Greenhouse Advice Needed

[ccfromnc]

We have a homemade greenhouse that is not working well. It is 10x13 with landscape timbers ( caulked) on the bottom 36" high then a hoop structure made with cattle panels and covered with greenhouse film. The highest point in the structure is 7-1/2 ft. Floor is bare dirt. The greenhouse door (screen door covered in greenhouse film for the winter) faces NE. A small glass window is in the back and when opened allows excess heat to escape. Fold-down shelves on both sides. There is a water hose inside for watering. An electric heater on the floor to provide heat at night.

We put in plants from our front porch and some figs and blackberries we rooted. Pretty much everything is dead and some of the porch plants look like they sunburned before freezing to death. Temp swings from very high Inside on sunny days to only 10 degrees above ambient temp at night. Granted we have had a horribly cold winter but I suspect the plants would have died anyway from the temp fluctuations.

What can we do to make this structure work to successfully start seeds and overwinter plants? We are open to anything other than torching it and starting over. Any advice would be appreciated.

[homstdr74]

Your figs and blackberries may come back---figs will often die down to the ground level then come back, but not if the ground has frozen. Which may be part of your problem---perhaps the frost has penetrated the greenhouse via the frozen soil, if it is. If that's the case you might think of digging a barrier into the soil around the base of the greenhouse.

Also, if I were you, I'd replace that flimsy door with something more substantial and, if possible, move it to some more protected side than facing north.

We had some trouble also in our 10'x20' greenhouse until we stacked some flat-black painted cans (garbage can size military civil defense cans) full of gravel on the north wall so they can get the sunlight during the day and heat the rocks up so they'll re-radiate the heat at night. Seems to be working OK now.

[TnAndy]

Do you have a min/max thermometer to check it ? Also, we have two relatively inexpensive transmitting thermometers for both our houses so we can watch the internal temps from the house.

Are you ventilating it in any way during the heat of the day ? On a bright, sunny day, it can easily hit 100-120 in a closed house. You've GOT to provide ventilation, or you will cook everything.

Our hoop house, for example, I mount a used 4' greenhouse fan in the north end, and we open the front doors (twin 3x7') to pull outside air thru it. We'll go down about 9-10am on a sunny day and at least open the doors, and flip the fan on depending on outside air temps.



What about night temps....what are they doing inside ? Holding 10 above ambient isn't enough for sensitive seedlings, or a whole lot of other things, when the outside temps fall into the teens/20's at night. You're either going to have to spend more on heating, or wait until later to start things. You can do mat heating with a cover on top, or you can use frost covers.

For example: Last night, our temps here were supposed to fall into the low 20's, which they did. We covered everything we have started/growing in our hoophouse ( strawberries, broccoli, carrots, lettuce, etc ) with at least one layer of frost blanket.....the light weight, spun fiber kind. We use no heat in that house.

The other greenhouse, is better insulated ( triple wall polycarbonate, earth berm construction ) and we provide some heat. Last night, low here was 21.....low in that house was 40. And we STILL aren't using it for warm weather seedlings yet....have some broccoli and cabbage going. Tomato seedlings (that will be set in the hoop house in another month or so) are on the kitchen counter, just at the 2 leaf stage.

Lot depends on WHAT you're trying to grow. Never grown fig, but blackberries, you could put a bed OUTSIDE, and mulch with straw/hay/sawdust, and they will come up fine when it's time for them to come up.....other wise, they would never grow in natural settings. I wouldn't waste greenhouse space or heat on them.

[TnAndy]

Originally Posted by homstdr74

Which may be part of your problem---perhaps the frost has penetrated the greenhouse via the frozen soil, if it is. If that's the case you might think of digging a barrier into the soil around the base of the greenhouse.

Yes, I'd agree. I lined the inner side of my outside wall beds with 1" of foam board.

Originally Posted by homstdr74

We had some trouble also in our 10'x20' greenhouse until we stacked some flat-black painted cans (garbage can size military civil defense cans) full of gravel on the north wall so they can get the sunlight during the day and heat the rocks up so they'll re-radiate the heat at night. Seems to be working OK now.

