Mastering Environmental Control so Your Indoor Garden Can Thrive

Growing indoors gives you a major advantage over growing outdoors when you’re looking for consistent results. That’s because you don’t have to rely on the weather at all. When growing indoors you are in complete control of your environment, or at least you should be. It’s up to you to learn how to manipulate your grow space to have all the right conditions for optimal growth, and we’ll explain all the different elements you need to get right for this to happen down below.

Mastering Environmental Control so Your Indoor Garden Can Thrive

Control Each of These Conditions Carefully for Indoor Growing Success

In order to grow healthy plants you need to be in control of all the different environment conditions listed below.

  • Humidity – The amount of water vapor in the grow room air.
  • Temperature – How warm or cool your room is.
  • Light – The intensity, distribution and hue of your grow room light.
  • Air circulation – Healthy grow rooms need moving air.
  • CO2 levels – The total level of CO2 gas in your grow room’s air.

Get each condition right and you’ll enjoy healthy growth from your plants.

Humidity and Temperature

Healthy plants transpire regularly and put water vapor into the air surrounding them. This is a real issue for indoor growers because that raises humidity levels. If humidity levels become too high, issues like black mold, powdery mildew and more are much more likely to occur. That’s why care must be taken to control humidity levels. Maintaining just the right humidity levels is the only way to grow quality buds that you’ll be able to use, but you’ll need some guidance and equipment to maintain these two variables accurately.

Get the Guidance You Need with Vapor Pressure Deficit Charts

Vapor pressure deficit charts tell you exactly what temperature and humidity range your plant should be in depending on what growth stage it is in. Using one of these charts is the simplest way to get a good baseline to work from when trying to optimize your grow environment to your plants.

There are different charts available for different crop strains, and when you have the right chart for your grow you can use it to adjust your indoor temperature and humidity levels throughout the different growth stages from germination all the way through the flowering stages.

Use Dehumidifiers

Powerful dehumidifiers are useful for maintaining exact humidity levels in an indoor grow room. These devices require lots of energy to operate, but lower humidity levels reliably over time.

Use Heating and Cooling Systems

There are many different solutions available to meet the temperature control needs of indoor gardeners. Whatever solution you decide on it should automatically adjust temperatures up and down to stay at just the right setting to simplify growing as much as possible. A hydroponic heating and chilling system that cools or heats from the bottom of the plants up is an ideal solution, and many advanced systems can be used to adjust humidity levels as well. Invest in a minimum of half a ton of cooling for every 1000 watts of HID lights used for good reliable temperature control that you can count on throughout the year. Consider installing UV sterilization lights on your chillers to minimize the risk of mold growth in your room, but take care to prevent UV light leaks to avoid adversely affecting your plant development during the no-light times.

Minimize Micro-Environments with Proper Pruning

Overlapping and bunched up leaves can cause what’s known as micro-environments to occur on sections of your crop. Even if your grow room is kept at around 60 percent humidity at comfortable temperatures, some sections of your plants could be sitting at 100 percent humidity if leaves are bunched together and overlapping. That’s due to transpiration, which gives off water vapor from the plant’s leaves. In these sections of the plant mold will occur more frequently.

Proper pruning can prevent this problem from occurring by keeping plants from getting too bushy and from having many leaves that overlap. Expert growers can reduce plant nodes down to one per branch, and open up the plant to healthy airflow throughout its life cycle.


Once you have temperature and humidity locked down, you need to focus on your lighting solution. Invest in a powerful HID light array that will provide the necessary blue and red light for vegetation and flowering cycles. Utilize an indoor grow chart light like the one below to help you decide how powerful your HID light array should be. Most indoor growers will be happy with an array between 400W and 1000W, but if you have a grow space larger than 6×6 you will need multiple arrays to cover the area properly.

Mastering Environmental Control so Your Indoor Garden Can Thrive

Install your lights at the proper height starting off lower during the early stages and raising it upward as your plants become taller, and also carefully adjust the on/off time cycle for your lights as your plant goes through the different growth cycles from vegetative to flowering to curing. You can control all of this using grow light timers that are fully programmable.

Air Circulation

Proper air circulation will minimize micro-climates throughout your grow room, while also making mold and mildew issues less likely and strengthening your plants in the process. Take care to avoid hitting plants with too much air flow to avoid shocking and damaging them, and instead focus on achieving a light constant breeze. Oscillating fans do this job well, and wall-mounted units are often selected for convenience purposes.

Along with a good array of fans, you will want to consider filtration to minimize airborne contaminants and the scent of your grow operation. Charcoal filters and standard air filters work well for this task. Recirculating air, rather than venting grow air directly outdoors is also a useful practice for minimizing smells.

CO2 Levels

Finally, you need to consider the CO2 levels of your grow space, because healthy plants convert CO2 into oxygen and deplete CO2 levels in the area. In an enclosed space CO2 levels will drop over time if you don’t do something about it, and it’s those diminishing CO2 levels that can hurt plant growth when you get all the other environmental conditions just right.

To effectively increase CO2 levels in your room you’ll need tanks of compressed CO2 or CO2 burners. Both can be automated to maintain optimal CO2 levels for healthy growth if you get a setup that includes a CO2 PPM meter. CO2 systems can be hazardous though to both you and your plants, so invest in an emergency shut-off system to cut off the CO2 when levels get too high.

Making the Most of Extra CO2

Some growers increase their CO2 levels to higher levels than you would find outdoors to enhance plant growth to higher rates. This strategy works well only if you’re willing to raise the temperature of your grow room as well to about 85 degrees Fahrenheit. You will have to carefully adjust humidity levels in your room to grow at these higher temperatures, but the extra effort can pay off with faster growth output.

Getting all your indoor growing conditions just right is the most difficult part of indoor gardening, and also the most important. Carefully invest in coolers, heaters, lights, fans, filters and CO2 distributors and get all the conditions just right and you’ll be amazed what a difference it makes for your plants.

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