PC Grow Box
A micro-grow built inside a desktop computer case: discreet and educational, but limited to one small plant and 7–28 g of dry flower per harvest.
Growing, buying or possessing cannabis and seeds is legal only in some places. Check the law where you live before acting on this information.
A PC grow box is the smallest practical cannabis grow: one heavily trained plant in a gutted computer case. People really do harvest from them, but realistic yields are 7–28 g of dry flower per run, and the tight space leaves little room for mistakes with heat, smell or height. Build one for discretion or to learn the fundamentals. If you have room for a 2×2 ft tent, that will out-yield a PC case for similar running costs and is far more forgiving.
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 removed, the inside is lined with reflective material, a small LED provides light, and case fans plus a small carbon filter handle airflow and odour. From the outside it looks like an ordinary tower PC.
The usable space is typically 30–50 litres: room for one heavily trained plant, usually an autoflower or a topped photoperiod plant kept under about 40 cm tall.
Check local law first. Home cultivation is illegal in many places, and where it is allowed there are plant-count and security rules.
Why growers build them
- Discretion. A PC tower in a bedroom or office draws no attention, which suits people who want privacy from visitors, roommates or landlords.
- Space. Studios, dorms and small flats may not have room for even a 2×2 ft tent (see stealth growing setups).
- Learning. A tiny, closed space forces you to understand airflow, heat, light distance and plant training. The skills transfer to bigger grows.
What a PC grow is not good for: yield, efficiency or tall plants. Cannabis photosynthesis and yield rise with the light a canopy receives [3][5] Strong evidence, and a PC case can only fit a small light over a small canopy. A 100 W LED in a 2×2 tent gives a much larger canopy for similar electricity use Weak / limited.
Parts list
- Case: mid or full ATX tower with a removable side panel; larger is easier.
- Light: 40–100 W LED panel or small quantum board that fits under the lid. LEDs produce less heat than the CFL bulbs used in older builds Weak / limited.
- Reflective lining: Mylar, panda film or matte white paint (not kitchen foil, which tears and creates hot spots) [1] Weak / limited.
- Fans: one 120 mm intake (bottom front) and one 120 mm exhaust (top rear), ideally with speed control and rubber mounts.
- Odour control: a mini inline carbon filter on the exhaust (see replacing carbon filters).
- Container and medium: 1–3 litre fabric pot with coco coir or a light peat mix.
- Control: a plug-in timer and a hygrometer/thermometer with a remote probe.
How to build one (step by step)
- Gut the case. Remove the motherboard tray, drive cages, power supply and cables, leaving a hollow box with a removable side panel.
- Line the interior with reflective film or matte white paint.
- Mount the light under the top panel on stand-offs so heat can escape around it.
- Set up airflow with negative pressure: the exhaust should move more air than the intake, so air (and smell) leaves through the filter rather than through gaps [1] Weak / limited.
- Fit the carbon filter to the exhaust. Even one flowering plant smells strongly.
- Choose a small pot and light medium. Coco or light peat in a 1–3 litre pot stays aerated; bigger pots dry too slowly in a closed case.
- Set the light cycle. 18/6 or 20/4 for autoflowers; 18/6 in veg then 12/12 to flower photoperiods [1][2].
- Train early. Top at the 3rd–5th node and tie branches flat (LST), or stretch a small SCROG net across the case. Untrained plants outgrow the box early in flower.
- Run a dry test for 48 hours before planting, checking that temperature and humidity stay stable.
- Monitor and harvest. Aim for roughly 20–28 °C and 40–60% humidity in flower [4] Weak / limited; most growers harvest when trichomes are mostly cloudy with some amber.
Common mistakes
- Wrong genetics. A tall plant in a PC case is a failed build. Choose compact indica-leaning cultivars or short autoflowers.
- Undersized exhaust. If the case feels warm from outside, airflow is too weak. Heat builds up fast in small spaces (see heat stress symptoms) Anecdote.
- Skipping the carbon filter to save space.
- Overwatering small pots. A 1 litre pot may need water every 1–2 days, a 3 litre pot every 3–4. Judge by lifting the pot, not by schedule.
- Believing online yield claims. Photos of huge PC harvests are rarely typical; anything above about 30 g dry is exceptional Anecdote.
- Ignoring noise. Two fans plus a filter can be louder than a real PC. Use rubber mounts and speed controllers.
Related techniques
- Stealth growing setups — cabinets and other discreet builds with more usable volume.
- 100 W LED in a 2×2 tent — the usual next step up.
- Training that suits PC builds: SCROG and defoliation; for plant choice see autoflowering cannabis.
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.
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