Growers Blog: Environment

By cch2o

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Environment is everything when growing high value crops. It is the basis for success that a great harvest is built upon. This begins with dialing in environmental conditions such as temperature, humidity, pH, ppm/EC, CO2 and water temperature. Great care must be taken to ensure plants receive these environmental requirements to produce at their optimal levels. Below you will find information guiding you on the correct environmental conditions when growing in the Under Current.


Proper grow room temperature is crucial for plants ability to carry out important functions such as photosynthesis and transpiration. Within natural environments plants can regulate these functions efficiently. However, plants grown in Controlled Environment Agriculture (CEA) are entirely dependent on the grower to supply these environmental conditions required for optimal growth.

Temperature directly affects a plants ability to photosynthesize (the process by which plants turn carbon dioxide, water and light into energy) and transpiration (the process of moisture being carried throughout the plant and released through leaves into the atmosphere). These crucial processes can only be achieved efficiently when temperature, and other factors such as humidity, are within the plants optimal range. Anything outside of this optimal range and gardens become less efficient, leading to poor quality harvest or even complete crop loss.

Low Temperatures

Grow room environments with low temperatures will cause plants to slow down their evaporation process. This results in slowed growth and increased risk of dangerous pathogens such as fungus and mildew.

High Temperatures

At high temperatures, plants will be will begin to conserve water by slowing down or ceasing the transpiration process. Much like the human body sweating to keep cool, plants transpire to regulate their temperature. When continuously exposed to high temperatures plants will lose this ability, resulting in slowed growth and/or poor quality harvests. As a response to high temperatures in the vegetative stage plants will stretch excessively, while plants in their flowering stage will have flowers that are light, airy and dry.


Working in conjunction with temperature to create the ideal environmental conditions, humidity is crucial for plants to thrive and produce to their full potential. Humidity is directly affected by atmospheric temperature; warmer temperatures can hold an increased amount of moisture when compared to colder temperatures (ex: A room at 70% RH / 85° will hold more atmospheric moisture vs a room at 70% RH / 45°). It is this relationship that requires equal attention to both humidity and temperature when dialing in environmental conditions.

Moisture within the atmosphere at any given moment is measured and represented by relative humidity (RH), which is determined by environmental temperatures. Plants contribute to humidity naturally by utilizing only 5-10% of the water they absorb. The remaining 90-95% is released into the atmosphere during the transpiration process.

During this transpiration process, plant and environment attempt to find equilibrium. In low RH environments water is essentially drawn from plants to replace the lack of moisture within the atmosphere. The moisture drawn from the plant during this process is often taken at a rate that cannot be replaced efficiently, resulting in plant tissue damage.

Low Humidity

Low RH results in crispy, wilting leaves and poor quality product. Plants may also uptake nutrient solution at an increased rate, in an effort to replace lost moisture, potentially causing nutrient burn.

High Humidity

High RH environments in combination with inadequate airflow increase the risk of dangerous pathogens such as fungus and mildew taking a hold on a garden. This environment also provides the ideal living conditions for many garden pests.


The ideal range for pH in the Under Current system is 5.5-6.5, it is at this range that plants can efficiently absorb the essential elements required for successful growth and production. Correct pH levels used in conjunction with a quality nutrient line, such as Cultured Solutions premium hydroponic nutrients, will prevent any nutrient deficiencies that can affect a quality harvest.

  • Tip: It is recommended to not add concentrated pH adjusters directly to the system, this can result in plant root shock. Utilizing a top-off reservoir is a safe way of mixing all nutrient and pH concentrates without causing stress to plants.


The Under Current is a high-performance system designed to deliver high levels of dissolved oxygen and circulation to plants root structure. These conditions allow plants to uptake water and nutrients more efficiently, thus fewer nutrient (ppm/EC) inputs are required to obtain the increased yields and quality known to the Under Current system.

Typical forms of gardening (soil, coco, rockwool etc) often require ppm levels in excess of 700 ppm / 1.0 EC for young plants, and regularly exceeding 1000 ppm/ 1.4 EC for flowering plants. Because of the Under Currents increased efficiency nutrient levels this high are not required, in fact they can slow down plant growth rates, hurting yield and quality.

High ppm / EC

Plants will begin to slow down the uptake of water and nutrients, hindering growth rates and plant performance. Prolonged exposure to high nutrient levels will result in nutrient lock-out, where plants slow down/cease all uptake of water and nutrients as a natural defense mechanism to conditions of high stress. Signs of nutrient lock out include: stunted growth, yellow foliage, leaf curing and tip burn.

  • Tip: Any adjustments to nutrients should be done incrementally, paying special attention to how plants respond to these changes. Utilizing a quality nutrient line such as Cultured Solutions will insure your plants receive all macro and micro nutrients required for explosive growth.

Water Temperature

To get the most out of your garden it is recommended to utilize a water chiller in conjunction with the Under Current system. Water chillers will keep water temperatures within the optimal range (65-68°), allowing high levels of dissolved oxygen to be accessible to the root structure, while also strengthening plant disease suppression.

As water/nutrient temperature warms, its ability to hold dissolved oxygen diminishes. This high temperature, low oxygen environment provides a suitable habit for anaerobic pathogens, such as root rot, to take hold. This low oxygen environment also reduces the amount of nutrient uptake possible, limiting the potential for explosive root growth known to the Under Current system.

  • Tip: Cooler water temps will also act a heat sink in the grow room environment allowing for warmer temperatures required for optimal CO2 absorption.


Supplementing CO2 within the grow room can be used to increase growth rates and yields. It is recommended to utilize slightly warmer temperatures within the grow environment to fully take advantage of CO2 enrichment. These higher temperatures are needed to increase the metabolic rate of plants allowing them to utilize the increased CO2 available.

  • Tip: Increase grow room environmental temperatures by 5-10% and nutrient strength by 5-10% when using CO2 enrichment.

So what are the ideal environmental conditions for plants grown in the Under Current System? This depends on the growth stage plants are in, throughout their growth cycle plants will have varying environmental requirements. Refer to the Current Culture H2O General Recommendations for a comprehensive guide for temperature, humidity, pH, ppm/EC, CO2 and water temperature when growing in the Under Current.

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