Building Your Grow Room On a Budget: Part 2

Everyone ready for Part II? Time to dive in and get growing!


Colder temperatures (< 70° F or 20° C) and hotter temperatures (> 85-90° F or 32° C) inhibit growth by slowing photosynthesis and stressing out your plant.

Ideal temperatures for growing medicinal marijuana indoors are between 70-75° F (21-24° C) during “day” cycles and 60-65° F (16-19° C) during the “night.”

Growing Marijuana Indoors
T5-cfl lights & some Lasko 16in oscillating stand fans from home-depot. Photo courtesy of Miss MMJGeek

If you run into problems with over-heating, which happens most often due to the heat output from lamps, you can regulate temperature with an A/C unit, although this is a pretty expensive solution. For a cheaper alternative you can simply increase your number of oscillating fans. You can get these for a reasonable price at stores like Home-Depot: Lasko 16in oscillating standing fan–$24.96.A cool trick to consider if you live in a region with warmer climates is to run your “day” cycles at night when the temperatures drop. The best thing about an indoor grow is that you can make the sun come out whenever you’d like and this method ensures that heat output from your lamps aren’t contributing to already warm temperatures, making cooling down your grow room less of an uphill battle.

You want to maintain your humidity levels between 60-70% during vegetative stages and 40-60% while flowering. If you run into problems with high humidity any simple household dehumidifier will do the trick; this solution can range as cheap or as expensive as you’d like depending on your budget. Even a cute little Hello Kitty one would get the job done. Quickly browsing on Target’s website a dehumidifier valued at $43.99 works great for an 800-1000 sq. ft. room, so needless to say this would suffice for a small closet grow.

MH Bulb and Carbon Filter

MH bulb with carbon filter attached– carbon filter’s role truly kicks in during flower when the girls get stinky! Although I didn’t dedicate a segment to carbon filters in this entry it is important to know that you will definitely need one, especially if you wish to remain low-key. While carbon filters may run pricey, you may find ONA gel to be a quick and inexpensive fix— especially if you have a smaller closet grow op. But remember spending the extra bucks is totally worth it!


Fresh air supply and constant air circulation are essential, yet often overlooked components of an indoor grow room. There needs to be at least one fresh-air intake in every room. This can be as simple and cheap as an open door or window, or you can get a little more complicated and actively induce flow via air ducts to and from the outdoors (but what you gain in better ventilation you lose in stealth if not executed properly). A standard oscillating fan works well to circulate air and maintain great air flow—remember you want to keep your ladies dancing.

CO2 is one of the two raw materials (water being the other) required for plants to photosynthesize. Cannabis uses CO2 when, and only when, in the presence of light. The amount of CO2 in the air directly affects the rate of photosynthesis and plant growth. The most effective way to supplement your grow space with CO2 is by using a meter, regulator and tank kit. This will be slightly more expensive, but a worthy investment if you have a large space to control.

Before stating “ideal” levels of CO2, let’s quickly introduce an enzyme called Ribulose-1, 5-bisphosphate carboxylase oxygenase—usually shortened to RuBisCO. The only thing you need to know about this molecule is that once it interacts with CO2 a series of chain reactions begin and a product is made from which sugars (energy) can then be derived. RuBisCO is heavily moderated so it is only active when it should be. This is where its partner, RuBisCO activase, comes into play. RuBisCO activase is a light activated protein and its main role is to kick-start RuBisCO’s activation. Just think of RuBisCO activase as the guy that turns inactive RuBisCO into active RuBisCO.

So why bring up RuBisCO and RuBisCO activase? Because RuBisCO activase is inhibited at CO2 levels > ~1,200 ppm and its inhibition affects photosynthesis. Thus, the ideal ranges for CO2 during “day” cycles are between 1,000-1,200ppm and between 500-750ppm during “night” cycles.

