I have a very long term stretch-goal of being able to produce enough plants to fully meet my families nutrition needs. I'm in Auckland, New Zealand - equivalent to USA hardiness zone 9b.

I'm aware there are lots of variables, but can anyone provide insights/suggestions on how large a hothouse I would need, assuming that all my winter vegetables were going to be grown in it ? (For example, I'm aware of a "rule of thumb" that says you want a minimum of 1000sqm land / person - but, of-course, this applies to land not hothouse space)

I don't want to use hydroponics, just regular growing in soil, possibly with some heating to say 54f.

  • 1
    Davidgo, I've been taken to the 'wood shed' again, grins! Please tell us more about your needs and circumstances. 1000 sq. ft. per person I've not seen but makes sense sorta. Definitely different in a green house. Less room for mistakes! My 10,000 sq. foot vegey garden produced enough food for 10 people...I am not liking their 'qualifications'...is that for an entire year? What zone...? That kind of thing. I agree, you do not want to do hydroponics. I've never tried because all I can see are huge headaches. I'm working on my 6th greenhouse to be heated this next year.
    – stormy
    Dec 4 '16 at 19:49
  • Check out rocket heaters for your greenhouse. Propane is wonderful as long as you can get refills. Tanks of propane last a good while and the CO2 is beloved by your plants. But we are designing a rocket heater which runs on any biomass you have hanging around, heats the soil because you run the energy out through your garden buried just shallowly well, we are you don't have to put it out under the soil. I'm putting ours out under the walkways.
    – stormy
    Dec 4 '16 at 20:06
  • In zone 9(b or not) I doubt you'd "need" a hothouse at all. Want is different. Eliot Coleman manages with cold frames and unheated hoop-houses (look for "4 season harvest" at a library) - in zone 3/4.
    – Ecnerwal
    Dec 6 '16 at 2:50
  • @Ecnerwal - you are right, my question probably came out wrong. I know you can subsistence farm in zone 9 without a hothouse, but I specifically want to grow everything in a hothouse so I can build a system/model which is fairly automated (built on all the things I wanted but can't have in the commercial hothouse I gave up). Also, tomatos, eggplants, cucumbers don't handle the winter frosts.
    – davidgo
    Dec 6 '16 at 4:16
  • Rob does a great aquaponic system, and feeds his family from it: facebook.com/Bitsouttheback/?fref=ts Dec 12 '16 at 6:34

My favorite garden was in zone 5, 100 X 100 with perfect silty loam soil. No need for a hothouse/greenhouse. Plenty for a family of 4, fills a nice 10X10 pantry with root crops/canned vegeys/dehydrated/frozen plus enough to give friends, the food bank. Had perennials like asparagus, horseradish, raspberries, boysenberries, strawberries and artichokes.

Now I've got a greenhouse of 1200 Sq. ft. Zone 1b, seriously insane. My soil had to have yards of decomposed organic matter added. Every month of the growing season has had a freeze or two. We still had an awful lot of produce and preserved vegeys. And we haven't heated the greenhouse for the past 4 winters. Next year, finally (rocket heater). Perennials such as herbs, strawberries, vine berries, Asparagus (takes 3 years before you can harvest), raspberries, blue berries. Are you doing a poly hoop green house or a kit or dimensional lumber?

We use the soil beneath the greenhouse as a garden with raised beds (1' high 3 or 5' across, 3'main walk, 1' walkways between the beds, 3' beds all around the periphery), trenches for drainage and have a few crops in pots like tomatoes, peppers lining the main walkway. We have a little heated green house for producing all our starts earlier and to drag all the potted stuff inside at night (argghhhh). I don't do straight lines of vegeys, I make use of every square inch. Broadcast or 'sheet farming'. Way more production. Plenty of room for rotation every year. Cover crops in between cash crops. Worth the time and effort. Is your greenhouse visible from the road?

There is one book you should buy as well as others but make sure you read Shane Smith's Green House Gardening!

  • 1
    does this answer the question?
    – J. Musser
    Dec 3 '16 at 11:30
  • There is no way jose anyone can put a size on a greenhouse that will work without knowing, type of soil, zone stuff, their proficiency, do they want to be able to use this year round, what is it they think they want to grow. I simply added sizes to an outdoor garden in a proper zone and proper soil and the size we've now got in a very inhospitable area for soil and climate. Obviously they've got an area in mind. Shane Smith's Greenhouse Gardening will help them even further. Just trying to help them think things through for their own individual needs. Or ask clearer more specific question
    – stormy
    Dec 3 '16 at 21:28
  • And lucky me, this OP actually asked for INSIGHTS. Which is what I tried to give them to start a conversation. This Question/Answer thing for OUR site or black and white or making things so simple just doesn't work. Wouldn't it be a good thing to call a MEETING to get our heads together to redesign all of this to be more helpful, especially when people don't know the correct questions to ask and obviously need more than a simple answer or what they can get off the internet by themselves. Yes? No?
    – stormy
    Dec 3 '16 at 21:32
  • 1
    that's what forums are for, and there are already quite a few out there .
    – J. Musser
    Dec 3 '16 at 21:41
  • I am not sure what you are trying to teach me J.!! Grins.
    – stormy
    Dec 4 '16 at 8:52

The most accurate way to answer this question is to attend a local farmer's market. Talk to the greenhouse growers that grow the vegetables you want to grow, and get some idea of their productivity.

You may or may not need artificial lighting if wanting to grow tomatoes in winter.

Greens will still grow in winter, they just take longer when it's colder, and more likely you won't need to heat the greenhouse if just growing greens. However, some Asian greens tend to bolt if it gets too cold. You can keep them warmer then outside temperatures with another layer of plastic. See Elliot Coleman's book on the subject, the winter harvest handbook.

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