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An economical greenhouse heater.

BMLBML Posts: 151
in Tools and techniques
I have several trays of seedlings and I would like to protect them in this cold snap.  At the moment I have a paraffin hurricane lamp going but it hardly raises the temperature.  I simply do not trust the adverts for such devices so I thought that its worth asking the users on this forum what they use. 
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Posts

  • Pete.8Pete.8 Posts: 11,340
    If you don't have electricity in your greenhouse then your choices are limited.
    What seedlings are they?  some varieties will succumb to a hint of frost whilst others won't mind too much.
    The only other option that springs to mind is to bring them indoors overnight if a frost is forecast.
    If you do have electricity in the greenhouse then a heat mat or heated propagator would work well.

    Billericay - Essex

    Knowledge is knowing that a tomato is a fruit.
    Wisdom is not putting it in a fruit salad.
  • BMLBML Posts: 151
    The greenhouse is next to the garage which does have electricity.  I have the following:
    A number of Dahlia corms in four inch pots just sprouting which I intend to plant out when they are larger but I'm not sure as to their susceptibility to frost and need advice.

    A tray with Dahlia seedlings about two inches high and I'm not sure as to their susceptibility to frost and need advice.

    Two trays of Tomato seedlings about one inch high which I assume are susceptable to frost.


    A tray of Marigold seedlings.


    A tray of Zinnia seeds taken from last year flowers which I have no idea if they will grow.

    A Compost bag I put a couple of seed potatoes in covering them every time they show leaf hoping they will eventually produce some potatoes.


    Many thanks.


  • Busy-LizzieBusy-Lizzie Posts: 24,043
    I had paraffin heaters too until OH arranged electricity in the GH. It has made a lot of difference. I have 3 electric propagators to start seedlings off in and an electric heating mat which is brilliant. The tomatoes are on it now. I switch it all on at night and when the weather is cold. I also have a wire in a bed of sand but I'm not convinced it's still working. It is enough to stop the GH getting frosted so I can put  slightly hardier young plants on the shelves.
    Dordogne and Norfolk. Clay in Dordogne, sandy in Norfolk.
  • Pete.8Pete.8 Posts: 11,340
    Hi BML - all the plants you mention are not hardy (with the exception of the spuds), so will all need protection from frosts.
    I use electric heated propagators (with thermostat) in my unheated greenhouse for my seeds (22c) and seedlings (18-20c) which work very well and keep them growing nicely. I usually run out of space when I start potting them up, but that's life :) then they've got 2 chances.

    Billericay - Essex

    Knowledge is knowing that a tomato is a fruit.
    Wisdom is not putting it in a fruit salad.
  • fidgetbonesfidgetbones Posts: 17,618
    I have an electric fan heater. The plug goes through an accurate thermostat, and then turns the heater on full blast when  the temp drops below 8 C. A separate max /min thermometer shows that the overall minimum has not dropped below 7.5C , so pretty effective.   As it has been a mild winter it has not been on much, but protects all my tender plants.  In my experience the thermostats on the fan heaters are not very accurate.
  • BMLBML Posts: 151
    fidgetbones many thanks for the above.  Could you give me some information on your accurate thermostat.  Also many thanks to all those who offered advice.
  • fidgetbonesfidgetbones Posts: 17,618
    This is the one I have. It works well. There are others similar available.


    I have an electric fan heater with low or high setting. I turn the thermostat right down on it, and put it on high setting, to come on and be controlled by the plug in thermostat.  My greenhouse is 12 ft by 8ft with high sides (Robinsons rosette)

  • BMLBML Posts: 151
    Many thanks.
  • Singing GardenerSinging Gardener Posts: 1,237
    I have a similar set up to @fidgetbones and would highly recommend it. I have 2 greenhouses and only heat one none but record the max and min in both and the thermostat keeps the min in the heated one at exactly the value I set.
  • Busy-LizzieBusy-Lizzie Posts: 24,043
    Are electric fan heaters expensive to run?
    Dordogne and Norfolk. Clay in Dordogne, sandy in Norfolk.
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