Winter planting in greenhouse

Discussion in 'Gardening & Plant Propagation' started by Earthbound, Oct 24, 2005.

  1. Earthbound

    Earthbound Well-Known Member

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    I'm wanting to do some winter planting in my greenhouses and was wondering if anyone has sucessfully done this? I would like to grow salad, greens , baby carrots and baby beets. i live on sothern vancouver island and the coldest day last year was -6 degrees and the cold snap lasted for about a week. Very seldom do we get snow and if so it lasts for 2 or 3 days. Average winter temp is -2 at night and +6-10 daily. I have 5 greenhouses of varying sizes smallest 8x5, and the largeat 42x32. They are all bench greenhouses so the soil on average is 3 feet deep. I will be running my chickens in 1/2 of all of them for the winter to keep the temp up and for them do do their thing(manure, bugs, weeds), all except the small one. Now every season I've just packed them in, filled with chickens and started in feb. with early vegi's before my peppers and tomato's go in, but this year i have HUGE demand for overwinter vegi's and have been offered premium dollar. What I need to produce is min 10lbs salad greens a week (i do 50lb week main season), beets and carrots, and anything else I can come up with. i grow for high end restaurants and in the winter they end up buying from a huge distributor that imports everything and they prefer local. Now I'm thinking....hmmmmmmm....I definately have the set up, and the potential ability...why not?? I have sections of some of them planted with a mixed mesclun and spinach now and am contemplating my next step.....any advice or direction would be deep down appreciated. If possible is there any way I could do it without suplimntal heat? All I have are a bunch of plug in heaters and they are expensive to run. Also what about lights? I would be making say an extra 4 bucks on 10 dollars, so 14 a pound as opposed to 10 for example so would it be worth it? I sound so stupid here, but this is new to me and I want to make sure I consider all before i comit or decline. Thanks so much
    corry
     
  2. rocket

    rocket Well-Known Member

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    I don't have any real experience with greenhouses, but they're fun to read about. Could you elaborate a bit more on what sort of set-up you have? After realizing that you were probably talking about temperatures in Celsius, it doesn't sound like it should be too tough to keep the greenhouses warm enough (since you only plan to grow cool season crops). Solviva.com might be an interesting site for you to get ideas. Aside from using chickens or rabbits to generate heat, you can try to store daytime heat to release and warm the greenhouse overnight. This might be done by circulating air through a bed of rock or a concrete wall.
     

  3. Earthbound

    Earthbound Well-Known Member

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    Thanks for the site info., looks like it will have some really good info!! My set up....Biggest one 42x32w, contrete path down the middle with 2 bench beds on either side, running the length, approx 3 feet deep with soil (which we replace every 3 years)and 10 feet wide. Aluminum dome frame, with single layer 6ml poly, probobly close to 20 feet tall.....big...
    next one, wooden frame 20x15w, raised beds, 1.5 feet deep and dirt paths, single layer 6ml poly, white washed. next, 10x5, dirt path bench beds on either side, waist high and one at the back , wood frame, single layer poly with removable shade cloth. Then the one at the house, dome shaped, pvc contruction, double layer poly with working fan, Full cemented in base ...was going to be for hydroponic lettuce, but that did'nt happen so it has no drainage at all. Floor is gravel, so we filled up 50 food grade plastic garbage bags with soil and ran them in 5 rows length wise and grew enormous tomatoes in it. Fully irrigated on a drip system to each bag and on a timer. at the front og this one we also have 2 benches 10x3 that I have the spinach and salad in now. Last one 8x5 wide, wooden benches for sarts but does have a light set up, could comfortably fit 30 flats onto both benches...I could container plant in this one.....
    What else do ya need????? I'm probobly missing some key points but it's hard to describe as I am so used to them that I don't even think about it..lol!
    thanks!! Oh all on irrigation systems except the smallest one which we hand water.
    corry
     
  4. Earthbound

    Earthbound Well-Known Member

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    On the largest greenhouse there is no gap between the plastic and the beds, there is about a 1 ft space between the ground and the frame that we block up with windows in the winter. the others have approx 8-12 inches of space.
    In regards to the beds , we have not grown anything but tomato's peppers and cillantro in the 10 foot beds, and they are planted width wise in rows with paths between, works great! We have 106 tomato plants in it this year, pruned very close to the stem and stretched up, some of the plants were over 12 feet high. We run clothsline wire across and then run a nylon "string" down to each plant and train them up these. we also had 40 or so cucumber plants and an experamental squash. I have only grown greens in the smaller 4x8 beds early and later in the season, but mostly rely on outdoor growing. I'm thinking that the braising green would work well in the big one as the plants can get quite big and I'd grow them the same, in rows with paths. The braising green are things like pac choi, giant mustards, kale, chard....
    What are your thoughts on fans and heating? Any advice on the most efficient way to heat? I know it can break you if your not careful. Only the greenhouse by the house is equipt with a fan and has the potential to be inflated between the 2 layers of plastic, but it has no drainage.....
    corry
     
  5. rocket

    rocket Well-Known Member

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    I think the most efficient way to heat is not to have any active heating at all. First of all, have you monitored the high and low temps in the greenhouses in previous winters? You've said that the outside temps range from about 20F to 50F, but the greenhouse temps will probably be higher. Next, what minimum temperature do you want to maintain in the greenhouse for your crops? Most that you've mentioned are cool season or even frost-tolerant, so I would guess that keeping the greenhouse above 35 or 40F at night would work fine. My point is that you might only need to increase the greenhouse minimum temperature by 10 degrees or less from what it already is.

    So I would start by using chickens to add heat and the stone heat-sink idea to store daytime heat. Keep track of the greenhouse daily maximum and minimum temps so you can see if you need more chickens or a bigger heat-sink. Maybe keep a heater around (propane?) to see you through until you get your passive heating methods under control.

    As for the stone (or some other material) heat-sink, the space underneath the greenhouse could work really well. You could use wood to wall off a rectangular area along the length of the greenhouse and fill it with stone (or maybe concrete blocks on their sides so the holes line up to allow air flow). Then make two holes in the greenhouse floor so you can have a fan at one end and a return vent at the other. You should also mound soil around the framed-in wall to insulate it. Picking the fan size/speed and heat-sink width will probably involve some trial and error, though.

    Okay, another question... why do you replace your soil every three years? Or is it more like potting mix?
     
  6. sylvar

    sylvar Well-Known Member

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    Its not that simple. There are several folks using livestock to heat greenhouses, but all that are successful keep the livestock in a separate area. The warm air from these areas is filtered and pumped into the growing area. The filtering is important as it removes ammonia vapor from the air that would be harmful to the plants.
    I have been doing extensive research lately on passive solar green houses. There is some good info out there, but almost all of it is based on *very* customized buildings. There is a gentleman out there...in minnisota I believe....Who does commercial winter growing in a standard large greenhouse like you have. His solution to this problem is so simple that I had one of those forehead slapping moments where you say to yourself "I should have thought of that!". He puts hoops over his grow beds and covers them with plastic. So essentially, you have a hoophouse inside a greenhouse. I will see If I can find that link. Sounds like exactly the info that you need.

    Shane