Good plan. Filling with water will work even better. Water will hold many more times what gravel will in heat, due to higher density. I forget the exact factor, but it's something on the order of 3-4 times better if I recall right.

[ccfromnc]

We have a transmitting thermometer but it doesn't record min/max temp, we do that visually and that's how we know that if it's 22 outside that it's around 32 in the greenhouse.

We originally (and naively) thought that we could overwinter ferns and other plants from our front porch. We now understand now that that was a mistake and our plans are to use the greenhouse only to start our seedlings.

We vent on sunny days by opening the door and the window. I see what you are saying that it may not be enough to bring the temp down when the sun is at it's highest.

Didn't even consider adding gravel to store the heat. Also, we are looking into seed mats and frost covers
... thanks for those suggestions.

[TnAndy]

Originally Posted by ccfromnc

We originally (and naively) thought that we could overwinter ferns and other plants from our front porch. We now understand now that that was a mistake and our plans are to use the greenhouse only to start our seedlings.

You probably CAN with some modifications. My wife, for example, winters her Geraniums and such over in our greenhouse ( the better insulated one ).

Here is a pic from late April one year.....you can see they did fine, and we use a very minimal amount of heat...only the very coldest nights, like sub-10 degrees or so. You can also see her tomato plants are up in the 8" range, and these will move to the garden in a few weeks. May 10th is our 'official' last frost date here ( of course, we've had KILLER frosts as late as the mid 20's of May some years ).



This is Christmas time:



You'll notice we hang a sheet over the storm door that is the entry to the greenhouse for additional insulation...also on that end piece of glass, which is single pane glass, not the triple wall polycarbonate on the front/roof. Also, you can see the 'pink' foam board on the ceiling inside ( with fiberglass batt behind it ) on the area not glazed.

What I'd do to meet what you want is add another layer of plastic on your cover, and a small greenhouse fan to keep a layer of air between the two Look in greenhouse supply catalogs...the fans are small, fairly inexpensive, and don't take much power for the amount of insulation value you get in return.

Add some insulation on the north end where you don't get sun anyway. Lowe's Home Improvement store carries a roll type foil/bubble insulation. (2',4', 6' wide x 50' long) I did that whole north wall of my hoop house in it ( the one the fan is in )....adds several R value over the plastic, AND the foil covering reflects a BUNCH of light back inside. Really nice stuff.

Few little modifications can get you 20-25 degrees over ambient temps with NO heat.

[ccfromnc]

We have some plastic drums around that could be spray painted black and filled with water. Thanks for that idea. That and foam board should help at night. We're also talking about replacing the screen door with a storm door to get less heat leaking out at night.

Omg, those plants are fabulous. My husband also thinks another layer of film could help but didn't consider using a fan in between. We're checking that out in the Grower's Supply catalog. Maybe there's hope yet that this can be functional.

[mrs whodunit]

In Canada there is a greenhouse that at night a bubble machine comes on to blow bubbles in between the 2 layers of walls. Its provides fantastic insulation. When the sun comes up the bubble machine goes off.

[jennigrey]

If it's just a hoop-house with a single layer of plastic on the outside, there's no insulation... no way to retain any of the solar heat that it accumulates during the day. The ground will hopefully be providing some heat, since the ground is warmer than the air... unless the frost has crept in from the sides, in which case it's like putting your greenhouse over a block of ice!

Adding the black barrels of water will provide a sort of thermal battery to store heat in. The black paint will absorb solar heat during the day and radiate it at night. The more thermal mass you can cram into that hoop house, the better off you'll be.

Another way to get heat in there is to compost in there.

You can make a hotbed with manure in it, to provide some heat. Small animals such as rabbits and chickens will provide some heat if they are kept in a greenhouse. Berming with soil will provide insulation as well as thermal mass (in the same way that the black barrels of water do).

If you situate the hoop house with a building against the north wall (heated or otherwise), you can nudge up the temperature a bit more. A sheet of black plastic on the north side of the hoop house will help suck up some more heat. But unless you have some place to store that heat (in water barrels, for instance), it's going to dissipate quickly when the sun goes down. Like the difference between a cloudy night or a clear night.

