PC Grow Box
A stealth micro-grow built inside a desktop computer case, capable of producing a few grams to an ounce per harvest.
A PC grow box is the smallest practical cannabis grow you can build. It's a real thing people do — and people really do harvest from them — but expectations matter. You're not pulling QPs out of a Dell tower. Realistic yields are 7–28 grams of dry flower per run from a single plant trained heavily. The appeal is stealth and learning, not productivity. If you have a closet or a 2x2 tent available, use that instead.
What a PC grow box is
A PC grow box is a cannabis micro-grow built inside a repurposed desktop computer case — usually a mid- or full-tower ATX chassis. The motherboard, drives, and power supply are stripped out, the interior is lined with reflective material, a small LED replaces the lighting, and the original case fans (or upgraded ones) handle intake, exhaust, and carbon filtration. From the outside it can look like a normal, if slightly humming, tower PC.
Internal grow space is typically 30–50 liters. That's enough for one heavily trained plant or, with a SCROG net, a small canopy. Most builders run a single autoflower or a topped photoperiod plant kept under 40 cm tall.
Why growers use them
There are three honest reasons to build one:
- Stealth. A PC tower in a bedroom or office draws zero attention. This is the dominant use case in regions where home cultivation is illegal or where roommates, landlords, or family are a concern.
- Space. Studios, dorms, and small apartments may not have room for a 2x2 tent.
- Learning. A PC build forces you to understand airflow, heat, light distance, and plant training in a constrained system. Skills transfer.
What a PC grow is not good for: yield-per-effort, energy efficiency, or growing large sativa-leaning phenotypes. A 2x2 tent with a 100W quantum board will out-yield a PC box several times over for similar electricity cost Strong evidence.
When to start
Build the box before you germinate. Cannabis seedlings move fast — within 2–3 weeks of sprouting an untrained plant in a PC case will already be hitting the lid. Have lights, fans, filter, pot, and medium installed and tested for at least 48 hours of dry runs (temperature and humidity stable) before a seed goes in.
For strain choice, pick an autoflower indica-dominant variety bred for short stature, or a known short photoperiod cultivar. Avoid anything described as 'stretchy,' 'sativa-dominant,' or 'tall.'
How to build one (step-by-step)
1. Gut the case. Remove motherboard tray, drive cages, PSU, and all cables. You want a hollow box. Keep the side panel removable for access.
2. Line the interior. Use Mylar, Panda Film, or matte white paint. Avoid household aluminum foil — it creates hotspots and tears easily Strong evidence.
3. Install lighting. A 40–100W LED panel or quantum board sized for the lid works best. Old CFL builds still circulate online, but modern small LEDs are cheaper to run and produce less heat Strong evidence. Mount the light to the underside of the top panel with standoffs for airflow.
4. Set up airflow. You need negative pressure: exhaust CFM must exceed intake CFM. A typical build uses one 120mm intake fan (bottom front) and one 120mm exhaust fan (top rear) pulling through a small carbon filter. Negative pressure pulls smell through the filter rather than leaking it out seams [1].
5. Add a carbon filter. This is non-negotiable for stealth. Even a small flowering plant produces noticeable terpene output. Pre-built mini inline carbon filters fit most cases; otherwise DIY with activated carbon and a mesh tube.
6. Choose a pot and medium. 1–3 liter fabric pots fit most PC cases. Coco coir or a light peat mix works well in small containers because they're easier to keep oxygenated than dense soil Strong evidence. Larger pots dry too slowly in a confined space.
7. Light cycle. 18/6 or 20/4 for autoflowers; 18/6 veg then 12/12 flower for photoperiods. Use a mechanical or digital timer.
8. Train aggressively. Top the plant at the 3rd–5th node, then LST every main branch horizontally. A SCROG net stapled across the case interior keeps the canopy flat under the light Strong evidence. Without training, the plant will outgrow the box in week 2 of flower.
9. Monitor. Keep temps 20–28°C and humidity 40–60% in flower. A cheap hygrometer with a probe through a cable grommet is enough.
10. Harvest at 8–12 weeks. Trichomes mostly cloudy with some amber is the standard cue Strong evidence.
Common mistakes
- Picking the wrong genetics. A tall plant in a PC case is a dead build. Stick to compact indicas or short autos.
- Underpowered exhaust. If the case is warm to the touch from outside, your airflow is undersized. Heat is the #1 killer in micro-grows Strong evidence.
- Skipping the carbon filter to save space. You will smell it. Your neighbors might too in late flower.
- Overwatering small pots. In a 1L pot you may water every 1–2 days; in a 3L pot every 3–4. Lift the pot to judge weight rather than going by a schedule.
- Believing yield claims online. Photos of 'half-pound PC grows' are essentially never real. Anything above ~30g dry from a single PC case is exceptional, not typical Anecdote.
- Ignoring noise. Two 120mm fans plus an inline can be louder than a real PC. Use rubber-mounted fans and variable speed controllers.
Related techniques
PC grows sit in a family of micro-cultivation methods. If you have slightly more space or flexibility:
- Space bucket — a stack of 5-gallon buckets; similar volume, easier to build, slightly higher yields.
- Cabinet grow — converted dresser or filing cabinet; substantially more usable volume.
- Micro grow tent — purpose-built 2x2 or smaller tents.
Training techniques that pair well with PC builds: topping, LST, SCROG, and defoliation. Plant selection: autoflowering cannabis and compact indica cultivars.
Sources
- Book Cervantes, J. (2006). Marijuana Horticulture: The Indoor/Outdoor Medical Grower's Bible (5th ed.). Van Patten Publishing.
- Book Rosenthal, E. (2010). Marijuana Grower's Handbook: Your Complete Guide for Medical and Personal Marijuana Cultivation. Quick American Publishing.
- Peer-reviewed Chandra, S., Lata, H., Khan, I. A., & ElSohly, M. A. (2008). Photosynthetic response of Cannabis sativa L. to variations in photosynthetic photon flux densities, temperature and CO2 conditions. Physiology and Molecular Biology of Plants, 14(4), 299–306.
- Peer-reviewed Potter, D. J. (2014). A review of the cultivation and processing of cannabis (Cannabis sativa L.) for production of prescription medicines in the UK. Drug Testing and Analysis, 6(1-2), 31–38.
- Peer-reviewed Eaves, J., Eaves, S., Morphy, C., & Murray, C. (2020). The relationship between light intensity, cannabis yields, and profitability. Agronomy Journal, 112(2), 1466–1470.
- Reported Leafly Staff (2019). 'How to build a stealth grow: beginner's guide to micro-growing.' Leafly. ↗
- Government Health Canada (2022). Personal production of cannabis for medical purposes: information for applicants. ↗
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