Mini greenhouse out of scrap materials

Magic 8 Ball - February 8, 2022

AdviceGear

While spending way too much time on Reddit, I came across a project that I wanted to talk about with someone. To avoid hurting the creator’s feelings, I didn’t want to comment on the actual Reddit thread itself. It’s a great project, but there are some changes I would make.

I don’t have a sunny windowsill, so I made a mini greenhouse to start my seeds

The creator of this project used standard pane glass and scrap wood from a previous project. Cost them $10 to build.

People in the comments said that the creator needs to provide some ventilation so that the plants do not cook and the creator responds that they did put some small holes in and filled the holes with cotton so bugs don’t get in. This probably won’t provide enough ventilation.

Changes I would make:

• Place a hinge on one side so you could prop it open or easily gain access without having to remove the entire lid.
• Drill holes in the sides for ventilation and staple squares of screen window over the holes to prevent bugs.
• Add a thermometer inside to monitor temperatures. If things get too toasty I would prop open the lid or turn away from the sun. If things were not warm enough, painting the box black would absorb more warmth.
• Create 3″ feet in each corner to get the box up off the floor to prevent it from sitting in water and rotting.

Has anyone made a mini greenhouse like this before? What changes would you make to this design?

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When I do so, I start my seeds in flats inside first.  As they get bigger & it is closer to planting time, I put them outside for a week or two to harden off before planting them.  However, I rarely start my seeds anymore.  My growing season is long enough that I simply directly seed in the garden.  First in will be the cool loving plants, such as greens & peas.

 

My folks would call it a “cold frame”. I’ve made them using an old window sash and enough wood to get them up off the plants, a 2×6 or whatever you have for sides. No floor, just set the 2x6s on the dirt. Unless it is freezing cold go out in the morning and lift the lid a bit. If it gets surprisingly cold, throw a tarp over. Low tech.

Good to extend growing a bit in the fall too. Keep it simple so you can reformat as needed.

 

While I have no need for a cold frame in my neck of the woods, my favourite gardening show had a how-to a while back, using leftover materials. There was no mention of ventilation though, which I didn’t pick-up on until reading this thread. Putting a couple of gaps between bricks on the cold frame presented would probably do the trick, with flyscreen or other netting to keep bugs out if that’s your jam.

Note that the presenter lives in Tasmania, thus the comment about angling the frame North for the best sun.

 

I think those seeds, way down at the bottom of that box, are going to be shaded all day long by the walls.  A cold frame plan I once saw (I think I have it still) had a rear wall about a foot high, sloping to about 6″, which handles rain runoff nicely.

The concern about frying seedlings is real.  I just damaged some spinach seedlings that way.  The morning sun was bright, but it hadn’t yet hit 45 degrees, when I usually open the lid.  I “steamed” the edges of some of the delicate leaves by depending on outside temperature to determine when to open it.  I’d like to redesign the thing so it would open a vent automatically at a given temperature.

 

I had a greenhouse at my last house & it had the roof vents that automatically open & close with a set temperature.  They were really cool.

 

That’s a good idea to have a slope to get more sun and to deflect rain runoff. 

How would you build a automatic vent on a project of this scale? A solar powered raspberry pi with a servo motor and thermometer?

 

The mechanism is available for sale quite reasonably. It is entirely temperature operated.  No electrical parts.  It kind of looks like a hydraulic tube that may have a temperature sensitive liquid in it that expands with heat and operates the lifting mechanism.  Just a guess.

 

Even better if it doesn’t rely on electricity! 

 

Just order one from Amazon or a host of other online suppliers.

 

There is an article here on TP that links to a video of a “mini greenhouse” that simply consists of an inverted translucent Sterilite tub.

 

I’ll have to keep an eye out for that article. Certainly would be a lot cheaper and easier to just buy one of those wouldn’t it?

 

The blog article is “Beginner’s Guide to Survival Gardening” by Josh Centers.  I think it’s a very clever idea and I used part of the info in the video for starting spinach in a structure I already have.  Which are the seedlings I scorched by not venting the lid!

 

Thank you for sharing the name of the article. I found it and the related video.