Approx Size: 10' × 19.5' × 7'
The Planta Sigma 20 (Gen III) 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 237 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:
The Sigma 20 (Gen III) greenhouse is extremely pleasant to work in throughout the day due to the end-to-end airflow and the distinctive 7' (2.13-metre) roof height.
This is the first “real” greenhouse kit that I’ve ever owned. I was mostly able to assemble and install it by myself but there are certainly points where you need another set of hands. So far it has survived its first Ohio winter without major problems. A few thoughts:
1) the part labeling is pretty bad (the stickers fall off or don’t match what the book says), I spent a lot of time figuring out what part is what. Sometimes I assembled parts backwards so that was pretty frustrating
2) the poly panels ended up being a little wider than the greenhouse frame. This meant that I really struggled to maintain the “module spacing” to be able to properly secure the poly to the framework. You may have to rip a panel to width like I did
3) don’t skimp on anchoring your foundation into the dirt. If you live on a windy ridge top like I do you’ll want that peace of mind. I used two layers of 2x6 to make my foundation.
4) the roof vent kit is troubled. I wouldn’t put more than two in your greenhouse unless you want it to leak a lot. The chain is weak and I wish it would’ve just come with a poly panel instead of cutting one to size. The latch is my biggest issue, it is nowhere near substantial enough. But they do work and with the help of a bungee cord they’ve been holding on through Snow, ice and 40mph gusts.
5) I’m glad to hear that they upgraded the door handles and trim work. The version I have is pretty lackluster but it works okay. I used caulk, foam, tape and other gap filling…
Thank you for taking the time to share such a detailed and thoughtful review of your Sigma 20 (Gen II). We really appreciate you highlighting both the positives and areas for improvement, as this kind of feedback is incredibly valuable.
It’s great to hear that your greenhouse made it through its first Ohio winter and that you’re already seeing the benefits in temperature control and usability. That’s exactly what these structures are designed for, so it’s rewarding to hear it’s delivering on that promise.
We also appreciate your honest notes on assembly, part labeling, and panel fitment. We understand how frustrating that can be, especially on a first build, and your feedback is something we continue to share with our product team as we work on improving instructions, labeling, and overall installation experience.
Thank you as well for your detailed comments on the roof vents and hardware. Many customers choose to reinforce or customize certain elements based on their climate, especially in high-wind areas like yours, and your insight will be very helpful to others planning similar setups.
We’re glad to hear our customer support team was able to assist you along the way and that you found the final result worth the effort. That is something we always strive for.
We highly recommend joining our Facebook Community if you haven't already. It is a wonderful platform for novices to experienced Planta Greenhouse owners to share information. We have over 5000 members who share their ideas, DIYs, pictures, and real-world setups.
https://www.facebook.com/groups/plantagreenhousescommunity
Wishing you many successful growing seasons ahead!
We love our sigma greenhouse, it has kept our garden going during this winter. We installed a wood stove inside it! and the pipe did not destroy the poli! We are super happy with this greenhouse, we are planning on expanding it or buying a bigger one. I highly recommend this greenhouse, money very well invested! We live in Idaho for reference.
Thank you so much, Diana! We're thrilled to hear how well your Sigma 32 is performing through the Idaho winter. It's fantastic that you were able to install a wood stove and that the poly held up beautifully. Your experience keeping the garden going through winter is incredibly valuable feedback and will be so helpful for other growers in similar climates.
Thank you for the wonderful recommendation and for sharing how well your investment has paid off. Here's to many more successful growing seasons ahead!
The Booklet Instructions do not match the sequence of the video instructions which required rework.
I had lots of problems getting the end panel polycarbonate panels to line up properly, partly because the screw holes were correctly drilled on the bottom of the frame. The polycarbonate end panels should be installed after the doors and windows are installed.
The booklet instructions has you install the doubled-sided tape to the end of the polycarbonate panels, but the video shows installing the tape to the profile which works lot better. It should be only installed to one side of the profile which make installing much easier.
I could not get the panels on one end to line up correctly with the profile. I fought with it several hours, but it would not line up correctly. The one end fell right in place. I should have started from that end first.
The greenhouse is built very strong.
Hi Carl,
Thank you for taking the time to share your detailed feedback and for the 4-star review! We really appreciate you highlighting both the challenges you faced and the positive aspects of your Sigma Urban.
We understand how frustrating it can be when instructions don't align perfectly, and we're sorry the booklet and video sequences caused confusion and extra work during your build. Your insights about the double-sided tape application and the order of installing end panels versus doors and windows are incredibly valuable — we'll definitely pass these along to our product team for future improvements.
It sounds like you discovered some helpful techniques along the way, especially regarding the tape placement on the profile rather than the panels. These kinds of real-world insights from experienced builders like yourself help us improve the process for future customers.
We're glad to hear that despite the assembly challenges, you found the greenhouse to be built very sturdily. That's precisely what we aim for with our structures.
Thanks again for your patience during the build and for sharing your experience!
Located in mid upper Michigan, where the snow and wind can be a factor. The Sigma 20 is perfect for creating a controlled growing environment.
Think of it as a big Erector Set. It goes together easily. Just follow the instructions and you can't miss.
The staff from Planta were extremely helpful in coordinating shipping, etc. Give yourself a raise!
Thanks so much, John! We're thrilled to hear the Sigma 20 is working perfectly for your Michigan growing setup—those snowy, windy conditions are no joke! We'll definitely pass along your kind words to our team—they'll be excited to hear how helpful they were with your shipping coordination. Here's to many successful growing seasons ahead!
Beautiful greenhouse! Construction was a challenge until I used the video. The video it made a world of difference. Still working on the interior finishes it was just completed May 10th. We absolutely LOVE it!! We had 2 panels damaged in shipping and customer service was amazing! Replaced immediately.
Hi Tammy,
We’re so glad to hear you’re loving your new greenhouse — it looks like it’s off to a great start! Thanks for sharing your experience with the construction process and for the kind words about our support team. Wishing you many beautiful seasons of growing ahead! 🌿
| L, (in) | W, (in) | H, (in) | Weight, (lbs) | Quantity | |
| Sigma Base 1 | 83 | 44 | 3 | 57 | 1 |
| Sigma Base 2 | 83 | 44 | 2 | 31 | 1 |
| Sigma Polycarbonate Extension | 83 | 44 | 2 | 31 | 1 |
| Sigma Greenhouse Frame 1 | 77 | 18 | 4 | 79 | 1 |
| Sigma Greenhouse Frame 2 | 80 | 7 | 4 | 79 | 1 |
| Sigma Greenhouse Frame 3 | 77 | 18 | 4 | 84 | 1 |
| Sigma Greenhouse Extension | 77 | 17 | 3 | 73 | 1 |
| Total weight: | 434 |
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.
