What is a Martha Tent / What is the Martha Tek?
The term Martha Tent was born out of the underground mushroom community and is used to define a mid-sized grow chamber that allows you to contain an effective controlled environment for fruiting mushrooms in trays, blocks, and jars.
Martha Tents can fit inside any closet, kitchen, or basement, or be scaled up to fruit pounds of edible or medicinal mushrooms for consistent harvests every week. Their potential is unmatched as they can be altered to fit any space or budget requirement.
We created this comprehensive Martha tent set up and maintenance guide to help anyone interested in learning Martha tek or the Martha technique for mushroom growing. It includes step-by-step instructions for building a Martha setup, setting up and dialing in environmental controls (humidity, air flow, gas exchange, and spore filtration) and includes a troubleshooting guide for identifying potential issues with your grow.
What is a Martha Tent / What is Martha Tek?
The term "Martha Tent" was born out of the underground mushroom community and is used to define a mid-sized grow chamber that allows you to contain an effective controlled environment for fruiting mushrooms in trays, blocks, and jars.
Martha Tents can fit inside most closets, kitchens, and basements. They can easily be scaled up to fruit pounds of edible or medicinal mushrooms for consistent harvests every week. Their potential is unmatched as they can be altered to fit any space or budget requirement.
Martha setups are the surest way to grow consistent and beautiful flushes of mushrooms year-round. All in all, they’re a solid solution for beginner to intermediate mushroom growers working for a variety of species, growing techniques, spaces and budgets.
The following is our complete step-by-step process to building and maintaining your own Martha Tent, using materials you can find online or at your local hardware or hydroponic store.
Marthas are the surest way to grow consistent and beautiful flushes of mushrooms year-round. All in all, they’re a solid solution for beginner to intermediate mushroom growers working for a variety of species, growing techniques, spaces and budgets.
The following is our complete step-by-step process to building and maintaining your own Martha Tent, using materials you can find online or at your local hardware or hydroponic store.
How to Build a Martha Tent
Martha Tents are one of the most effective ways to fruit mushrooms indoors. Search any mushroom forum, Reddit page, or Facebook group and you'll find dozens of versions of Martha Tent builds few to none that are exactly identical. Although Martha Tents may come in all shapes and sizes, those who have found success in growing mushrooms attribute it to the ability to balance four conditions: humidity, fresh air exchange, temperature, and light.
Martha Tents control two of these conditions: humidity and fresh air exchange (for exhausting carbon dioxide), while the environment outside of the tent determines the temperature and light conditions. All in all, it’s a balancing act that only works if all four conditions are balanced and the environmental systems of your tent are working in tandem.
- Humidity: Mushrooms will dry out or not fruit at all if the environment is too dry. Therefore, humidity is dispensed and monitored by your humidifier and humidity controller to maintain a proper moisture content inside the Martha Tent.
- Fresh Air Exchange: Like humans, mushrooms inhale oxygen and exhale carbon dioxide. Meaning, if the air inside the tent isn’t constantly refreshed, they may suffocate. Excess carbon dioxide is exhausted by our fresh air exchange fan, allowing oxygen to freely circulate throughout the tent.
- Temperature: Most mushrooms fruit well in temperatures between 55-80 degrees Fahrenheit. It’s recommended to place your tent in a temperature controlled environment. Some builds will utilize heating pads or heated water humidifiers when the ambient temperatures of your tent’s environment are cooler than 55 degrees Fahrenheit.
- Light: Unlike plants, mushrooms don’t photosynthesize. However, they still require some ambient light in order to fruit properly. By placing your tent in an area with indirect light or supplemental lighting, it will help your mushrooms determine where to fruit and the color of their fruit bodies.
If you manage all four of these conditions properly, you will have beautiful mushrooms in no time.
