Wednesday, January 16, 2013

Mobile Greenhouse - Ready for Plants

Tuesday evening the greenhouse was deemed ready to go into the real world, actually my backyard.  I wheeled it from the pole barn to it’s location behind the beds.  It was not hard to move, although a little awkard.  It was set north of the raised beds and faced toward the south.  I leveled it some with scrap wood.  It looks like a solar panel teetering at the edge of the pond, although the shoreline is about 40 feet away. 

The pond doubled in size over the weekend.  Before last weekend it was at it’s lowest level ever, about 5 feet below the overflow, thanks to the epic drought we had last summer.   When it got warm for a few days the 15 inches of snow on the ground quickly melted, and then we got 4 inches of rain to add to the runoff.  In a few days the pond rose to the overflow and probably doubled its surface area.  Sure looks better. 
This morning I filled up the one earthbox I have with potting mix and planted it with lettuce.  I was going to leave the earthbox in the house until the lettuce germinated but decided to just go ahead and put it in the greenhouse.  That’s a limestone block at the front of the bench left over from last year's landscaping.  It's there for thermal mass and weighs about 60 pounds.  I’ll put some more blocks in there later but they are still frozen together right now.  (For those of you who don’t live in the midwest it’s not uncommon to get huge temperature swings from day to day as weather systems from every direction push through this part of the country).  The little wood box in front of the planter holds a remote sensor so I can monitor the temperature inside.  I wanted to make sure it was not exposed to direct sun so I can get accurate readings.
It’s a partly cloudy day with the sun peaking through now and then.   At noon the temperature was about 30 degrees F while inside the greenhouse the temperature was 55 degrees F.   By 1 PM it looks like the temperature inside the greenhouse has leveled off at 60 degrees, with a little more cloud cover now.  It looks like it is working, in fact I’ll have to watch out for overheating on warmer, sunnier days.  
I noticed that the earthbox walls have gotten quite warm and that will heat up the soil inside it.  It’s going to take a few days to warm up all the stone once it is inside the greenhouse.  I’m hoping this thermal mass will release enough heat at night to keep the water in the earthbox reservoir from freezing.  This spring I plan to put several flats of onion seedlings in the greenhouse so they get the natural day length.  And of course it will be used as a cold frame to harden off plants. 
There’s still a few changes I plan to make when I build the next greenhouse.  It’s a little bit tippy, although the weight of the stone inside makes it more stable.  I’ll probably angle the back wall a little on the next one to give it a little wider stance.  And there’s still some issues to work out with the door props and some other things.  But it’s finished enough to give it a real world test and I’m looking forward to getting an early crop of lettuce.      

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