and enjoy a month’s extra time with your greens.   Stuff will also do better in sheltered spots or microclimates – that place along the edge of the driveway that is too hot for much of anything in summer will be just the spot for the stuff you want to overwinter.

There are lots of products out there to help you, including regular and fleecy row covers, cloches, and there are plenty of little greenhousey things you can buy.  These can be helpful, but make sure you are getting good quality stuff – you want heavy duty plastics designed to tolerate sunlight and snowload (if that’s relevant), and not to wear out, or row covers with long term lifespans.  Using plastics and petroleum based solutions can be acceptable, if you are getting a decent return out of them and they are the best available option – but using cheap plastics and replacing them every year is worse in many cases than transporting food from warmer places, so choose wisely.  I like the stuff sold by Johnny’s Selected Seeds for season extension.

The cold frame is a great tool, and my favorite model is the easiest to build – the hay bale cold frame.  TAke four or six or however many bales of last year’s hay or straw (that has been kept dry).  Lay out the bales in a rectangle around an existing bed, or fill them halfway up with soil and compost.  Take a window or old glass door (do not use anything that might have old lead paint on it, ever) that fits over the top, and cover it up.  Tah dah!  This kind of frame almost never overheats, because the bales don’t fit together tightly enough to prevent air from being vented, but the bales also insulate the soil well enough that things overwinter beautifully.  And in the spring, after a winter of sitting there, all the mulch is nicely decomposing and makes great organic material for your garden, and is already right where you want it.

This trick is tough if you have to put it in the front yard of your suburban neighborhood, so you might want to build a cold frame that looks prettier, like this:

You can also use a hotbed – this is a cold frame, filled with uncomposted manure, mixed with high carbon material, where the heat of composting keeps a cold frame or open bed warmer than it would be otherwise.  The composting material is covered with a layer of soil to keep the plants from being cooked, and the hotbed provides warm soil in cold times.  Because the heat of decomposition gradually declines, you will want to use this for short term, rather than long term warmth, to keep something going longer or to get a fast maturing crop ready.

There are lots of cheap greenhouse plans out there – I’ve not enough experience to know which are good, but I do have some concern with many of them in places that experience heavy snow loads – I’ve seen too many collapsed hoophouses and plastic greenhouses around here, and all are too expensive and resource intensive to be used for only one season.  This design seems sturdier than some of the cheap options I’ve seen (note, I am *not* advocating that you use their resource intensive strategy of electric heat (ugh!) and lights, just that I think the design is a bit better than some cheap options I’ve seen) but again, make sure you are doing something that will last, unless you are using all used and scavenged materials that would otherwise be landfilled.  I don’t want to see a lot of people investing time and money in new 6 mil plastic and concrete, only to waste them and their embodied energy.

If you can afford a serious greenhouse, well, I’m jealous ;-) .  There are a lot of options out there, from simple hoophouses to serious glasshouses that really do look like the Restoration era glasshouses of my dreams ;-) .  I’ll cover greenhouse options next week in a separate post.  This is about the cheap and dirty options – ones that get you a lot of food.


22 Responses to “Season Extension Techniques: Cheap and Dirty Options”

  1. risa bon 21 Jul 2009 at 11:37 am

    Umm, no, cannot do the classic greenhouse, sigh. Like you, Sharon, we do the QDOS method (Quick and Dirty Operating System, q.v.).

    In the past we got by on small lean-to greenhouses made of found materials such as sliding glass doors mounted in tandem, or fiberglass panels.

    The polytunnel currently under construction will be 10X30X7 feet, unheated, with a door, a path down the middle, and two in-ground beds. It’s almost done and has cost less than $100. Considering the price of groceries, it is money WELL spent.

    I’d link pix, but for some reason I always bomb linking to things from this comment section. :)

  2. Sarahon 21 Jul 2009 at 12:15 pm

    Do you have a south/southeast facing wall where you could put a sunspace? By making it 6′ or more deep (exterior wall of house to wall of sunspace) and as long as the wall length, you would have a lot of growing space, plus additional heat for the house.

    Mine is only 4′ deep (to keep it back from where the snow flies off the main roof) but I still have room for quite a bit of grow space; it’s just not as much as I’d like.

