Sigma 26

Sigma 26

Approx Size: 10' × 26' × 7'

Bring the tropical heat of the Caribbean to your own backyard in the middle of winter. Enjoy your own micro-climate where you can grow sweet new fruits and flavorful vegetables beyond the limitations of the weather outdoors — a space where you can harvest, snack, or sit and feel wonderful among your plants.


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 $3,550 USD
Regular price $3,950 USD Save $400 Sale Sale price $3,550 USD
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Have questions? Call us 1-877-669-1286
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About Sigma 26

The Sigma 26 was designed with a focus on spaciousness and stability. This greenhouse is perfect for 3 or 4 seasons of growing, allowing you to harvest fresh fruits and vegetables well into the colder months. Our Sigma greenhouses are built to last, featuring a rounded design and creative construction that brings heavy-duty greenhouse engineering into your own backyard.

Exact size: 118.1 x 83.9 x 315.79 inches

The end-to-end airflow, spacious size, and high 7ft roof height make this a comfortable place to garden throughout the day.

The greenhouse comes with:

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

The galvanized pipe frame is both rust-resistant and durable. In addition, the construction can withstand moderate to extreme weather conditions, ensuring your garden will stay safe and flourish throughout the seasons.

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 4.9 out of 5 stars
Based on 12 reviews
Total 5 star reviews: 11 Total 4 star reviews: 1 Total 3 star reviews: 0 Total 2 star reviews: 0 Total 1 star reviews: 0
100%would recommend this product
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QualityRated 5.0 on a scale of 1 to 5
DurabilityRated 5.0 on a scale of 1 to 5
Wind and Snow ResistanceRated 5.0 on a scale of 1 to 5
InsulationRated 4.3 on a scale of 1 to 5
InstallationRated 3.7 on a scale of 1 to 5
Customer ServiceRated 4.3 on a scale of 1 to 5
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12 reviews
  • CP
    Chester P.
    Verified Buyer
    I recommend this product
    Location Pennsylvania
    Rated 5 out of 5 stars
    10 months ago
    Sigma 26 Pennsylvania

    My wife loves it. The two of us put it up together in October, it took about three 8 hour days but one day was partly getting the ground ready. Pretty easy if you just follow the videos online. Installed the self opening windows this spring and everything is working great. Couldn’t be happier. Highly recommend

    PG Profile picture for Planta Greenhouses
    Planta Greenhouses
    10 months ago

    Thank you for sharing your experience! It's wonderful to hear that you and your wife are enjoying the greenhouse. We appreciate the recommendation. Happy gardening! 🌿🏡

  • KW
    Kay W.
    Verified Buyer
    I recommend this product
    Rated 5 out of 5 stars
    10 months ago
    Thanks Planta greenhouse!

    I really appreciate having the greenhouse. It was a challenge to assemble, but very rewarding after completion. I planted from seeds and within 3 days, radish had popped up and within 1 week cucumber also came up from seeds. Now everything is growing with gusto and I have received so many compliments on the greenhouse. It has only been finished for 2 weeks and it's the end of August 2023. Thanks Planta greenhouse!

    PG Profile picture for Planta Greenhouses
    Planta Greenhouses
    10 months ago

    Hi Kay, we're delighted to hear that your greenhouse is thriving and that you've received compliments on it. 🌱🏡😊

  • CU
    Candasa U.
    Verified Buyer
    I recommend this product
    Location New York
    Rated 4 out of 5 stars
    11 months ago
    Mostly positive.

    A handle was set for the wrong side and the tape for sealing does not stick well.

    PG Profile picture for Planta Greenhouses
    Planta Greenhouses
    11 months ago

    Hi Candasa, thank you for your feedback.

    We apologize for the inconvenience you've experienced. If you need any further assistance, please contact our customer service at We're here to assist you and ensure your satisfaction.

  • DK
    Dmitriy K.
    Verified Buyer
    I recommend this product
    Location Maine
    Rated 5 out of 5 stars
    1 year ago
    sigma 26

    Great product. Little cumbersome to assemble.. compensated by good customer service.

    If you looking for good green house , you will not be disappointed.

    Result for 1st year: cucumbers- July to October too many. Eggplant -about 50 lbs. Sweet pepper 2 buckets.

  • KM
    Kevin M.
    Flag of United States
    Verified Buyer
    I recommend this product
    Location Arizona
    Rated 5 out of 5 stars
    2 years ago
    The stability of the greenhouse is really good even in the wind

    We installed our greenhouse in 2021 and right now we are starting the new garden for 2022, so we’re growing seeds and other plans that can’t handle the cold. I believe it will add to the times we can grow. With the heater we bought with the greenhouse we should be able to grow year round. The stability of the greenhouse is really good even in the wind. And we had snow just this week (February) and it is holding up perfectly.

    My buying experience from Planta was good. It was challenging but rewarding to work through the instructions and also follow online video instructions for putting the greenhouse together. I’d recommend using both the paper manuals and online step by step videos when putting it together. If possible, have more than one person to construct the greenhouse. I was able to do it by myself but I’m sure it took quite a bit longer.

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Sigma 26 ships in these boxes:

  L, (in) W, (in) H, (in) Weight, (lbs) Quantity
Sigma Base 1 62 11 3 46 1
Sigma Base 2 77 23 3 92 1
Sigma Polycarbonate Base 83 44 3 55 1
Sigma Extension 77 17 3 58 2
Sigma Polycarbonate Extension 83 44 2 20 3


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).

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.

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.