Sigma 20

Sigma 20

Rated 4.6 out of 5 stars
22 Reviews

Approx Size: 10' × 19.5' × 7'

Imagine a garden filled with life yet untouched by time. A space where you can harvest heat-loving vegetables while a piercing winter storm is raging outside the door. A stable environment where vine-ripe tomatoes and succulent strawberries will thrive. A lovely quiet space to spend away from work, kids, and the chores of life.


Strong and spacious: long-lasting construction, weather-resistant materials, and roomy design.

  • Wind resistant up to 65 mph for those living in gusty climates.
  • Withstands a snow load of up to 3 feet (32 psf)
  • Made with a heavy-duty galvanized pipe frame and strong polycarbonate panels
  • Arched shape - so the wind, snow, and hail just slide off the sides.
  • Extendable beyond 100ft - so you can expand your greenhouse when you're ready.
  • Maintenance-free means you have more time to focus on your garden.
  • We offer a 5-year warranty because our greenhouse is heavy-duty and long-lasting.
Regular price $3,500 CAD
Regular price $3,800 CAD Save $300 Sale Sale price $3,500 CAD
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About Sigma 20

The Planta Sigma 20 is an urban gardener's dream come true. The quality heat-capturing materials allow for 3 or 4 season gardening, meaning you'll be able to harvest delicious fruits and vegetables beyond the outdoor growing season. Additionally, the rounded design is incredibly spacious, giving you the room to make the most out of your backyard garden.

Exact size: 118.1 x 83.9 x 236.99 inches

Feel confident knowing that the rust-resistant galvanized pipe frame is tough enough to withstand a variety of severe weather conditions – keeping your garden safe and sound throughout the year.

The greenhouse comes with:

  • two doors
  • two manual windows
  • the option to install multiple windows.

The Sigma 20 greenhouse is extremely pleasant to work in throughout the day due to the end-to-end airflow and the distinctive 7ft roof height.

Snow Load Up To 32 psf (160 kg / m²)
32 psf (160 kg / m²) is equal to 3 feet fresh snow layer or 1.5 feet packed snow layer and is maintenance free in the winter More About PSF
Wind Resistant up to 65 mph (100 km/h)
Sturdy greenhouse construction that resists winds up to 65 mph (100 km/h)
Extendable & Customizable
This greenhouse can be extended with additional expansion kits
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Rated 4.6 out of 5 stars
Based on 22 reviews
Total 5 star reviews: 16 Total 4 star reviews: 4 Total 3 star reviews: 1 Total 2 star reviews: 1 Total 1 star reviews: 0
91%would recommend this product
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22 reviews
  • RL
    Renee Latour H.
    Verified Buyer
    I recommend this product
    Location Tennessee
    Rated 5 out of 5 stars
    4 months ago
    Sigma 20’ Greenhouse

    We are loving the greenhouse. Thank you!

    Took about 7 days with 2 people to build, that’s with the learning curve and building up a level foundation.

    We chose to dig the holes and bury the legs instead of putting on concrete or 6x6’s.

    The panels had dust left inside them from the cuts from the factory and we used an air hose to remove the dust inside the panels before taping the ends. No big deal.

    It’s up and growing!

    Thank You, it’s a great purchase.

    PG Profile picture for Planta Greenhouses Canada
    Planta Greenhouses Canada
    4 months ago

    Great pictures! Your insights into the assembly process and innovative approach to foundation building are appreciated. If you ever need assistance or have more feedback, feel free to reach out. Happy growing 🌱🏡

  • MM
    Marshall M.
    Verified Buyer
    I recommend this product
    Location Oregon
    Rated 5 out of 5 stars
    6 months ago
    Got it together for Fall...

    The only issues I had were some ambiguity in the assembly diagrams. We wanted some additional internal height so we mounted it with raised foundation. Overall very pleased. Still need to fine tune the fit between the door and the window.

    PG Profile picture for Planta Greenhouses Canada
    Planta Greenhouses Canada
    6 months ago

    Thank you for your feedback. We're working on improving our instructions for a better experience. If you have any questions or need help with the door and window fit, please email us at Enjoy your greenhouse!

  • JS
    James S.
    Verified Buyer
    I recommend this product
    Location Alaska
    Rated 5 out of 5 stars
    9 months ago
    A windy place

    Although I got a late start with the gardening and was a little overwhelmed with the project. It was great to get up each morning and get out of the recliner before my second cup of coffee. Very impressed with everything about the company, your product and your people. I have placed the greenhouse on my property with a Southeast exposure, on the water in SE Alaska. The 65 mph rating gave me pause. But after the construction of the greenhouse was completed, I felt confident with a couple of modifications to bracing the unit would withstand gusts to 85mph. To say the least, I’m one happy customer!

    PG Profile picture for Planta Greenhouses Canada
    Planta Greenhouses Canada
    8 months ago

    Hi James,

    It's fantastic to know that you're enjoying your mornings surrounded by your garden. Happy gardening and enjoying your beautiful view!

  • CP
    Cheryll P.
    Verified Buyer
    I recommend this product
    Location New Jersey
    Rated 5 out of 5 stars
    1 year ago
    Love the product/ assembly is a challenge but tech support goes above and beyond

    So far I love it - we just finished putting it up - have electric to it, heat.... and soon lights. Putting the kit together was definitely a challenge - some views in the instruction manual were hard to really see and understand - so figuring it all out took time - But your customer technical service - is absolutely great - we got what felt like 24 hour support! - weekdays after work and weekends! - we even had additional videos that were shared with us - and these were very helpful - The hardware however for the doors are just falling apart - we asked for one replacement right away - but I can see we will need another already - need to consider better quality hardware - have not installed the vents yet - hoping that will not be too difficult - I would love to give more feedback once I have actually grown in it this winter and into spring -

  • KW
    Kathy W.
    Flag of Canada
    Verified Buyer
    I recommend this product
    Location Ontario
    Rated 5 out of 5 stars
    2 years ago
    The material is lightweight and strong but looks so nice

    We installed our greenhouse in 2020 & grow cucumbers, peppers, peanuts, squash, and corn. The greenhouse has extended our season by over 6 weeks and helped to grow hot climate items. The material of the greenhouse is lightweight and strong but it looks so nice. It is a great investment. We love our greenhouse.

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Sigma 20 ships in these boxes:

  L, (in) W, (in) H, (in) Weight, (lbs) Quantity
Sigma Base 1 62 11 3 46 1
Sigma Base 2 76 20 2 77 1
Sigma Polycarbonate Base 83 44 3 55 1
Sigma Extension 77 17 3 42 1
Sigma Polycarbonate Extension 83 44 2 20 2


Greenhouses are amazing products, and they require special shipping and handling. That is the reason, we have been working diligently over the past year to secure preferential shipping rates for our customers. Most shipments across Canada and the US are between $250 and $450. 

  • We will contact you to confirm shipping price, based on your location and order size.
  • Shipping on most residential greenhouse orders is between $250 and $450, customers in remote areas may need to pay extra.
  • When you place your order, please make sure to enter the correct Phone and Address at checkout. You will be contacted by phone before the item is shipped. We cannot be responsible for deliveries to incorrect addresses.
  • As part of the delivery process, we require a contactable telephone number (for the courier company to contact you) before the item is shipped.
  • White glove delivery service isn't available. The greenhouse components are delivered in multiple boxes, the largest of which weighs 80lbs. The greenhouse will be delivered to your driveway. Please make arrangements to have the package moved to its installation location. 
  • We do not ship to PO Boxes, as in most cases you will need to sign for your item.  
  • Orders placed on weekends or public holidays will not begin processing until the next business day.