    The heat part is simple: an opening below and one above–I use the dog door in the basement (I have a walkout basement) and an opening in the second floor wall, simple flap valves on both. I use plastic on mine simply because I can’t afford glass but the flip side of that is that it is easy to take it off for summer to avoid overheating the house, although that’s surely not the problem this year! Most years I run a cord (hemp or other sturdy compostable) zigzag fashion between stakes in the ground and hooks on the soffit and plant scarlet runners out there to shade that side of the house. Better, and cheaper than air conditioning, and produces eats besides! In the fall I just snip the cord, pull the whole thing down, add to compost, and put up the plastic for the sunspace.

    Sarah, ~45ºN

  3. Susanon 21 Jul 2009 at 12:48 pm

    My friends Dana and Dean made a greenhouse out of salvaged windows, some recycled metal and wood framing, and recycled corrugated roofing. They have a couple of salvaged bathtubs in it filled with soil where they grew their winter crops, and the whole thing is lined with shelves floor to ceiling. They grew so many starts this year that she was selling them on craigslist. When it gets hot in the greenhouse they simply slide open the windows, and close them at night. I think you could do that with no trouble at all, especially since you already have a flat level place to build the frame.

    Now, theirs isn’t garden magazine pretty, but it is very functional (oh, and the door is an old mobile home door, they kept the entire aluminum bracket/frame setup and placed it on their frame after making sure it was level), and with just a little paint it could be fairly spectacular. Unfortunately, with them having a working farm, there’s more important things to do than just the pretty stuff.

    I am simply amazed at what people can do with salvaged stuff. I on the other hand can make stuff with salvage, but it LOOKS like salvage.

    I’ll try to find a picture to post on Flickr or something.

  4. Jennieon 21 Jul 2009 at 1:00 pm

    I too live in zone 4 and I get a LOT of mileage out of unmortered bricks topped with scavenged windows. Totally uninsulated and I can easily extend my seasons a month on each end.

  5. Jennieon 21 Jul 2009 at 1:02 pm

    Here’s a picture of my coldframe, if anyone’s interested.

  6. mgon 21 Jul 2009 at 1:28 pm

    any ideas of what to do with smaller panes of glass? We inherited about 300 panes of greenhouse glass, but only about 18″x24″ in size. all the ideas I see out there are for larger panes. Just make cold frames? Try and do a whole greenhouse???

  7. Dianeon 21 Jul 2009 at 2:04 pm

    My husband built a greenhouse window that protrudes 2′, has two casement windows on the south side and a slanting roof of double-walled acrylic. The bottom of the window starts at about knee height (it is on a wall that can’t be used for furniture) which makes it easy to tend two levels of plants.The upper shelf hangs from a rod and is acrylic on a wood frame to let more light reach the lower level. The bottom is floored in slate which we figured would add a bit of dark mass to absorb heat. The cats sure like it so it must work.

    We start seeds near the wood stove to provide warmth until they sprout, then they go in the window. We don’t use any supplemental light so sometimes (esp. this year) they get a bit spindly but usually they do okay. And it’s also the winter home of some herbs and a couple of houseplants.

    I wouldn’t say it was an easy project because, being part of the house, it had to be more carefully constructed than a free-standing and possibly short term building but it wasn’t very expensive and it is a real pleasure to use.

  8. Claireon 21 Jul 2009 at 3:34 pm

    I have a cold frame (about 10′x3′, with the front about 1′ tall and the back about 3′ tall) sitting on soil in full sun in the back yard. The frame is made from salvaged plywood and salvaged and new 2×4s, and three salvaged windows lay on top of the frame. I just planted it with seeds of bok choy, kale, lettuce, arugula, tatsoi, mustard, dill, and cilantro. I can put bricks or 1 gallon cans of water, all salvaged, in it to store a little heat. It works great in my Zone 6/7 (winter low about 0F) climate, even with gaps between the plywood and 2×4s. From late December until early February I don’t harvest out of it because the cold damages the leaves and nothing grows. It’s great for late fall/early winter and late winter/mid spring (through April) season extension. I prop open the glass when needed (by March) and by April I remove the windows and lay window screens held down by bricks over the openings. After I put in the fall crops, and until the windows get put on sometime in November, I have window screens covering the openings to keep out critters. The windows are heavy enough that they’ve never blown off – and I live in the Midwest. Nor have the screens weighted with bricks blown off. We don’t get enough snow cover to break the glass; only problem is the occasional hail breaking the glass. But we’ve got lots of extra windows. One of the benefits of living in an urban area.

