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do mini pvc greenhouses actually work?

londonTiger Posts: 4,903 Forumite
I know that they will trap heat when it's sunny and all that, but what about during night time, there is no sun to produce heat obviously, but do they actually retain any heat at all? I would think that it would quickly drop to atmosphere temperature as soon as the sun stops beaming direct sunlight onto the mini greenhouse.

Also how does that affect plants? Is it any more effective than say using pot plants, keeping them in the house overnight and putting them back out during the day?


  • lawrie28
    lawrie28 Posts: 2,666 Forumite
    Xmas Saver!
    Not the biggest expert, but yes they do.

    They don't retain much heat at night, but then a glass greenhouse doesn't either.

    Seeing as people have been growing in greenhouses for years, I don't think it bothers plants.

    moving them in and out the house will work with some plants, but takes time, and for larger plants could be cumbersome. It also limits the size of the planter to what you can carry without damaging the plant..

    The biggest risk to plants in the Mini greenhouses is them blowing or being knocked over if they are not secured properly.
  • wellused
    wellused Posts: 1,678 Forumite
    I have one of the really cheap £20 ones from Argos it has three shelves and a zip up door, I have had it for about 3 years or so and for the past two years I have taken geranium cuttings and potted them up in this greenhouse with very good results. The greenhouse is situated at the bottom of the garden where it gets the most sun and although it has three shelves the bottom one is taken up with a bag of ballast to prevent the whole thing from blowing away, this is essential although if I needed the bottom shelf I'm sure that there are other methods of achieving this stability. When the temperature falls too low during the winter months I relocate my greenhouse to the protection of my carport which has the benefit of having a clear plastic sheeted roof and is situated in between two house walls and a garage door only open at one end. The geranium cutting remain in here over winter although if the temperatures are forecast to fall very low I either move the cuttings indoors or wrap the greenhouse in a layer of fleece or bubble wrap. During the really cold nights this year when it got as low as minus 6 or 8 degrees I did lose a few of the cuttings so I moved the rest temporarily indoors to be safe. In the spring when the sun got back on the bottom of my garden I moved the greenhouse back outside, since then the geranium cuttings have grown into plants and have been joined a few weeks back by some African Violet seedlings grown indoors from seed. Just to be on the safe side I wrap a layer of fleece around the greenhouse at night and during the nights when it was forecast that the temperatures would drop below freezing I have also added a plastic tarpaulin which I remove in the morning. So far the plants have all grown in this greenhouse and are looking healthy, I do have to open the zipped door during the day though as if I don't the interior steams up and will lead to fungus growth on the plants.
  • culpepper
    culpepper Posts: 4,076 Forumite
    The ones we had were not bad.
    We had lettuce in them till about october and they do help when you don't have a lot of windowsill space for seedlings.
    I think the one we have now(polycarb) is probably a little bit warmer in the early and late part of the year(maybe one month warmer either end).
    I'm not a scientist but I spose plants don't photosynthesise at night and so maybe not working hard to do so means they can better stand the cold of night time.
  • faerie~spangles
    My little greenhouse is situated in my brick 3 sided bin bay, it fits perfectly. Gets the full midday sun which of course heats the brick.
    I'm not that way reclined

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  • poppysarah
    poppysarah Posts: 11,522 Forumite
    Think of them as a raincoat not a house.

    They will shelter plants from rain and wind, but not temperature... And if the wind gets too much it'll whip the thing away too.
  • wellused
    wellused Posts: 1,678 Forumite
    Just paid £19 for one from Wilkinsons this morning it's bigger than my original but the plastic sheeting is a bit thinner gauge, I should get loads of plants in it and free up the spare bedroom of seedlings too.:T
  • Sylje
    Sylje Posts: 7 Forumite
    I fastened my new pvc green house down with tent pegs over the metal bars at the bottom and into the spaces between paving stones - last autumn. Also it did have some ballast from the bags of soil on one shelf during the winter, but these are now being used in the garden. My brother did tell me I should have waited until spring to put it up, but it has survived! There are geraniums, ageratum, fuschias and lobelia growing well in there - all of those are scheduled for hanging baskets for me and my Mum and Dad, with leftovers into the garden. One geranium has already gone into the garden as it started to flower, and I've brought the 3 patio buddleias outdoors as their lower leaves have started to yellow - not sure why? Possible they need potting on, though I've done that once, or maybe feeding?

    My worst problem is that I will take the tiny plug plants out of the plastic box in which they arrive before reading the instructions, (which tells me not to do that!) and have ended up not knowing which colour any of them are going to be :o I like a surprise though, and nature seems to combine all sorts of colours quite successfully. I did start the tiniest seedlings off on the window ledge indoors, as they arrived really early and very small. Most, thankfully, have survived.

    I'm not great at killing pests, think everything deserves a life so once the spare plants are out in the garden they will be slug and snail fodder! Hopefully the ones in the hanging baskets won't get eaten, though I have found snails clinging to the outside of my upstairs windows before now. I think I may invest in some grit, or something like that, to put round the base of the plants to help keep them away. One or two snails did get into the greenhouse, the sneaky devils, and munched a few leaves. I relocated them outside, and further away!
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