CO₂ for Cannabis: When to Cease CO₂ During Flowering

The Complete Guide to Using and Halting CO₂ for Cannabis Growth

The advantages of CO₂ enrichment in indoor cultivation setups are well-known within the growing community. However, determining the optimal application and cessation of CO₂ usage remains a topic of debate among growers.

In this comprehensive article, we’ll delve into how plants utilize CO₂, the ideal CO₂ levels for cultivation, and the precise timing for introducing this supplement. We’ll particularly focus on when to initiate CO₂ in the grow room and when to halt CO₂ during the flowering stage. Let’s delve deeper into this crucial aspect of cannabis cultivation.

Maximizing Cannabis Growth: Understanding CO₂ Usage

The utilization of carbon dioxide (CO₂) in cannabis cultivation is pivotal for achieving robust growth and bountiful yields. But how exactly do plants harness CO₂, and when is the optimal time to introduce or cease its supplementation?

In this comprehensive guide, we’ll explore the mechanisms by which plants utilize CO₂, delve into the ideal CO₂ levels for different growth phases, and provide expert insights on the strategic application and cessation of CO₂ supplementation, particularly during the flowering stage. Let’s delve into the intricate world of CO₂ in cannabis cultivation.

How Plants Utilize CO₂

Plants undergo photosynthesis, a vital process where they convert carbon dioxide (CO₂) into sugars, which serve as energy sources and building blocks for organic molecules. This process, known as C3 photosynthesis, occurs within specialized cellular structures, resulting in the production of energy-rich compounds crucial for plant growth.

To facilitate efficient CO₂ utilization, plants rely on a molecule called RuBisCO, which assists in transporting CO₂ molecules to sites of photosynthesis. However, under stressful conditions such as high temperatures or intense light exposure, RuBisCO may struggle to meet the plant’s CO₂ demands, hampering growth and development.

Ideal CO₂ Levels for Indoor Cultivation

Determining the optimal CO₂ concentration involves various factors, including plant species, growth stage, and environmental conditions. While there’s no universally prescribed parts per million (ppm) concentration, some general guidelines exist.

  • Seedling Stage: Seedlings absorb CO₂ from the atmosphere and typically do not require elevated levels for growth.

  • Vegetative Stage: During this phase, maintaining CO₂ levels between 800 and 1200 ppm promotes vigorous growth and foliage development.

  • Flowering Stage: Elevated CO₂ concentrations ranging from 1200 to 1500 ppm can enhance photosynthesis, leading to larger, denser buds and improved yields.

Best Practices for CO₂ Usage

Achieving optimal CO₂ levels involves meticulous monitoring and strategic supplementation throughout the plant’s life cycle. Here are some recommended practices:

  • Regular Monitoring: Utilize a CO₂ meter to track levels within the optimal range of 700-1600 ppm, adjusting supplementation as needed.

  • Promote Air Circulation: Ensure adequate airflow to prevent CO₂ buildup and maintain optimal temperature and humidity levels, mitigating the risk of mold and disease.

  • Select Suitable Supplements: Choose from various CO₂ sources, such as tanks, generators, or bags, based on your cultivation scale and requirements.

Timing CO₂ Supplementation

Determining when to initiate and cease CO₂ supplementation is critical for maximizing its benefits:

  • Seedling Stage: Generally, CO₂ supplementation is unnecessary during this phase, as seedlings absorb CO₂ from the ambient air.

  • Vegetative Stage: Begin CO₂ supplementation once plants enter the vegetative phase, maintaining levels between 800-1200 ppm to support robust growth.

  • Flowering Stage: Increase CO₂ concentrations to 1200-1500 ppm during flowering to bolster bud development and maximize yields.

  • Late Flowering Stage: Cease CO₂ supplementation during the final weeks of flowering to prevent unnecessary stress and optimize bud maturation.

Monitoring and Adjustment

While adhering to recommended CO₂ levels, closely monitor plant health for signs of stress or imbalance. Adjust CO₂ supplementation gradually to avoid shocking plants and maintain optimal growth conditions.


Understanding the nuances of CO₂ supplementation is essential for maximizing cannabis growth and yield potential. By implementing strategic supplementation practices tailored to each growth phase, growers can harness the power of CO₂ to cultivate healthy, thriving plants and achieve superior harvests.

FAQs about Ceasing CO₂ During Flowering

What are the ideal CO₂ levels during the flowering stage? 

During flowering, maintain CO₂ levels between 1200 and 1500 ppm to promote robust bud development and enhance yields.

Is CO₂ supplementation necessary during flowering? 

Yes, CO₂ supplementation during flowering can significantly improve bud quality and yield, provided levels are maintained between 1200-1500 ppm.

Can CO₂ supplementation lead to bigger buds? 

Proper CO₂ supplementation during flowering can indeed contribute to larger and denser buds, resulting in higher-quality yields. Aim to maintain CO₂ levels within the recommended range of 1200-1500 ppm for optimal results.

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