Mini Greenhouse questions

[Roberta]

I'm assuming that you can run power to that GH. You might find that seedling heat mats under plants will give enough warmth to get them through the night and they are waterproof. (Problem with a space heater is keeping it dry, unless designed for a greenhouse... electricity and water don't play nicely together.) Water in the morning, so that things are dry by evening - a dry orchid can tolerate a lot more cold that a wet one. Open it up by day to keep temperature from going too high and facilitate air flow. If it too bright, Aluminet shade cloth (made with aluminized mylar, available online) reflects heat as well as blocking light (and also will reflect interior heat back in at night) . Phals probably need to stay indoors - they really don't like to go much below 60 deg F. But a lot of other orchids (Catts, especially the mini-Catts, Oncindinae, cool-growing Vandas like Neofinetia falcata and its hybrids, etc) can tolerate the big temperature swings and cold nights. So be selective about what you put out there, try a few things before you commit your whole collection...

[Dollythehun]

Just my For the money and effort you are putting into this structure, you could build your own unit. We once had to sink short landscape timbers in the ground, drill them, and bend conduit, inserted into timbers, to house a clients plants. We covered it with shade cloth but, you could use a heavy plastic from Lowe's. You get the picture...

[SouthPark]

Definitely - keeping the temperature within safe levels and suitable levels is important in any growing area. And getting sorted out (manual and/or auto control) of the temperatures in a green-house will take effort and time and money. For auto systems, reliability is going to be important, especially in very hot and/or very cold places.

[mildwhiskers]

I can't run power to the greenhouse, at least not for the time being. I've also tested the temperature and humidity inside the greenhouse with the door rolled up, and it still heated up to high 80°-85°F/26°-29°C. Having fans might solve that issue though. I have heard the suggestion to buy small solar powered fans, since the greenhouse is small and doesn't need anything too big or fancy. Does this sound like a good idea and if so, any recommendations on what to buy?

Originally Posted by Roberta

If it too bright, Aluminet shade cloth (made with aluminized mylar, available online) reflects heat as well as blocking light (and also will reflect interior heat back in at night) .

Would I put this over the plastic on the greenhouse or would the plastic need to be removed entirely?

Originally Posted by Dollythehun

For the money and effort you are putting into this structure, you could build your own unit.

As much as I'd like to build my own set up, I can't because my family is renting, so we can't build any permanent structures in the backyard. And I got my greenhouse from my grandma as a Christmas gift, so it hasn't been exactly a money investment I will be saving money for fans and such though.

I know I can't put all my orchids into the greenhouse, like the phals and paphs that have been doing well inside, but my oncidiums, catts, dendrobiums and other orchids could use more light and humidity than what they are currently getting inside.

[Roberta]

Originally Posted by mildwhiskers

Would I put this over the plastic on the greenhouse or would the plastic need to be removed entirely?

You can just put the shade cloth over the plastic. You can either rig some sort of support (you can do all sort of tinkertoy stuff with PVC pipe, cheap and the connectors are easy to find at your favorite big-box home improvement store) (As with the GH, securing against wind is important)

The solar-powered fans may be worth a try. Just opening it up during the day will help the heat buildup too. High 80's F is not enough to hurt plants, you don't want to go too much higher. Again, shade cloth will help - the ambient temperature is less of a problem than "hot spots" from direct sun. The shade cloth (maybe 50%) just evens out the light and therefore the heat. Another thought with regard to getting a little heat in there... a couple of black 5-gallon buckets filled with water - they'll heat up in the sun during the day, and radiate that heat during the night. (Again, low cost, Home Depot or equivalent)

[Diane56Victor]

Computer fans might work for you. I think they are quite cheap and small so wont be taking up too precious space.

[mildwhiskers]

Interesting, I'll definitely give the shade cloth and the buckets a try! I think I'll hold off on buying the fans until the shade cloth gets put up, if that and having the door up provides enough air circulation then I may not need them (at least until summer).