- Greenhouse Tent
- Fresh Air Exchange Fan
- Ultra-Sonic Humidifier
- Humidity Controller
- Hose Clamp
- Poly Pre-Filter cut down to size
- Drip Tray
- 4 inch Ducting
- Foam (cut to fit a window)
Step One: Build the Tent
The first step is to build your greenhouse tent. Ideally, you’ll want to use a greenhouse tent that has five shelves; if this isn’t the case, we suggest you remove the bottom shelf and place it at the top. If you decide to do this, you’ll want to reinforce the bottom of your tent to maintain its structural integrity. (Although we decided to use a transparent tent, some growers may opt to use an opaque stealth tent. Opaque tents work just as well as long as you install supplemental lighting at the end of the building process.)
There are a few reasons why we prefer to create extra shelf space at the top.
- It allows you to maximize the total grow space inside your tent
- It creates space at the bottom for your humidifier
- And lastly, your fresh air exchange fan will sit at the top, which will help pull humidity through the tent and exhaust CO2.
Once you’ve finished building your greenhouse tent, you’ll want to place it on top of a drip tray. This drip tray will help seal and capture any excess moisture. If you aren’t able to find a drip tray, you can simply use a folded tarp and clamps as an alternative.
Step Two: Install the Humidification System
The next step is to install your humidification system. You’ll need both your ultrasonic humidifier and the humidity controller, which will be used to monitor and control the ambient humidity inside the Martha Tent.
The ultrasonic humidifier will be placed at the bottom of the tent, with the electrical wires threaded underneath the bottom of the greenhouse plastic. Make sure that any electrical component is not sitting in the drip tray where it is more likely to have direct contact with water. Pro tip: Make sure to not place any mushrooms in the direct line of the humidifier if you decide to use the bottom shelf. This will ensure that your mushrooms are not oversaturated with water, and that the humidity is dispersed evenly throughout the tent.
Once you’ve placed your humidifier at the bottom of the tent, you can open up your humidity controller and position the sensor on the top shelf. Ideally, with the sensor slightly to the side so it’s not directly in line of the humidifier’s fog. This ensures a more accurate reading of the average humidity range inside of your tent. Make sure to thread the wire down the back of the tent and underneath the greenhouse plastic.
Lastly, place the humidity controller outside of the tent, plugging in the humidifier and the sensor into the controller.
Follow the specific instructions of your humidity controller for usage.
Start by setting the low range of humidity to 70% (meaning the humidification system will turn on when humidity drops to that level) and a high range of 90% (meaning the system will turn off when it hits 90%). This will make the average humidity around 85% which works well for the majority of grows. Make adjustments as needed if your mushrooms are showing signs of being either too dry or too wet. We’ll go over the symptoms of both conditions at the end of this article.
Alternatively, you may see some growers use an external humidification system that looks something like this:
This is a DIY humidification system that uses a pond fogger to generate humidity inside of the bin, while a computer fan pushes the humidity through a duct and into the tent. To make this system, cut two holes into the lid of a Tupperware bin with one hole sized to fit a computer fan and the other sized to fit 4 inch ducting. Position the computer fan to be pushing air into the bin. Attach both the ducting and fan to the lid with duct tape. The pond fogger should have a float ring that allows it to sit on top of the water inside of the bin. Thread the power cord out through the top and plug it into an outlet. You will need to cut an additional 3.5-4 inch hole into your greenhouse plastic near the bottom of the tent. Thread your 4 inch ducting through the hole and secure it with duct tape.
Although this system does work, there are a few drawbacks.
Though this system provides a large reservoir for water, pond foggers aren’t particularly reliable and tend to have fairly short lifespans. For this reason, we like to use the ultrasonic humidifier and refill it more often. This is up to your own personal preference.
Step Three: Install the Fresh Air Exchange Fan
The third step is to install your fresh air exchange fan. Because you’re exhausting air out of your tent, you’ll be making what is called a negative pressure system. This means you’ll be making a vacuum inside the tent. In a positive pressure system you’d be pushing fresh air into the tent causing it to balloon outwards, but this comes with the downside of losing the ability to direct spores and moisture out of a duct or through a filter.
Though you’ll see positive pressure builds elsewhere on the internet, we prefer negative pressure systems for a few reasons:
- You’re able to exhaust spores and CO2 outside of the tent
- As the air is filtered through the fresh air exchange fan, oxygen rich air is pulled in from the bottom of the tent
Simply place your fan on the top shelf, with the exhaust end facing the back of the tent. Run the wires down the back underneath the bottom of the greenhouse plastic.
