Growing season extended by how much in zone 4/5?

welhamMarch 26, 2007

How much longer will my growing season be with a 4-mm twin wall opaque polycarbonate panel greenhouse? I am in Montreal Zone 4B/5A.



This is the greenhouse I am considering

Thank you for reporting this comment. Undo

Before you spend $1,000.00 on that one, if you have or can find the means to spend more- check out the following .

Then check out the insulation values between 4 and 6 ml. If you could go with the BC, as a bonus, you would get a far higher quality structure, with some real working space, a roof line that not only looks elegant but by virtue of its design, sheds snow long before the weight of a really heavy fall could make the least impression on it, and perhaps the best bonus of all for a neophyte; one of your country's most shining examples of truly outstanding, personal, customer service via an 800# or email.

But you would have to make your decision quickly to take advantage of both the sale price and the free shipping.

As for season extension, I can only say that from my own brief experience with my own GH; fall extension lasts well past the first frost. I held quite a few annuals over until the first really hard freeze with no supplimental heat at all. However, an unheated GH placed directly on the ground will enter early spring with frozen ground beneath it. So if you are looking to jump start spring and start seedlings in late February or very early March, the better you ground insulate, the cheaper it will be to add supplimental heat and in your latitude, without a very well sealed GH and ground insulation, the cost of fuel to run supplimental heating just as you most want to use your GH, could be ruinous.

Whatever your final decision, I truly believe it is a serious error to buy any GH based on any accessories that may come with it. Start with the very best quality structure you can afford and work from there, even if it takes a few seasons to finally get it all fitted out.

    Bookmark   March 26, 2007 at 7:55PM
Thank you for reporting this comment. Undo

birdwidow - I would love to be able to buy that greenhouse but even the costco one would be stretching my budget. I don't really care about accessories like shelving because I can easily build my own. I'm just looking for the best thing for my zone under $1000.


    Bookmark   March 26, 2007 at 11:14PM
Thank you for reporting this comment. Undo

I lived in zone 4 in Alaska. A few times, I grew all year long. It cost me an arm and a leg. Providing heat was easy, costly, but easy. The hardest part was providing enough light during the winter. It just wasn't there. You can extend the season as much as you want as long as you're willing to pay for it. A reasonable extension would be about a month on each end without too much cost. A cheap thin-walled greenhouse like that one, just isn't built for anything more than that. Sorry, I have to agree with birdwidow.

    Bookmark   March 27, 2007 at 2:27AM
Thank you for reporting this comment. Undo

In some of the other posts I've read - people are using bubble wrap on the inside of the GH to add better insultion during the fall winter an early spring. Bubble wrap is inexpensive, goes on an off the panel easily and rolls up for storage. I'm just finishing my GH project and plan on trying the bubble wrap idea. Comes in small, medium an large bubble. Check out the link below.

Here is a link that might be useful: Bubble wrap

    Bookmark   March 27, 2007 at 8:23AM
Thank you for reporting this comment. Undo

Assuming you orient your GH roof axis east-west you could also make a big difference with conserving heat even with the $1000 GH by completely insulating the north wall and north facing roof in the fall with rigid insulation. The end opposite the door could also be covered in the late fall because it will receive negligible amounts of light in the northern states/canada. And if you are really up to it, cover the greenhouse completely at night with blanket, tarp, etc.. anything to add an extra layer on to conserve heat loss.

As far as extra lighting, I have seen custom built large greenhouses that have a reflective shutter above the south facing panes. The winter sun reflects off of the shutters and increased light 140%. Not possible with that GH but thought I'd throw it out..

    Bookmark   March 29, 2007 at 6:31PM
Thank you for reporting this comment. Undo

Bonjour Lakshmi

I live at Carignan, 20 minutes of South of Montreal. I saw at costo the greenhouse in question and I think than you can utilize without extra heater from april 1th until last of october. I'have a BC Grennhouse 12 x 20 you can see the photos on my web site


    Bookmark   March 30, 2007 at 12:08PM
Thank you for reporting this comment. Undo

Hi Michel,

Thanks - That was exactly what I wanted to know! :-)

You have a beautiful collection of day lilies. Do you only ship or can people vist and buy? My Aunt would love it!


    Bookmark   March 30, 2007 at 12:29PM
Thank you for reporting this comment. Undo


We have an open garden the last two weekends of July
You are welcome


    Bookmark   March 31, 2007 at 8:30AM
Thank you for reporting this comment. Undo

I do think you can extend the growing season beyond the last frost, the trouble is, the light just isn't there..the days shorten and the amount of light needed to mature say tomatoes and peppers just isn't available..

And in the spring, you fight the frost issue so much you just have to have some kind of heat source to keep all of the seedlings warm at night, that is if you raise palnts from seeds like i do..

I want to know the temperrature inside that greenhouse all the time so have several probes that i can read in the have to keep of top of the temperature at all times if you want success..

I think i have 8 or 10 ml twinwall and the temp will be a good 60 plus in there on a winter day if the sun is out..besides, with all the uv protection, it is a nice light inside the gh..

I would go with the highest grade of twinwall i could possible afford as that is where the protection from the elements lies..

Forget the shelves and all the other cute accessories that you can buy..that will come with time..


    Bookmark   April 9, 2007 at 9:53PM
Sign Up to comment
More Discussions
GH Tomatoes - 2015
Yeah!! We opened our GH this week for the 2015 season....
Photo--Jim's chic shack
Not quite finished yet, but thought that I’d share...
James_Shaw_San Francisco Bay Area
Convertible/Multipurpose Green House. Is this a good or bad idea?
I want to have a multipurpose enclosure around my backyard...
Subterranean Heating/Cooling System - Continued
This is to continue the discussion from the previous...
My green house is still winterized. Every possible...
Hans P. Gruetzenbach
Sponsored Products
Hammaka Universal Hammock Stand with Blue/White Pillow Hammock Combo - 40731-KP
$449.98 | Hayneedle
DaVinci Emily 4-in-1 Convertible Crib with Toddler Rail
Sunny Health Fitness Magnetic Recumbent Bike - SF-RB921
$159.43 | Hayneedle
Black stripe bin
Origin Crafts
Tulip Watering Can Flower Pot
$22.99 | zulily
Windflowers Burgundy 40-Bulb & Pruner Set
$18.99 | zulily
Design Toscano Sir Sagremors Dragon Sculpture with Glass Gazing Orb - NG30854
$197.95 | Hayneedle
Live Ground Cover Rose Red Ribbons - Set of Three
$19.99 | zulily
People viewed this after searching for:
© 2015 Houzz Inc. Houzz® The new way to design your home™