Hot house tomatoes...

March 17, 2009

I am considering building a greenhouse in my small backyard. It wouldn't be very big, it would be about 12' x 8' or so (still considering size), and I do not plan on using it in the summer...far too expensive to keep it cool enough in the summer.

I know that I would be able to use it easily in the late winter/early spring and start seedlings, etc. I also want to use it to grow some salad veggies during the winter months (lettuce, spinach, carrots, beets, cabbage, etc.)

The biggest question I have is...Can I grow hot house tomatoes in the winter (or very late autumn/very early spring)? Is there a variety of tomato that works best? I am trying a new variety (new to me, anyway) Sub-Arctic Plenty, because it is supposed to have strong cold setting ability.

Anyone have any experience in Zone 6 (Southeast PA, specifically) with growing tomatoes in a greenhouse "out of season"?

Comments (19)

  • Mike Larkin

    How do you plan to heat it? When I first started my GH I looked into tomatoes -
    Not real sure but I beleive tomatoes needs winter temps around 60o F
    I believe you will find that it is cheaper to buy tomatoes than to grow yourself in winter
    The answer will of course depend on the total cost to heat your GH in your area for the entire winter growing season.

  • eaglesgarden

    Well, like I said, I am willing to compromise on the "WINTER" part. If I could get fresh tomatoes from it in Nov, and maybe Dec. and then tomatoes from it as early as April that would be fine. Jan/Feb/Mar tomatoes are probably not a realistic goal.

    The more important question for me is: What daytime/nighttime temp swings can tomatoes withstand and still produce fruit?

    If they can handle temps as low as mid-40s at night, and still produce fruit then I am ok with that...but if I need to keep it at 50+ at night, then I think I should just scrap that plan and simply grow roots and greens and peas.

    I am still in the very early stages of planning...nothing concrete yet...including whether the greenhouse will be freestanding or against my house. I am leaning towards next to my house to reduce heating costs of the house in winter...BUT, it might increase cooling costs for my house in summer.

    I guess I am looking for temp extremes and a variety of tomato that is more tolerant of cold/hot extremes...which may not exist! Any help is appreciated.

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  • kudzu9

    There's a reason they call them hothouse tomatoes, and you're not going to succeed with this using a free-standing greenhouse unless you're willing to spend lots of money on heating in the winter. I wanted to do this in my milder climate, but I decided $20 winter tomatoes weren't in my budget.

    If you do make it integral with your house, that changes the picture, and you should be able to significantly lessen heating costs. However, it would have to be very well-designed to work efficiently in both summer and winter, and that would likely involve some structural changes to the wall you'd build against.

  • karin_mt

    We harvested tomatoes right through November in our unheated zone 4 greenhouse last fall. The plants declined through November and certainly didn't put on any new fruit, but we were able to keep the plants going until Thanksgiving. I wrapped them up each night to keep the plants from freezing. I was amazed that we were able to keep the plants alive that late in the year.

    So I'd think that in PA you would also be able to have tomatoes in late fall.

    As for early spring, I'm just starting my tomato seeds today. But if you have a heated greenhouse your tomatoes could be well underway by now.

  • billala

    I tried tomatoes this past winter in our 12x8 Rion. Bought two cherry plants in 4" pots in Aug. 2008, and started Tomatoberry and Geronimo (Johnny's varieties) from seed in Sept. 2008, a total of seven plants. Kept the GH 58°F minimum; on sunny days it was a lot warmer than that. I heat with two 1250W electric space heaters, each controlled by a wall thermostat. On the coldest nights (22°F) they did not run anywhere near continuously.

    Here's how the plants look today:


    The cherry plants bloomed and fruit ripened until about Thanksgiving, then stopped everything until about Valentine's, when they started growing, blooming and ripening again. We have harvested a dozen or so this spring. Here's how they look today:


    The Tomatoberry and Geronimo bloomed and set some fruit until about Thanksgiving, then they too stopped everything until about Valentine's when they started growing, blooming and the fruit ripening. We've harvested some Tomatoberry, but the geronimo are just now starting to turn. Here's how they look:





  • eaglesgarden

    Thanks for the pics...

    From the sound of it, the tomatoes almost go dormant, even in a hot house, without extra lighting, in addition to the heat.


  • billala

    I suspect you're right about the light, eaglesgarden. I believe commercial growers in the upper latitudes use powerful lights. You can see in the last picture a little gro-light my wife shined on the tomatoberry fruit, but she didn't do it until about a month ago when the days were getting a lot longer anyway. I'm not going to try to put in a real lighting system - the tomatoes take up about 20% of the GH anyway.

  • elctj

    billala - how do you keep your Rion cool enough during sunny days in winter to keep from frying your plants? And what is the piece of what looks like dryer venting hose in your first picture? I have a 9' X 14' Juliana GH with 4 roof vents and use those heat-sentitive vent openers in summer, but they can't stay in during the winter - freezing with ruin them.

