Winter gardening: cold frames and greenhouses

Wendy S. Delmater
By Wendy S. Delmater on Tue, Nov 20, 2012 - 9:03am

Here are your choices for growing things in the cold weather.


This is perhaps the priciest of the choices, but the further north you live, the more it makes sense. From Wikipedia:

A greenhouse (also called a glasshouse) is a building in which plants are grown. These structures range in size from small sheds to industrial-sized buildings...

Ventilation is one of the most important components in a successful greenhouse. If there is no proper ventilation, greenhouses and their plants can become prone to problems. The main purposes of ventilation are to regulate the temperature to the optimal level, and to ensure movement of air and thus prevent build-up of plant pathogens (such as Botrytis cinerea) that prefer still air conditions. Ventilation also ensures a supply of fresh air for photosynthesis and plant respiration, and may enable important pollinators to access the greenhouse crop. Ventilation can be achieved via use of vents.

Here are some sample greenhouse projects and suppliers.

Here's a design similar to what I used last winter. May I warn you from experience that you do NOT want your plants touching the plastic?

And here's a good book on the subject: Backyard Greenhouse Plans, by Bill Keane

Cold Frame:

A miniature greenhouse is known as a cold frame. East to make, inexpensive, and big on results, a cold frame may keep you in fresh produce all winter. Cold frames are typically set on the south side of the yard, in full sun, and it's a good idea to have them up against the wall of your heated home, even though they mostly use solar heat. Make the back about 12 inches higher than the front. During sunny days the sash can be propped open with a stick to prevent sunburning the plants. If the sun is bright, temperatures in a cold frame can reach 85 degrees Fahrenheit even when the temperature outside is freezing. Close the frame at night and during cold weather to protect young plants.

From Wikipedia:

A traditional (cold frame) plan makes use of old glass windows: a wooden frame is built, about one to two feet tall, and the window placed on top. The roof is often sloped towards the winter sun to capture more light, and to improve runoff of water, and hinged for easy access. Clear plastic, rigid or sheeting, can be used in place of glass. An electric heating cable, available for this purpose, can be placed in the soil to provide additional heat.

Here are some sample cold frame projects and suppliers.

Grow Indoors:

Not everything needs to grow outside. From fresh herbs on a windowsill to an indoor Meyer lemon tree, when it comes to houseplants, this bud's for your table. Choose compact, miniature, or dwarf varieties of crops and crops that are quick maturing. Small, quick-growing crops will require less space and time to reach harvest. Grow lights are an option, but have a large energy cost. Hydroponics can be done small-scale indoors, too!

Finally, don't forget that an indoor sunroom can act as a greenhouse. Yes, I know - we're talking about an extension on your home. Not cheap. But if you're in a position to add a sunroom to your permanent northern home, it can provide passive solar heating plus a great place to grow that Meyer lemon or other fruit trees.


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Wendy S. Delmater
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kickstarter project: tabletop aquaponics

The inventor is using crowdfunding to try and get this into production. Looks pretty cool. .

So what's happening?

  • The fish, they poo and they pee, and all that waste-water gets broken down by beneficial bacteria into nutrients
  • The waste-water from the fish is then pumped up & upcycled as organic fertilizer for the plants. The plants take up the nutrients and, at the same time, clean the water which then falls back down for the fish.
  • There is no soil - the plants are growing just on rocks - all the nutrients coming from the fish (no need for any artificial fertilizers - it's all organic.)
  •  There is no need to clean the water because of the plants - it's a self-cleaning fish tank.

What Can You Grow?

Choose from a variety of fresh produce, including spinach, baby greens, oregano, beans, basil, mint, parsley & thyme. Full article here.

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Hoop green house designs-DIY

Anyone build a greenhouse themselves using a PVC-hoop design?  I have time, but not much money.....


I am living in Virgina where lows can go into the teens in mid winter.  I'm expecting that nothing will grow under these conditions, but it would be nice to extend my growing season late into the fall.



Thanks for any thoughts

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Snowload and Wind?

sand_puppy - Does your location have any significant winds or snow to deal with?  I will be building a cattle-panel greenhouse in the next month (7'x20' (4 panels)) and estimate it will cost me about $200.  I will be buying the 4 year reinforced UV greenhouse plastic to spread the cost over multiple years.  From past experience of using the cheaper 6 mil plastic from Home Depot, the sun and cold ruins the covering in less than a year and it becomes very brittle.  Then you have a huge mess once the plastic gives way to wind, rain and snow. Little tiny pieces of plastic blowing through the garden.  

Here is a WSID article on greenhouse types that might give you some more insight:

and here is an article on coldframes and other season extenders that can be really low cost and give you the ability to grow lots more in colder climates:

Hope this helps and let us know if you have any other questions.



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Greenhouse designs

Thanks for your thoughts and articles on greenhouses, Jason.  We do have some wind and an occasional foot of snowfall here in central Virginia.  What does a cattle panel green house look like?  Any plans available on the internet?  I greatly appreciate your advice about the "4 year UV greenhouse plastic" which will outlast the cheaper 6 mil Home Depot type.

Any known plans for a DIY geodesic greenhouse design?  This looks like the most sturdy and weather resistant, (but expensive).  I will be putting it in my front yard in a residential neighborhood and an attractive, well-made structure might fly better with the neighbors.



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Cattle Panel Greenhouse examples

Here are a few examples of CP greenhouses.

Some of the things I plan on doing with my design are to:

- Use a split piece of PVC pipe to cap the ends of the CP to prevent rips and use greenhouse film clips to secure the ends.;ft1_canopies_tents-ft1_clears...

- Design the north side of the structure for spring starts and propagation with benches and the south facing side as production beds.  (it is going to get really tight with such a small space. 

- Front and Back walls will be designed for accommodation of a center ridge beam to allow for hanging baskets and pots. 

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Hoop house

Here is a link to a design that we described a while back.  It has worked out fairly well for us.  After the first year, I got some greenhouse plastic sheeting, which has better light transmission, but is more expensive.

The design has withstood several heavy snows and moderate hurricanes, including Sandy here in northern Delaware.  I made several 2X4 braces from the center rail down to the ground to provide support for snow load.

See the post by JRB near the bottom of the page.


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Hoop Green House design

Thank you so much Jim.  Very nicely done by the way.


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Yoopertopia growing system

Cold weather growing system from the Upper Peninsula of Michigan.

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Mike K
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Glass or plastic?

Hi all,

I live in South East Queensland, Australia and whilst we rarely even get a frost and have relatively mild winters I would like to extend the growing season of my plants. I have had some solid metal tube frames made up which I use to attach a white shade cloth in an attempt to protect the plants from insects however I have yet to come up with something to attach to the frame to create a greenhouse for the cooler months? I am always thinking about high quality and for the longer term (may not be easy to replace down the road?). So I wondered if anyone could advise whether glass is better than plastic for longevity? I know some plastic can be UV treated however that still wouldnt last as long as glass (unless glass is physically broken?).

Also, I understand the benefits of UVB radiation on human skin as it forms Vitamin D (if you dont know just how special and important adequate vitamin D is you need to investigate! No one is going to advertise its benefits as it is free from the sun so there is no money to be made!). I also am aware that UVB does not penetrate glass or plastic so I am wondering if plants need UVB as much as we do? Probably not I suspect but would be interested to hear from someone who may know?

Not holding my breathe that these questions will be answered but thought I would throw it out there and see...


Mike K

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