    I keep our fig tree in a pot and overwinter it (November-March) in our unheated, detached garage; works great. The citrus and bananas overwinter in our unheated, dark basement (50F in January). Avocado and bay trees and rosemary overwinter in the house. Next winter I’ll overwinter the moringa trees in the basement since they went dormant in the house last winter but woke up fine in June.

    A second cold frame, same length and width but shorter, lays on an asphalt pad in back of the garage and is covered with either salvaged windows or screens depending on the weather. That’s where I start and hold seedlings. The extra heat from the sun shining on asphalt allows for tomato seeds to germinate by early April if not before, and pepper seeds to germinate by late April. I can start cool-weather crops in the frame in early March. If it gets really cold, I cover the frame with a tarp. I can start several hundred plants this way.

    I have a seed-starting setup (4 lights and a heat mat) in the basement. Because my electric use is low, however, the lights and heat mat make a noticeable contribution to the electric bill; they increase our usage by about 150-200 Kwh total over February and March when they are used. In 2010 I plan to use only the cold frame to start seeds.

    I’m reluctant to use anything plastic, maybe because I am a chemist and so I know what is involved in its manufacture. We have collected lots of windows over the years. Eventually I think we will make more cold frames with them as they work well enough in our climate and are much simpler to make than larger structures. We need replacement windows anyway due to hailstorms.

  9. Lydiaon 21 Jul 2009 at 3:56 pm

    Built myself a greenhouse (8 by 8) out of old wood wrapped single pane windows that were taken out of a house when they replaced them with vinyl ones. I framed around them and put it on cinder blocks. It has that greenhouse roofing material from the hardware store. I saved about a thousand bucks building it myself and using recycled stuff. The door is a fifteen pane door that I found on the side of the curb for free.

    I sided it with cedar singles and it looks very funky, very English garden cottage funk. I use it year round, even though winter is darn chilly. Only a couple weeks or so out of the year that get below freezing.

    it is the best thing I ever did for myself and the garden. Go for it-whatever you do.

  10. Emilyon 21 Jul 2009 at 4:06 pm

    So…I’m looking to refine my mulching technique. Last winter, I threw a whole bale of straw on top of my carrots and beets. It promptly rained, snowed, and froze, and the bale of straw (now weighing at least 75 pounds) froze to the ground. I was able to get to a few surviving roots this spring, but the crop was useless to me over the winter. Is the missing piece a cold frame on top of THAT?

    Also, my kale plants are generally 3′ tall by fall. Do you think a straw bale “corral” with some kind of cover would work?

  11. Paulaon 21 Jul 2009 at 6:31 pm

    Will each of you consider defining the terms you use the first time you use them? “overwinter” “cold frame” etc. Thanks for the good ideas, examples and instructions.

  12. Paulaon 21 Jul 2009 at 6:40 pm

    I tried to grow tomatoes this year. My plants produced, but the flesh inside the fruit looked white-ish in places —

    anybody know what was wrong?

  13. Lori Scotton 22 Jul 2009 at 2:14 am

    We have the opposite problem – in midsummer we sometimes just have to give up due to the incredibly high UV rays which plants don’t like very much, sunburn and heat on the plants.

    I have thrown my hands up and said “if you want something grown this summer, I must have a shadehouse”. Either that or just wire netting with green leaves/ grasses thrown over the top and renewed when they wilt too much.

    I guess global warming would be more pleasing to you coldies than to me.

  14. Greenpaon 22 Jul 2009 at 10:29 am

    mg “any ideas of what to do with smaller panes of glass?”

    I would try looking at older nurseries in your area- and see if any of them have an old glasshouse with small panes.

    If they do; you might go in and introduce yourselves, and offer to help tear their old house down, in return for salvage rights.

    It happens. Some years ago, a local greenhouse called me up LOOKING for someone to tear down their old house. They knew we were in the greenhouse business. The bait, in that case, was not the old glass; but the wood the building was made of. Old- original growth- cypress. Priceless stuff, impossible to get these days- and lasts forever.

    We were tempted, but couldn’t do it.

    One other comment- for beginners, I would avoid tackling too many exotic crops or growing techniques right off the bat. They take a lot of work- and are very likely to fail for a number of years.

    I’d concentrate of growing FOOD. Like potatoes, (100’s of lbs, not 10); and winter squash; and dry beans. Stuff that can keep your family alive, in real quantity. Then; when you can do that- go ahead and branch out.

