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Greenhouse heating

I have a small shop in an indoor market, among other things I sell plants. I have an account with a couple of nurseries but with the price of fuel it isn't profitable for me to travel distances for stock, therefore I have sourced some very good local amateur growers which enables me to provide plants, flower and veg at affordable prices  to get to my point, some things I grow myself, particularly tomato varieties like tumbling tom and Shirley  but, and here's the rub, I need to get the seeds in during February in my very small, non glass, greenhouse, so the subject of heat comes up as I have no power supply to my garden. I have a paraffin heater, but cost of paraffin horrendous, plus fumes would kill Tom plants. I do, however, have a pot bellied wood burner and wonder if it would be worthwhile my taking it into the greenhouse and using a smokeless fuel like volcano rock or similar, to get heat up to 20 degrees for germination. Sorry its so long! What do you think, or any ideas?



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  • JennyJJennyJ DoncasterPosts: 7,706
    I don't know about the stove, but could you germinate the seeds on a windowsill indoors, maybe with a heated propagator base, then move them to the greenhouse once they've got their first true leaves and been moved into individual pots? Then you wouldn't need such a high temperature in your greenhouse. Maybe do it in batches - customers without greenhouses won't want to buy plants until May or even later depending on where you are, while those with greenhouses will want them earlier.
  • Its bad enough keeping an insulated house at 20 degrees I suspect that keeping a greenhouse at that temperature would be like tipping money down the drain, getting seeds to germinate in a heated propagator indoors would be a fraction of the cost but then you face the problem of low light levels during February so would need to use grow lights. I have raised tomato plants in a well insulated unheated greenhouse even with overnight frosts the plants don't seem to mind the cold so much once they are growing well as long as they don't get frosted and get enough light. Good luck I hope you find a solution. 
  • JennyJJennyJ DoncasterPosts: 7,706
    I agree, the fuel to collect them from another nursery would probably cost less than heating a greenhouse to tomato-germinating temperatures. I don't know what sort of scale you're talking about though - dozens, hundreds, thousands? You'll need space to keep them at least frost-free until you sell them.
  • Thanks guys, I'm talking 100's. Unfortunately my kitchen, although large isn't suitable because of light issues. I do have a large amount of bubble wrap and think maybe insulation is the key.
  • Pete.8Pete.8 Billericay, EssexPosts: 9,869
    Unless you can balance any additional heat with stronger light I fear you'll end up with 100's of very leggy (and therefore useless) seedlings.
    Bubblewrap over the windows will only reduce the light further.
    LED lights are cheapish to run, but they need electricity.

    Many of us have tried sowing tomatoes in Jan/Feb and found it just doesn't work.
    I have a heated propagator in an unheated greenhouse.
    Early in the year the propagator (150w) just can't keep the temps up to 20-22C.
    When the seeds germinate, the light is still so weak and brief that they grow long and thin in search of good light and end up collapsing under the weight of their seed leaves.

    I now start mine in late Feb/early March, then by the time they've germinated the days are lengthening and sunlight is much stronger and I have no problems.
    They are good sturdy plants and grow fast.
    Knowledge is knowing that a tomato is a fruit.
    Wisdom is not putting it in a fruit salad.
  • SherwoodArrowSherwoodArrow Nottinghamshire Posts: 196
    edited November 2022
    I’d also have issues with putting a fire in a non glass (I assume plastic) green house with plastic bubble wrap inside, you might end up with temperatures reaching higher than 20C!🔥 
  • JennyJJennyJ DoncasterPosts: 7,706
    I start my tomatoes around end of March/beginning of April. Any earlier and they're ready to plant out (outside, no greenhouse here) before the weather is ready for them.
  • It would either be bubble wrap or heater, not both. I may leave until later, they always catch up. Thanks for your comments guys. Guess it depends on the type of winter we get.
  • Thanks Pete.8. I think that's what I'll do.
  • Pete.8Pete.8 Billericay, EssexPosts: 9,869
    Good luck Patricia
    I've found seed sown in early Spring will soon catch up and outperform seed sown earlier as they get off to a much better start.

    If you're looking for an early ripening tomato, I usually pick the first Stupice and Rosella at end of June/early July in the greenhouse. Stupice will go on until October too.
    Knowledge is knowing that a tomato is a fruit.
    Wisdom is not putting it in a fruit salad.
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