Since you’ll be altering your tent to grow mushrooms, you’ll need to cut a hole in the back of the tent that’s big enough to fit your fan, but small enough to create a tight seal. Trace the inside of your fresh air exchange fan on the plastic of the tent with a sharpie, and then cut it out with some scissors.
Once you create an opening for your fan, gently guide your fan through the opening. At this point, your fresh air exchange fan should be able to balance upright on the top shelf.
The last step is to attach a filter to the back of your fresh air exchange fan to capture any excess spores so that they don’t permeate your living spaces. You can use a 4 inch hose clamp to attach your filter to the back.
Once you’ve attached the filter, you now have a fully functioning Martha Tent. Although this build works great inside closed spaces without access to a window, you can also choose to duct your spores outside a window if one is available using flex foil ducting.
Step Four (optional): Duct from a Window
Using ducting to exhaust the air outside of your Martha Tent is a good idea when there is a window available and your tent is placed in a home or living space. This is also a good idea for people who may be sensitive to spores or particulates in the air.
Building a duct is fairly simple. By placing your Martha Tent near a window (out of direct sunlight), you can attach a 4 inch duct to the back of the fresh air exchange fan, and seat the end of the duct through a fitted piece of foam. Be sure to remove any filters prior to installation.
And voila! You’ve finished building your very own Martha Tent!
Placement of The Martha Tent
As we discussed earlier, mushrooms rely on the fine balance between: fresh air exchange, humidity, temperature, and light.
In some ways, the dynamic interaction between these conditions are what make mushroom growing a blend of art and science.
In the video tutorial, we placed our tent in a climate controlled out-building away from direct sunlight. Our spores and CO2 were ducted outside with the fresh air exchange fan - and our humidification system will maintained proper moisture content inside of our tent.
The placement of your tent may vary depending on your set-up, but this set-up can be replicated in a multitude of ways with a few minor adjustments.
Fresh Air Exchange
- Just like humans, mushrooms inhale oxygen and exhale carbon dioxide.
- Since the Martha Tent is a sealed environment, without proper fresh air exchange carbon dioxide may build up inside your tent and suffocate your mushrooms.
- Installing a fresh air exchange fan allows you to exhaust excess CO2 and maintain proper levels of oxygen.
If you place trays of colonized mushroom mycelium inside of a closed tent without any alterations or fans for air exchange, your mushrooms would eventually suffocate due to high CO2 and lack of oxygen. This is because just like humans, mushrooms inhale oxygen while exhaling CO2.
Without constantly refreshing the air in the tent, the exhaled CO2 will build up and disrupt the mushroom growing process. This is why we installed our fresh air exchange fan. You can also use a carbon dioxide meter to get precise measurements of CO2 concentrations, though this isn’t necessary as long as you keep an eye on your mushroom growth, acknowledge symptoms of high CO2 (lack of growth, leggy stems, or coral like growth), and adjust accordingly.
In the wild, lower levels of CO2 help indicate where a mushroom should fruit. Inside your grow tent, an abundance of fresh air will have the same effect. Just having great air exchange won’t guarantee beautiful flushes of mushrooms though. Without a system for managing ambient humidity your mushrooms will eventually turn brown, crack, or dry out due to overly dry air.
- Humidity ranges between 70-90%, depending on the species you're growing.
- Mushrooms may dry out or never grow if the environment lacks proper humidity.
- Conversely, mushrooms that are oversaturated with humidity may become soggy or have fuzzy stems.
Humidity is the next condition managed by your Martha Tent that influences mushroom growth.
Mushrooms are about 92% water, and for this reason, mycelium in the wild will wait until rainfall or humid conditions to produce mushrooms. So, along with a fresh air exchange fan, mushroom growers will add humidification systems in their tent in order to prevent mushrooms from drying out or not growing at all.
Fresh air exchange and humidity systems are the two primary components you’ll add to your Martha Tent. But, you’ll still have to account for the ambient conditions outside of your tent.
