Grow Tents: 21st Century Greenhouses
Grow tents are a convenient and relatively inexpensive way to bring the greenhouse inside. Casey Jones Fraser explains why he’s a big fan.
I have wanted a greenhouse for most of my adult life. The longing started in college, where I would work with plants in the university greenhouse on campus. For a broke college student, a greenhouse was out of the question.
I don’t know any students who have the time, money or sun-soaked property required for a working greenhouse. The alternative, in my case, was carpentry and grow lights. I started building walls and door frames in the basement of my rental house—it would take a few days to build a room and I had to add ports for ventilation and power.
Once the walls, doors and portholes were complete, I would line the room with reflective material before adding lights and fans. It took plenty of work and resources to build these grow rooms, not to mention time.
These tents are box-shaped canvas enclosures supported by metal frames. Much like a camping tent, they come in a small package and quickly expand out to full size—you can set one up in an afternoon, complete with all your growing gear. Not every grower can buy a greenhouse, but most of us can afford one of these garden huts.
Grow tents, also known as portable grow rooms or indoor greenhouses, come in a variety of sizes to suit every grower. I have seen models so small that they barely hold a few seedlings and models so large they can’t fit in my house! Most of these tents are around six feet tall and some common floor plans include two feet by four feet, three feet by three feet, four feet by four feet, five feet by five feet and 10 feet by 10 feet.
All quality tents come with lightproof zippers and multiple ports for power cables and ventilation and many more sizes are available from a variety of manufacturers. Once the tent is in place, the grower needs to supply lights, fans and the garden—either soil or hydroponics.
Lighting up the hut
For young vegetative plants and mothers (donor plants), T5 lights work quite well—these lights run cooler than metal halide so they are easy to maintain in a small space and they are lightweight so you can hang them from the support bars of your tent. For larger vegetative operations, I suggest metal halide lights on a mover. Some light-mover manufacturers are even making accessories you can use to hang the rails from your tent supports. It just keeps getting easier!
For flowering plants, more intensity might be desired. You can flower plants with T5 lights if big yields aren’t the main goal for your portable grow room—the plants will be healthy, but not nearly as rugged and heavy as plants flowered under HPS lights. Most of us are growing flowering annuals—such as tomatoes and sunflowers—so here are my lighting recommendations for flowering in some popular tent sizes:
- For a three foot by three foot enclosure with a two foot by two foot garden in the center: one 400 watt HPS or MH.
- For a four foot by four foot enclosure with a three foot by three foot garden in the center: one 600 watt HPS or MH.
- For a five foot by five foot enclosure with a four foot by four foot garden in the center: one 1000 watt HPS or MH.
- For a 10 foot by 10 foot enclosure with an eight foot by eight foot garden in the center: four 1000 watt HPS or MH.
- For a 10 foot by 10 foot enclosure with a nine foot by six foot garden in the center: six 600w HPS or MH.
These lighting suggestions are for indoor greenhouses where high yield and quality are desired. Lighting should be dialed back slightly for orchids. For tents with houseplants and decorative gardens, go with T5 lighting. LED lights are getting more common for grow tents, but this author is still on the fence about current LED technologies.
Best fans and blowers for grow tents
Every grow tent needs fans—even if you have some new fangled ‘cool-running’ grow light. Your plants need air circulation and most of us require cooling fans to keep our rooms in the mid to upper 70s. A gentle breeze, evidenced by leaf movement, will increase growth and deter mold.
A local grower once told me he won’t use fans on his tomato plants because the movement of air makes his house smell like tomatoes and organic fertilizer. If you aren’t concerned with plant health, yield or quality, then I guess fans are optional—the rest of us will use fans and remove the organic odors with carbon filters.
Circulation fans might get caught up against the canvas of your grow tent. Here we see a six inch net cup attached to a fan with zip ties. The net cup allows airflow and the back of the fan stays unobstructed—this ensures maximum air movement and minimum resistance. Fans are placed in the corners, each fan facing a different direction. This creates a vortex of air movement when the tent is closed.