    And karin, you're actually starting tomato seeds in you GH in zone 4 now? I'm in zone 4 also, but in Wisconsin and we had snow less than a week ago. Are you still getting overnight freezing in your area? If so, what protection are you providing, or is a pot or cell-pack with plastic cover enough? I've got a load of flowers started from seed in my basement and I'm running out of room - I'd be tickled pink to discover that I could start sprouting in my GH this early. Your feedback would be appreciated.


  • billala

    elctj - re. cooling on sunny winter days. I have four roof vents with univent openers, and had the GH configured with doors in each end. With with a Rion Professional on a 9" base, that's a 6x7' hole in each end. I never saw the temp above 80 this past winter.

    I open and close the doors manually to control temp. The GH sits on a wood deck, and I used garden gate drop rods at the bottom of doors for better sealing. I drilled holes in the deck at intervals so I can open the doors varying amounts using the drop rods as stops.

    Door in "breeze catcher" position. Holes drilled in wood deck at various spots to permit opening door by incremental amounts.


    The dryer vent hose in the first picture is just that. Instead of a $100 greenhouse fan, I put a leftover bathroom vent fan on the floor, piping the air to the top using the dryer pipe. The fan comes on whenever one of the heaters turns on.


    Here's another view of the top of the dryer pipe.


  • elctj

    Wow billala - how clever of you. So it sounds like you use your GH year round. What is your minimum temp in the winter?

    I don't start until April - at that point I can afford to provide enough heat to maintain no lower than 50 degrees at night and I move my seedlings out there from my basement. I re-install my Univents and use a tall oscillating fan to move the air and keep it a little cooler during the day. I have doors only on one end of my GH, but they're sliders and I can open them as little or as much as I need.

    I also have another use for that fan. I've attached some drip watering line (1/4th inch) with a couple of misting heads to the wire cage surrounding the fan and have the water supply on a timer. When the water comes on the fan blows the mist around the GH and both cools and waters the plants. If I do say so myself that was a GREAT idea, and cheap!

    Thanks for your input - it's great to share ideas.

  • billala

    elctj - We do use the GH year round. Plants from Oct-Apr, pool gear & yard tools May-Sep with the shade cover installed. We have a semi-tropical climate. We usually transplant lettuce to the garden in Jan-Feb, tomatoes in late Mar, cucumbers, eggplant etc. in mid-Apr. We've been harvesting lettuce for some time, and the tomatoes are beginning to fruit. The heat finishes off our vegetable garden by early Jul. From Jul-Sep the sun is too intense and it's just too hot for the type garden we prefer.

    In a typical winter our night temps will get into the 20's & high teens for two or three nights at a time, perhaps six or seven times a winter. Cloudy day temps typically run in the 50's, & sunny days it's typically in the 60's.

  • karin_mt


    Yes, we're still having nights well below freezing. We're in the midst of a cold snap, and 2 nights ago it was 8 degrees outside, and 29 in the GH. However, the seedlings growing in the greenhouse so far are all cold-tolerant, and they spend the night on the floor of the greenhouse, with a frost blanket over them, and surrounded by black 5-gallon water buckets, which makes a reasonably warm spot for them. During the day I move them to a shelf where they can soak up the sun and warmth.

    Most of the GH space is "ground beds" where I plant directly into the ground. The perimeter of the GH is really well insulated with styrofoam sheets dug 18" deep. So the GH floor and ground stay fairly warm. Thus I've been able to grow spinach right through the winter, which is totally shocking. The plants stopped producing during the dead of winter, but then picked up again as soon as it got a bit warmer.

    My tomato seeds have not germinated yet, so they are still inside the house. Once they sprout (any day now), I'll put them on a heat mat in the GH during the day and bring them inside at night. I'm telling myself I only want to make 1 trip in and out with seedlings every day, so I'm trying to time things such that I only have 1 flat to move. We'll see how long that lasts!

    It shouldn't be long now when we'll have warm enough nights that the GH will stay well above freezing, and then I'll start more tender seedlings. As you know, the weather this time of year is so volatile! I figured if I wait until everything warms up and settles down, that's too conservative. So I'm pushing it as much as I can. This is my first full year with the GH so everything is experimental.

    BTW, on keeping the greenhouse cool in July, we've done the exact same thing as you with a home-made misting system. Works amazingly well and thus last year we had tomatoes, peppers and cukes thriving inside all through the summer.

    When I get too hot, I stand in the mist myself for a wonderful, cooling spritz!

  • elctj

    karin - Sounds like you've incorporated some pretty unique ideas to make your GH work for you in that climate. I just joined this forum recently and am amazed at the resourcefulness of people like you, billala and other dedicated gardeners. You're very daring for your first year in the GH. I can see I'm being too cautious and will have to take up your challenge - after all, the most I can lose is some seeds and I could learn a lot even from my mistakes. Even an old dog like me can learn some new tricks!