- Most mushrooms grow well between the temperature range of 55-80 degrees Fahrenheit.
Even with a fully built Martha Tent, most growers place their tents in areas that have some form of climate control. Regardless of the location you’ll want some control over the temperature surrounding your growing environment.
Under natural conditions, many mushrooms will fruit in response to seasonality, limiting the time period in which mushrooms grow. Growing mushrooms indoors year-round requires more consistent conditions.
Your tent should be placed in an environment that generally stays between 55-80 degrees Fahrenheit. Though keep in mind that the exact range tends to vary between mushroom species.
- Unlike plants, mushrooms don’t use light as an energy source. Though, they do need some light in order to determine where they will fruit and develop colorful fruit bodies.
- The smallest amount of light will work, whether it’s indirect light from a window or artificial.
- It’s generally advised to not place mushrooms in direct sun as it may raise the substrate, or growing chamber, to harmful temperatures.
Unlike plants, mushrooms don’t use light as an energy source to grow. But mushrooms are photosensitive; meaning the smallest amount of light helps determine the shape and color of the mushroom fruit bodies. Light can also trigger mushroom growth or indicate suitable fruiting environments. On the flipside, too much direct sunlight can cause your mushrooms to dry out or make it harder to control your other conditions.
Growers who place their Martha Tents in environments that lack light, such as a closet, will use supplemental lighting. Growers who place their tents in open living spaces will generally position it in an area away from direct sunlight.
So, fresh air exchange, humidity, temperature, and light are the four conditions of mushroom growing. By balancing all four, you can fruit beautiful flushes of mushrooms year round.
The best way to manage and adjust the conditions in your Martha Tent, is to observe how your mushrooms grow over time.
High CO2 Levels
If you have skinny stems, or fruit bodies, or growth resembling coral, it could be because the carbon dioxide levels are too high.
Excessive CO2 or Moisture
If you have fuzzy stems, the cause could be excessive carbon dioxide or moisture.
Low Humidity or Harvest Late
If your caps are brown or cracked, it could be that there’s not enough humidity or that they were harvested too late.
High Temperature or Low Lighting
If the fruiting bodies are pale, it could be because of a high temperature or because of a low light environment.
High CO2 Levels, High Temperatures, Too Dry, or Substrate Was Not Fully Colonized
If there was no growth at all, it could be because of high carbon dioxide, high temperatures, or because your substrate wasn’t fully colonized, or because your substrate was too dry.
Low or Temporary Drop in Humidity
If your growth stopped after pinning, it could be due to low humidity, or a temporary drop in the humidity.
31 Replies to "How to Make a Martha Tent Mushroom Fruiting Chamber"
Very a great post. I simply stumbled upon your blog and wanted to say that I have really enjoyed browsing your blog posts. After all, I’ll be subscribing to your feed and I am hoping you write again very soon!
Theresa we can help get you growing at email@example.com, a photo would be great!
Daniel we can help more if you reach out to firstname.lastname@example.org! If you want to include a picture too that helps us better troubleshoot (:
To the northspore.com administrator, Your posts are always informative and well-explained.
Can I put a plastic bag over the box of Lion Mane mushrooms that I was given at Christmas in order to keep it humid? I live in Utah which is a dry environment.
I will put the mushrooms in a 65 F basement room with a small light.
My tent arrived yesterday and it is now set up! Looking forward to the electrical portion of the tent so I can inoculate my substrate and start growing!
We have the BoomRoom set up and growing pink oyster and lions main perfectly from the fruiting block kit. However we have also put the Maitake Grain spawn (layered with sterile hardwood substrate) on the top shelves of the Boom Room. It is growing something but more like Mold?!?? Help! May be I can send you pics to help diagnose the problem?
Rudy, we have spawn you can experiment and try! You can email us at email@example.com for more information.
Can I grow morel mushrooms in these?
T. Not often, in the fruiting phase! It can depend though, with certain species liking more CO2, not too many but we are always happy to help, you can email us at firstname.lastname@example.org anytime!