  15. Christinaon 22 Jul 2009 at 4:37 pm

    Very good closing advice, Greenpa! What is the best calorie food to grow during the cold season? Are there any? Of course, I live in mild SF Bay Area, so my winter calorie crops are in higher supply… I thought I could start some August potatoes but I haven’t found a supplier; apparently most people buy out seed potatoes in the spring for the whole year? And it always surprises me that onions are considered a calorie crop!

  16. Audreyon 23 Jul 2009 at 1:10 am


    Could be lack of calcium, either due to a deficiency in your soil or not enough water to the plant. I’m guessing maybe some of the tops of the tomatoes were yellow too?


  17. Crazy Gardeneron 23 Jul 2009 at 7:03 am

    I’ve grown and harvested fresh food throughout the winter for many years now in zone 6 in Virginia (usually lows of 0 to -10). These are all cold season crops that tolerate freezing and thawing all winter (mostly greens) or being protected by mulch (root crops).

    I’ve made a very inexpensive makeshift greenhouse out of livestock panels, scrap wood, and cheap plastic. But I really hated throwing out that much plastic so often. I DON’T recommend that anyone use a greenhouse design made from PVC pipe. My version didn’t last 2 weeks before a wind storm broke all the pipes and shredded the plastic.

    Right now, most of my garden is in raised square foot beds (4′ x 4′). It is very easy to set a cold frame on top of these beds for the winter. I make the sides of my cold frames out of 2×8 wood boards, with separate flat tops out of a 2×2’s frame with 2 layers of row cover fabric stretched across and stapled on. I don’t have to worry about crops overheating with row cover, unlike glass or clear plastic covers. (However, tightly stretched row cover doesn’t like supporting more than 2-3 inches of snow!)

    For root crops, I cover them with mulch inside the cold frame and use a cover of plastic. The soil rarely freezes with this technique in my climate, and the plastic keeps the mulch dry and easy to move around for harvesting.

    I’ve been quite surprised how well the plants have survived most weather with so little protection. I’ve seen some clear corrugated sheets at Home Depot that would make nice cold frame covers, too. For larger plants like kale, I just start them late (in August) and they usually mature around 1 foot high, which I can fit in a slightly taller cold frame.

    It’s very easy to move these cold frames from bed to bed, depending on where I’m growing the fall and winter crops each year.

  18. Paulaon 23 Jul 2009 at 11:14 am

    Audrey — Thanks for commenting. My tomatoes turned red, but I don’t know that I watered enough or deeply enough. It was first attempt at growing tomatoes in raised beds. I purchased good gardening soil from a local nursery — so I don’t think the soil was poor.

    I’m about to replant for the fall. I hope to have better luck.

    Thank you again.

  19. Treeon 25 Jul 2009 at 4:57 am


    White spots just under the skin are from stinkbug damage.
    Greyish flesh inside the fruit could be grey wall-attributed to lack of potassium.


  20. Anna Marieon 28 Jul 2009 at 11:33 am

    We bought a greenhouse kit from ebay…metal framed, hardplastic windows 6×8. Two solar panels on it power a timed watering system that runs from our water barrell. I can grow greens all year, and my tomato/pepper harvest tripled, as did the basil. Best thing we ever did. Cost was £300.

    Have you tried Craigs List or ebay for a used one that you would pick up and haul away? Some friends of ours freecycled one…wood with glass. It was a monster to get the old paint scraped off and to install new glass, but they also just love it.

    Best of Luck on your quest for one.

    Anna Marie

  21. Annon 28 Jul 2009 at 5:23 pm

    There are excellent ideas for season extending in Eliot Coleman’s book Four Season Gardening. He toured his latitude in France and experiments with lots of ideas on his farm near Bar Harbor, ME. He’s been very generous with his results in all of his books. We’ve used his idea for duck housing: the Duckingham Palace. Works well. Everything he’s suggested that we’ve tried has worked well.

  22. Judyon 28 Jul 2009 at 8:00 pm

    We’re planning to construct a cold frame and were going to put it on the south face of our very old brick house – it wasn’t until reading Sharon’s essay today that it occurred to me that there might be lead in the soil there (brick has evidence of old white paint on it). Perhaps we should all THINK CAREFULLY about the history of any structure we’d like to put a cold frame next to, to avoid getting any dumber (through lead poisoning) than we already are. . . ;>) – any structure older than lead-free paint is suspect.

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