Power supply and grow tents
Before I set up my grow tents, I had a qualified electrician install dedicated circuits for my gardens. We ran solid-core cables from the breaker box and installed the outlets on the ceiling directly above each tent. I can easily plug in all of my equipment and I have yet to trip a breaker.
Once you have been trained in electrical installation, it becomes easy to add power outlets anywhere you need them, but you should never install power supplies if you are inexperienced. Instead, hire a professional. Poorly planned electrical installations can lead to fire and even death.
Oscillating fans are ideal in a large room, but not for most grow tents. One option is to install inexpensive stationary fans in each corner to create total air circulation throughout the garden space.
Outside of the grow tent, consider using two six inch blowers. The top blower is used to pull air through the carbon filter, through the HID reflector and out of the tent and the bottom blower pushes air back into the tent. With this set-up, CO2 equipment is placed outside of the garden, where it can be used to supplement multiple tents in one space.
Hanging the heavies
I like big heavy carbon filters and extra-large reflectors. What can I say—grow big or go home! But seriously, it gets a bit tricky mounting this heavy steel equipment over my prized plants.
In a commercial greenhouse, the structure is built with heavy-duty braces, which can easily handle heavy equipment. For indoor greenhouses, the framework is only capable of handling moderate weight. Check with your local grow shop, because you might want to fortify the frame with accessories made by grow tent manufacturers.
I have seen a new skeletal support system that slips over existing framework. With the extra support, you can hang all of your equipment and still do chin-ups from the crossbars.
If the support system is not an option for you, you could install hooks into the ceiling above your grow tent. With chain or steel cables, hang a two by four board about a half inch from the grow tent. Now you can poke small holes in the roof of your tent and screw hooks into the two by four. This hanging stud is supported by ceiling hooks and will hold heavyweight grow gear. Test the stud with a few quick chin-ups—if it supports your body weight it will hold your carbon filter.
This DIY options have the unfortunate disadvantage of permanent holes in the tent, which can cause light leaks, CO2 loss, or even bug infestation. If you want professional support with no holes and no damage to the ceiling, get the slip-on frame support.
If you need to mount gear to the walls, just pick up a hanging wall rack. These wall racks take about 30 seconds to put in your tent, and now you can mount oscillating fans, thermometers, CO2 controllers, etc., on the sides of your garden.
Should I use soil or hydroponics in a grow tent?
I have seen growers experience success with various growing methods, so you must decide for yourself whether to grow in hydro or soil. I am a big fan of soilless mixes—which look like soil, but technically are not.
For soil and soilless mixes, you can grow in pots, grow bags, fabric containers or large beds. You might need to install a drainage line in the side of your tent near the base. This soilless bed garden is equipped with drainage, which is plumbed out of the tent.
Heavy-duty casters are used to shift the garden a few inches in any direction. If you choose to go hydro, consider raising your tent off the floor—you can support the tent with tables or build a frame.
With the tent raised the hydroponic reservoir can sit directly on the floor under the tent, which will keep your nutrient solution cool as it will not be heated by your grow lamp. In general, reservoirs will stay cooler when kept on a concrete floor.
Nutrient solutions should always be at 72°F, or slightly cooler. Your hydro tray will sit on the floor of the tent, giving you maximum vertical space for plant growth.
The beauty of all-in-one grow tent packages
Nope—not that big embarrassing fold in your khakis when you sit down. I’m talking about kits that come with a grow tent, lights and various grow gear. If you are new to growing indoors, these kits are a great way to get your indoor greenhouse up and running.
If your local grow store doesn’t have pre-packaged kits, find out what discounts are available if you buy everything in one shot. Most of the sales people I know in this industry have used these garden huts, so you can expect some practical advice.
Check out the display tents in the shop and measure your space at home—with a small budget and a checklist, you can go from zero to pro grow in one day. Good luck and get growing!