    My GH is situated among a few deciduous trees that provide enough shade to keep the temp down during hot summer, while allowing full sun to warm it and the gravel floor during the winters. That being the case I couldn't adopt your idea of "ground beds" and it's too small anyway to handle a lot of water jugs (maybe one large water tank would work). My other disadvantage is that it's too far from the house and gets snowed-in for much of the winter. I think I'll have to be satisfied with using your ideas to let me get in there earlier in Spring and extend my season in the fall.

    Have you discovered/tried the winter sowing thing? I'm taking my first try at that and am excited about the possibilities. You sow your seeds in any type of recycled container (milk jugs, take-out food cartons, etc.), you water, cover and vent it like a mini-greenhouse, place them outside and let mother nature take it's course. The seeds sprout in their own appropriate time and they're already hardened-off and ready to plant outside. One lady in the forum describes her unheated GH as a large walk-in container. So, since my inside growing space is already full and I have a lots of seeds yet to go, I'm going to experiment with this method as well.

    My husband already thinks I spend too much time with my plants and not enough with him. With all the new ideas you guys are giving me he'll really be ornery.

    Thanks much! EJ

  • karin_mt


    I agree this forum is brimming with great ideas. I did a lot of searching and reading here before we took the plunge.

    True enough that it's worth being a bit bold and trying experiments. I have lost a few things so far (including a gorgeous crop of fall lettuce that I thought I could nurse through -20 temps outside. Answer = no), but nothing terribly tragic.

    The winter sowing sounds like my kind of idea. But don't the containers freeze solid? Or does that not matter?

    As for husbands, well that's a whole 'nother topic! But actually I am pleased to report that my husband is really into the greenhouse. He's never been a garden fan until now, but he keeps a sharp eye on the greenhouse, helps out in there and is totally supportive of the whole project. I think part of this is because he helped build it so he's got ownership. Also, we're both kind of nerdy types so the experimental nature of it all has been lots of fun. Plus, he loves tomatoes, which are nearly impossible to grow here, so it's a treat to grow them so easily now.

    Billala, that's one sweet setup you've got! Thanks for sharing the photos and the info.

  • elctj

    karin - Yes, the containers can freeze and that's part of the process. However, since I'm new to winter sowing too I don't trust myself to coach someone else. Instead I'll give you the link below for instructions and urge you to try the Winter Sowing Forum - they're a fun group the loves to share their ideas and successes.

    Enjoy! EJ

    Here is a link that might be useful: Garden Web

  • bobhuber_hotamil_com

    I am looking for an outlet/catalogue to acquire a small hot house to start seeds and grow vegetables for transplanting when the weather permits. Is there a company out there that offers such an item. Want something to grow about 8 to 12 tomatoes plants, and the same amount of peppers.

  • barrie2m_(6a, central PA)

    Regarding the tomato variety question there are many varieties that are meant to be grown in greenhouses but after ten years of growing over 150 varieties in greenhouses I haven't quite figured out why the seed companies designate varieties as such. I like Big Beef as a larger tomato with good disease tolerance. I paid $300 for a M of Trust seeds a few years back and now have decided to plant less of that GH rated variety. The cherry varieties are going to produce fruit earlier- Favorita is one of the best in my opinion and worth the extra cost of seeds although I have started over 10 cherry and grape varieties for this year.

    As stated, it is not unreasonable to be able to pick fruit in late Nov.or even Dec where we are(Z6) without added heat. To get fruits in May you will need to heat on a few nights and from my experience plants will survive if you can keep them from freezing but if you want to pick from those plants up to a month earlier you need to keep your temperatures up(at least above 50F) so plants grow and set fruit optimally.

  • franktank232

    You'd have to use grow lights and lots of heat. You better look into how they do it in Canada. Its a LOT of money. Unless you have free heat (wood?) and cheap electricity to run grow lamps, then I'd skip growing in the winter months.

    I would shoot for early ripening...late April? or sometime in May. I had ripe tomatoes in June last year and that was using a non heated plastic tent! Its tough late in spring when the temps are up...i was 100F+ inside with the doors open. Need to be around a lot to spray the plants or they'll fry.

  • barrie2m_(6a, central PA)

    I wouldn't try growing early without an exhaust fan or circulation fans. These are most critical on early spring days when the sun is bright. You can bungee a sheet of plastic over the fans at night to close up the system tight but a daily routine is to uncover and flip electric switches by 9:00a in order to allow thermostatic controled exhaust fan(s) to keep plants from cooking.

    The circulation fans serve multiple purposes. They cool the plants, help with polination and dry theplants on damp mornings to help prevent foliar diseases.I wouldn't be without them. I usually rely on the exhaust fans for the first month + after planting tomatoes and then in early May I loosen sides and start rolling up sides on hot days for ventilation. My biggest complaint with the "High tunnel Diehards" is that they won't provide electric to the structures but install huge fertigation systems at a cost ten times the wiring cost.

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