The only other concern I have is humidity. Would the black buckets double for providing humidity in the greenhouse during the day? Even with spraying the floor in the morning, the humidity still drops to around 30%.

[Roberta]

Originally Posted by mildwhiskers

Interesting, I'll definitely give the shade cloth and the buckets a try! I think I'll hold off on buying the fans until the shade cloth gets put up, if that and having the door up provides enough air circulation then I may not need them (at least until summer).

The only other concern I have is humidity. Would the black buckets double for providing humidity in the greenhouse during the day? Even with spraying the floor in the morning, the humidity still drops to around 30%.

I think, keep a lid on the buckets... they are just heat sinks. (I don't think you want a mosquito farm) As long as the medium of the plants holds moisture, and you water when they are dry, I doubt that ambient humidity is a problem for most orchids. It's that dry for only a few hours most of the time... when the temperature drops the humidity rises. The occasional dry windy period won't hurt... my collection lives mostly outside and when those dry winds blow (caled Santa Ana, Diablo, Sundowner depending on where you are) I get humidity into single digits and even the pleuothallids survive (I just increase the watering when that happens). Basically, in California rain and humidity come out of the end of a hose most of the time. Fact of life.

[ArronOB]

Thinking about those mini greenhouses.

If I was going to use one such as the OP posted, then based on several years experience with them then these are the mods I would make before going forward.

1. Add a second roll-up door made of shadecloth, fixed just above the current plastic film roll-up door. On winter nights, the plastic film door is rolled down. The rest of the time the shadecloth door is down. You need the shadecloth door down to prevent sunburn, but allow maximum ventilation. The shadecloth door is held down with strips of Velcro, and has weights sewn into the bottom. This is necessary to prevent the door from being blown aside and allowing sunburn, which has happened to my plants once or twice.

2. Cut a window in the rear, and sew some shadecloth into it. Retain the plastic film covering, as you will need to close this up on winter nights. The reason you need this window is because moving air will not flow efficiently into a confined space unless it has some way to flow out. Naturally you want the window on the rear wall so it is as far from the door as possible.

3. Cut some vents in the top - right at the very apex. Again, sew shadecloth panels into these vents to prevent sunburn. And again it would probably be best if you can retain the original plastic film so you can close these in winter. The reason for this is because hot air rises, and overheated air will collect under the roof. I left mine closed one unexpectedly hot morning in early spring and cooked the plants on the top shelves.

I realise this is quite a bit of work. I made my first couple of shadecloth covers as slipons on an industrial sewing machine and it was time consuming, but for the last one I just bought a bag of zip ties, rolled the shadecloth over, fixed it with zip ties and cut the excess off - quick and easy.

Further points. Be careful with the use of fans - if you are not effectively venting the hot air then they will simply dry-roast your plants.

Likewise, I did many experiments with heat sinks (water, rock and sand) and was never able to achieve a measurable effect. The basic problem is that the walls provide so little insulation. My mind is not closed on that, our winter is coming and I would be happy to hear from those who have experienced a measurable difference.

[mildwhiskers]

The main issue with cutting windows in the plastic I see is that there's no way to reinforce the corners of the plastic to keep them from ripping. I also don't feel I have the skills or equipment to make those cuts without messing it up (at least right now). Since I just got this greenhouse, I don't want to make any major cuts to it that I can't fix, but I greatly appreciate the ideas

Also looking at the picture of the greenhouse on that site, I should've mentioned that, for mine anyway, it has two small windows, one on either side of the greenhouse. They have their own plastic flaps that can be put up and they have a white netting to keep bugs out (I imagine). The instructions that my greenhouse came with don't show those windows for some reason either, so that would be a good thing to check for those who are looking to get this greenhouse.

I haven't really noticed too much of a difference in temperature with them both open, and I don't really feel any breeze coming through them either. But I've kept them open, figuring that they might be bringing in some fresh air throughout the day.