Sigma 20

Sigma 20

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.
  • Comes with two doors (one at each end).
  • Withstands a snow load of up to 3 feet (32 psf)
  • Made with a heavy-duty galvanized pipe frame and 6 mm double-wall 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.
  • Access to our private Facebook group to connect with and learn from other greenhouse owners.
Regular price $2,900 USD
Regular price $3,200 USD Save $300 Sale Sale price $2,900 USD
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Have questions? Call us 1-877-669-1286
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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.

Sigma Size
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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QualityRated 4.4 on a scale of 1 to 5
DurabilityRated 4.6 on a scale of 1 to 5
Wind and Snow ResistanceRated 4.3 on a scale of 1 to 5
InsulationRated 3.8 on a scale of 1 to 5
InstallationRated 3.3 on a scale of 1 to 5
Customer ServiceRated 4.3 on a scale of 1 to 5
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22 reviews
  • RL
    Renee Latour H.
    Verified Buyer
    I recommend this product
    Location Tennessee
    Rated 5 out of 5 stars
    5 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
    Planta Greenhouses
    5 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
    7 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
    Planta Greenhouses
    7 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
    Planta Greenhouses
    9 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


Planta Greenhouses is dedicated to deliver your order promptly, so you can begin using your greenhouse products right away.

Because greenhouses are packaged in large boxes, they have unique shipping requirements, including: 

  • We will contact you to confirm shipping price, based on your location and order size.
  • Shipping on most orders is between $250 and $450. Deliveries to remote areas may cost 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.
  • We will make every effort to ship your order in the fastest possible manner, and by the mode of transportation that you specify; however, in the event of no specific instructions, we will use our judgment and ship the best, fastest and most economical way. We are not responsible for delayed delivery due to conditions beyond our control.
  • We do not ship to PO Boxes, as in most cases you will need to sign for your item. 
  • 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. 
  • Orders placed on weekends and public holidays will be processed the next business day.


Residential Greenhouses

Are there doors on both ends of the greenhouse?

Yes! All of our Sungrow models come with manual doors and a manual window above the door on both ends of the greenhouse.

Do you have lean-to greenhouses?

Unfortunately, we do not have any lean-to greenhouses available at this time.

Do you make custom size greenhouses?

All of our products come pre-packaged by the manufacturer and can only be customized in length (6.5' extension). However, the height of the greenhouse can also be increased if placed on a base (up to 5ft above the ground)

How is the greenhouse anchored to the ground?

Every greenhouse kit comes with optional legs that can be dug directly into the ground. The amount of legs included depends on the greenhouse size.

What is the frame made of?

The greenhouse frame is made out of heavy-duty galvanized steel.

What is the width of the door opening?

For our Sungrow models, the door opening width is 800mm or 31.5".

What polycarbonate panels are used for residential greenhouses?

We use 6mm heavy-duty, double-walled polycarbonate panels with a UV-protected outside layer for our Residential Greenhouses.

What type of base/foundation is the best for me?

There are several different types of greenhouse bases, information, and pictures posted by our customers on our Customer Stories page and our Planta Facebook page. Additionally, you can learn more about "Types of Greenhouse Bases - With Pros & Cons of Each" on our blog.

Roof Ventilation Windows

Can I add windows for my greenhouse later?

Roof ventilation windows work as an add-on and can be installed only once the greenhouse installation is complete. Windows can be added later as well.

How do the Automatic Ventilation Windows work?

Our Automatic Ventilation Windows do not require any batteries or electricity. A heat-activated mechanism will open/close the window once a certain temperature is reached.

How many roof ventilation windows are recommended for the greenhouse?

It is strongly recommended to go with an even amount of roof ventilation windows. This is so you can place at least one on either side of the greenhouse. The amount of windows required depends on the greenhouse size, the climate you are in, and the types of plants that will be grown inside the greenhouse.

What are the opening and maximum opening temperatures for the Automatic Windows?

The opening temperature is between 17 °C and 25°C (62.6°F to 77°F), while the maximum opening is at 30 °C (86°F).

Sigma Greenhouses

What are the snow load and wind resistance on the Sigma models?

Sigma models can hold a snow load weight of 32 psf (160 kg / m2) or 3ft of fresh snow on top of the greenhouse. The wind resistance is 65 mp/h (100km/h).

Customization Options

Can I add my own vents, fans, heaters, and lights?

Of course! The polycarbonate is very easy to work with, and the galvanized steel frame is strong enough to support any additional accessories.

Can I get a longer greenhouse?

Most of our residential and commercial greenhouses are extendable up to 100ft. Learn more about our extension kits for both the Sungrow and Sigma models.

How can I customize my greenhouse?

The customization possibilities are truly endless with a Planta Greenhouse. To help you get started, take a look through “16 Ways to Supercharge Your Greenhouse” on our blog. 

Is hanging plants, heaters, and hammocks safe from my greenhouse frame? How much weight does it handle without affecting the guarantee?

It is safe to hang plants and accessories on a Sungrow greenhouse since each internal reinforcement arch can withstand up to 100 lbs/45.3 Kg. On the Sigma series, you can pre-drill the holes on the framing and hang small things. We would not suggest hanging anything heavier than 5 – 10 lbs / 2.2 – 4.5 Kg per arch.

May I heat my greenhouse with fire pits or similar?

You can use any heating source inside, like electricity, gas, propane, and even wood. It may be tricky to heat with wood, as you want to ensure that you keep the stove/pit away from the panels to prevent them from melting or burning if they are too close to the fire source. In this case, the customers ideally would want to come up with an exhaust system, making sure it’s not in contact with the panels, for being a flammable material.

Sigma Installation

Is there support after purchase?

Absolutely! Our after-sales customer service team is available to answer any questions and support you on your greenhouse journey. You can fill out our contact form or give us a call at 1 (877) 669-1286.

What resources are available to assist with greenhouse installation?

We offer several resources to help you with the installation process:

  1. Bilt App: Downloadable on the Apple Store and Google Play, it provides digitized step-by-step instructions.
  2. YouTube videos: A series of detailed video tutorials to guide you through the installation process.
  3. Printed Manual: Comes included with your greenhouse.
  4. Blog: Explore our blog for valuable insights such as "Expert Advice: 9 Tips For Installing Sungrow Greenhouses With Ease!"
  5. Customer-Only Facebook Group: Connect with other customers for valuable installation tips.

If you still need assistance, our customer service is ready to help via phone or email.

What type of base/foundation is the best for me?

This can vary depending on your location, gardening plans, and desired aesthetic. To better understand the different options available, you can find several different types of greenhouse bases, information, and pictures posted by Planta Greenhouse owners on our Customer Stories page and our Planta Facebook page. Additionally, you can learn more about it on our Greenhouse Bases blog.