HPS Bulb
HPS bulb, Jillybean clones in mid flower. Photo courtesy of Miss MMJGeek

Alternative and inexpensive delivery methods of CO2 include water heaters, gas appliances, dry ice (my personal favorite), chemical reactions, and even cheaper—biological processes such as animal respiration. So if you have puppies let them run free in your garden! If not, spending plenty of time with your ladies could also contribute, just don’t hyperventilate and make yourself light-headed in an attempt to keep your girls happier. Fermentation and composting are also great ways to supply CO2 to your grow space.


Eventually, the larger your garden becomes the thirstier your ladies will get.  You’ll then find yourself with an at-home exercise regimen hauling buckets of water as your floor space begins to expand. For example, a 10 X 10-foot (3 X 3 m) garden could use more than 50 gallons (190L) per week, making carrying water a labor intensive project. One gallon (3.8 L) of water weighs eight pounds (3.6kg); imagine having to carry 50 gallons X 8 = 400 pounds (180 kg) of water per week! As you can imagine, larger operations and collectives have more intricate irrigation systems that eliminate back-breaking labor for growers. However for a first time grower cultivating in a smaller work space an orange homer 5-gal bucket from Home-Depot (which will cost you a whopping $2.60 a pop) is all that you will need to supply your thirsty ladies during water-feedings. Remember ideal pH levels in soil are between 5.9-6.5, with ideal levels of nutrient absorption falling between 6.2 or 6.3.

pH balanced plant water
Feeding the girls with 5gal buckets. Photo courtesy of Miss MMJGeek


Nutrients are vital to maintaining healthy cannabis plants, as well as boosting the overall quality and quantity of your harvest. When looking into nutrients the cheapest option is generic fertilizers, but this is a sensitive topic as every grower is strongly opinionated with regards to nutrients. Don’t even get me started on the age old battle between synthetics vs. organics. Personally, I would not invest in cheap alternatives when it comes to the food you are feeding your babies, but this is just my personal opinion. If you are on a budget and have to use generic fertilizers a good rule of thumb is to scope out nutrients designed for edible plants since they’ll be safest to use in your medicinal marijuana garden. When sourcing fertilizers keep in mind that the two absolutely necessary nutrients for vigorous and successful cannabis cultivation are:

  • A grow nutrient heavy in Nitrogen
  • A flower/bloom nutrient heavy in Potassium and Phosphorous
Marijuana Growing Nutrients
Feeding time! Choose your nutrients wisely. Give your girls the love they deserve. Photo Courtesy of Miss MMJGeek

If the girls need anything else (usually cal-mag or B vitamins) they will be sure to scream it out at you immediately—you just have to take the time to listen.

It is possible to pick up quality soil or soilless mediums that don’t immediately require added fertilizers at your local nursery or hydro store, but eventually you will find yourself looking into supplements. Buying molasses and mixing it into your feed water is a cheap and effective carb-booster which provides a great energy source for your growing/flowering medicinal plants.

I hope this article has helped break down the basics of what a medical cannabis plant needs to grow vigorously indoors and under controlled conditions while, describing not only the best solution to provide these needs but also inexpensive yet efficient alternatives for growing on a budget as well. As a first time grower you will see that as your passion prospers so will your floor plans for future grows. Any grower can show you their humble beginnings in a closet or even a box as you walk through their present-day larger gardens. My philosophy is that the experience and knowledge from one grow fuels the expansion of the next, you just have to take it one step at a time. And remember there are better and more expensive routes that you can take, but at the end of the day you’ll realize that KISS (keep it simple stupid) works great!

If you’re interested in reading future, here are some great resources I’ve found in my own grow room journey.

Jorge Cervantes’ Marijuana Horticulture: The Indoor/outdoor Medical Grower’s Bible.

“Compact Fluorescent (CFL) Grow Lights.” How to Grow Marijuana.

Ed Rosenthal’s  Marijuana Grower’s Handbook: Ask Ed Edition