[mrs whodunit]

For some reason I cant imagine how a person can put a second layer of plastic up on a greenhouse. If it where wood framed I could figure that out but what about metal?

Does one need to take down the second layer in the summer?

[TnAndy]

One would attach the second layer the same one attached the first. Most metal framed greenhouses use a "U" shaped track and "wiggle wire". The plastic ( both layers ) goes in the U and the wire holds it in place.



A small fan is then attached to the inner layer of plastic and 'inflates' the space between the layers. The white plastic end in this pic is taped to the inside layer, where a hole is cut.



No, you don't take the second layer down except when you change the plastic....about 4 years. But who uses a greenhouse in the summer ?

[mrs whodunit]

Originally Posted by TnAndy

One would attach the second layer the same one attached the first. Most metal framed greenhouses use a "U" shaped track and "wiggle wire". The plastic ( both layers ) goes in the U and the wire holds it in place.



A small fan is then attached to the inner layer of plastic and 'inflates' the space between the layers. The white plastic end in this pic is taped to the inside layer, where a hole is cut.



No, you don't take the second layer down except when you change the plastic....about 4 years. But who uses a greenhouse in the summer ?

I would be the person using a greenhouse in the summer. I can grow potatoes and basil and that's about it. Frosts in July arent very conducive to growing things.

The greenhouse came with a huge fan that I will have to use to keep the temps down.

The greenhouses I have seen are metal tubes and mine is rods. Cant figure out how I would install the inner layer on either. Outside is easy but inside got me stumped. Dont really need to worry about that right now anyway. First I have got to get mine up LOL

Edited to add Oh! Now I get it. Both layers go on the same side? I always thought on layer on the ouside and one on the inside but no that nots right, is it? Hmm if thats the way it work that not very much air space.

[Callieslamb]

Can you make a tent inside the greenhouse to protect your plants? Another layer of plastic draped from the ceiling over them - or bubble wrap? You could roll it up out of the way during the day and put it back down later.

[ccfromnc]

That's what we're thinking of doing since cattle panels covered in greenhouse film would be difficult to install a second layer with a blower. TNAndy's winter greenhouse pic seems to have frost fabric draped over plants and we think that's could be part of a short term fix until we can reassess and make a more permanent solution for next fall. We're only 5 weeks from the last frost date (God willing) at this point and will be focusing on starting seeds for the garden. We do appreciate all the input so far, you've all given us a lot to think about.

[Old Vet]

Put some gravel on the flour if it is bare dirt. One layer on both sides of the roof will help. Ventilate it if at all possible with a tem switch. Water it each night.

[Harry Chickpea]

We overwinter figs in a darkened shed that has no drafts. Putting them in an area with light would just confuse them.

After my disappointment with a greenhouse, I would design something completely different than a standard greenhouse if I were to try again. I don't deny that for growers hoophouses and greenhouses work, but on a smaller scale and with less intense care, they have problems.

[Wolf mom]

Two things:

1. read everything you can get your hands on about solar greenhouses - then apply what you've gleaned to your existing structure.

2. look up Eliot Coleman's site, 4seasonfarm.com He lives in Maine & there's a wealth of info you can adapt and use in your situation.

[palm farmer]

what was humidity inside green house?

[Terri]

I have not done well with my greenhouse in the spring. I know that it can be done but I have not done well with it.

I *HAVE* had excellent results with using it as a season extender in the Fall! Last winter I ate the last of the beets in January: the tops were just a bit frost-nipped. I learned how to use the greenhouse in the Fall from Elliot Coleman's website and books. This has worked VERY well for me!

Basically, I got plants established in the ground in the greenhouse during the summer, and then I covered them with 3 layers of plastic whenever the weatherman said the night was going to be below 25 degrees.

[MOgal]

Amish farmers using hoop houses here in Missouri put a ball the size of a soccer ball between the layers of plastic in each section of their houses to provide a dead air space without dependence on electricity to run a fan.