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Thread: Greenhouse, Tomatoes, and temps.

  1. #1

    Question Greenhouse, Tomatoes, and temps.

    My wife and I built a greenhouse this spring (still in the process really) and put some tomato plants in it. The plants were tall and spindly while they were in the house (lack of light I'm told). Well, now they're nice and bushy, but are only now starting to show the starts of a few flowers. I'm afraid they got going too late to actually achieve any fruit before it gets too cold. I've had one day with a temp. of 88 and another with a temp. of 89. Is the greenhouse not hot enough or did we just get started too late, or maybe a combination of both.

    We don't currently have any heat in the greenhouse...Realizing we've been blessed with warmer than normal summers the last few years, is an artificial heat source something we need to look in to for the "normal" Alaskan summers? We are about the same elevation as Service High School in Anchorage, so our ambient temp. is a little lower than it is at lower elevations.

  2. #2


    Supplemental heat would help -- especially late in the summer when temps are cooling down and you are trying to "finish off" your tomatoes. If you don't have heat in the greenhouse you can always finish the plants off in the garage or in the house. I keep our thermostat at 60-65 degrees so the heater comes on at night and on cool, cloudy days. I wouldn't worry if your plants are just now starting to bloom. If it comes down to it, you can always pick the green tomatoes and bring them inside to ripen.

    Another idea is to add some grow lights to the greenhouse. I recently added a couple of cheap 4 foot shop lights and some "daylight" or "sunshine" bulbs to my greenhouse and it has really made a difference. I have a lot of basil that had 2-4 leaves for weeks and wasn't growing a bit. 1 week after adding the lights it started to take off and about 2 or 3 weeks after that my wife picked them for the first time. Our tomatoes also really got it goin' on after adding the lights. They were well worth the $30 investment.

    Good luck!

  3. #3


    We have always put composte around the outside of the greenhouse about 1-2ft high. It works great for supplimental heating. Best thing about it is that it's free.

  4. #4
    New member
    Join Date
    Nov 2008

    Default Alaska Gardening > Greenhouse, Tomatoes, and temps.

    The Right Tomato. For the typical hobby greenhouse (8x5, 8x10, 8x12), cool season "determinate" tomatoes are best. These tend to be fairly compact plants (under 4 feet tall) that do not put on lots of growth after they set fruit. Determinate tomatoes usually ripen at the same time; so, choose several tomatoes that will ripen at different times, going from seed to fruit in 50-70 days. A "Warm Greenhouse". This is one that maintains a nighttime temperature range of 55-70 degrees, preferably above 60 degrees for tomatoes. Daytime temperatures should range from 75-85 degrees. A heater, in conjunction with a thermostatically controlled vent fan, can easily provide that temperature range throughout most of California.

  5. #5
    Member COtoAK's Avatar
    Join Date
    May 2007
    North Pole, Alaska


    Huntress will have some really good advice for you on this topic as well.

    My suggestion is that you plant your toms the 2nd or 3rd week of March. No later. We usually make a little heating lamp inside and let them grow for almost 2 weeks before transporting them into bigger pots.
    After we transport them, we usually wait another 4-6 weeks until buds start.
    At this point, I would go ahead and transport them to your greenhouse.
    When you purchase your seeds, it will tell you on the back of the package. If you are located in the Interior, Holm Town Nursery is available for you and they have full charts on when to plant.
    I think that 89 degrees inside of your greenhouse might be a little high.
    Here is a good link to growing tomatoes.
    I am sure that you can probably find more on it online.

    How big of a greenhouse are you planning on making?
    Do you know what kind? A frame? Barn style?
    This year, it's our big project as well. We are going to see if we can try to get some radiant heat out to our greenhouse to warm it up.

  6. #6
    Join Date
    Apr 2006
    Riverfront Alaska

    Default Black Plastic

    I planted six tomato plants in a six by eight clear plastic green house. I put black plastic on the ground around the plants to absorb the suns heat during the day and holding that heat at night, that worked for me. Before that I would only get green tomatoes.
    If you take the woods out of the woodsman you have nothing left but a man in the woods.


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