Is it possible for CO2 levels to be too low? In other words, do any mushrooms require a minimum CO2 level?
Michael – I suggest starting with Oysters! A fruiting block is a great way to get acquainted with mushroom growing, and then you can venture into mixing spawn and substrate for your own fruiting blocks.
Hi Dave! Start at the lowest speed and see how that affects the humidity level in your tent. You will also want to look for signs of your mushrooms needing more fresh air, i.e., stringy or deformed fruits likely need the fan to be turned up. Every environment is unique meaning it is a trial and error process to dial in your tent and fan speed!
Recently, my wife and I decided we want to eat healthier and start growing our own veggies, but we have no idea how to get started. We loved the idea of growing our own mushrooms by building a Martha Tent, and your article made it easy to understand, so we’ll start by reading your tips carefully. Thanks for the advice on how you’d need to control your mushrooms’ surroundings and their humidity levels.
I Have a Mella growing unit coming in June : ) !!! What would You suggest I purchase to grow in it ?! T
With the bags of Mushroom Mycellium which You sell, do I just put some into a good substrate, or just our some of the bag into an appropriate sized container to grow in the Mella ?!
What fan speed do you have as a starting point with the fan unit you use. Any tips for dialing in the correct settings for the environment?
Hi Mike, we recommend looking to Amazon for the time being but we will have them in stock soon!
I couldn’t have my duct fan on 24/7 anymore so I purchased a timer so it cycles for 15 min. at a time 6x per day. Having the duct fan on all the time lowered my temperature by multiple degrees and sucked out all of my humidity. I was constantly refiling my humidifier and my mushrooms have stopped growing after pinning. I’m hoping that with the less FAE the mushrooms respond better.
I saw that your FAE (Fresh Air Exchange) Fan is sold out in your store. Are there any alternatives? A similar fan, or a low tech solution until your fan is back in stock? Thanks!
What do I do when the metal rack starts to rust from being in high humidity?
Hi Zack! The fan stays on 24/7, however, the model we are using has a speed control to dial in the ideal conditions for your environment. You could add a cycle timer if desired as well.
Hi Debra, typically, this style greenhouse comes with 3-5 shelves. We do not currently sell a smaller version of the Complete BoomRoom Kit.
Does the fae fan stay on all the time or does it cycle on & off?
I was wondering if there is a smaller version of the Martha Tent?
I have a Boomroom and humidity set to 80-90% by morning there is quite a bit of water in the drip tray is this normal? Also the humidifier only lasts 24 hours between fill ups, it’s only been set up four days out of box, thx for any input!
I’ve been using the Boom Room for a few weeks and am really liking it. However I have it installed in my basement which is conditioned but still pretty cool. Do you have any good ideas for keeping the inside tent temp more in the 70s instead of low 60s? I tried a heating mat below the base pan but it didn’t really do anything.
I have a Vivo Sun 3×3×6 with an observation window. What kind of light do you recommend for a closet grow? Like a single LED Grow Floodlight? I bought this: https://www.superbrightleds.com/moreinfo/led-grow-lights/65w-full-spectrum-led-grow-light-5-band-redblueuvirwhite-for-indoor-plant-growth/4951/11279/
I think it will be too much for mushrooms.
I was wondering if I face tent window towards a patio door if that would provide enough light since all walls are solid mylar.
I want a dual purpose grow tent for Mushrooms and for veggies in late winter early spring.
Thanks, waiting on equipment and I will be buying some spawn soon.
I just purchased a martha tent and tray, but the tray is too small, can you tell me where you got your tray and what size it is? Thanks!
What is the optimum depth of substrate in the trays you are using? Also, what are the dimensions of those trays. Thanks :)
@Bruce Berkman, You’re definitely right that some folks will flip the humidifier and fan around with success. However, we’ve found that funneling the air up and through the fan instead of down, reduces the “splash” effect at the bottom of the tent, thus reducing spores released into the environment. The openings at the bottom also provide a perfect place to pull in fresh air.
Helpful, thank you. Since both CO2 and humid air are relatively heavy, why not humidify and bring in fresh air from the top, and expel tent air from the bottom?
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