Indoor growing conditions

VPD and indoor growing conditions

Growing cannabis indoors can be a rewarding endeavor, but it’s important to ensure that the plants are grown under optimal conditions. In this blog post, we’ll discuss the ideal environmental conditions for indoor cannabis growing and the importance of Vapor Pressure Deficit (VPD) in achieving the best possible results.

Temperature and Humidity

Temperature and humidity are two critical factors to consider when growing cannabis indoors. Ideally, the temperature should be kept between 70-85°F (21-29°C) during the day and around 10°F (5°C) cooler at night. Higher temperatures can cause stress and reduce yields, while lower temperatures can slow growth and increase the risk of disease.

Humidity is also an essential factor in cannabis growth. In the vegetative stage, humidity should be kept between 40-70%, while in the flowering stage, it should be kept between 40-50%. High humidity levels can cause mold and mildew to develop, while low humidity levels can cause the plant to dry out.


Cannabis plants require high-quality light for proper growth and yield. LED grow lights are the most popular choice for indoor cannabis growers due to their efficiency and versatility. They can also be adjusted to different spectrums, which can be beneficial during the different growth stages.

When using LED grow lights, it’s essential to maintain an appropriate distance between the light and the canopy of the plants. This distance will vary depending on the intensity of the light and the growth stage of the plant. A good rule of thumb is to keep the light between 12-24 inches (30-60 cm) away from the canopy.


Nutrients are essential for cannabis growth, and the right balance of nutrients is crucial to achieve the best possible results. There are several types of nutrients that cannabis plants need, including nitrogen, phosphorus, and potassium. In addition to these macronutrients, there are also micronutrients that the plant requires, such as iron, zinc, and copper.

It’s essential to use high-quality nutrients that are formulated specifically for cannabis plants. Overfeeding or underfeeding can cause stress and reduce yields, so it’s crucial to follow the manufacturer’s instructions carefully.

Vapor Pressure Deficit (VPD)

Vapor Pressure Deficit (VPD) is a measure of the difference between the amount of moisture in the air and the amount of moisture the air can hold when it’s saturated. It’s an essential factor to consider when growing cannabis because it affects the plant’s ability to absorb water and nutrients.

VPD is measured in kilopascals (kPa) and is determined by calculating the difference between the vapor pressure (VP) and the saturation vapor pressure (SVP) at a given temperature.

To achieve optimal growth and yields, cannabis plants require a specific VPD range during each growth stage. In the vegetative stage, VPD should be kept between 0.8-1.3 kPa, while in the flowering stage, it should be kept between 1.0-1.5 kPa.

Maintaining the proper VPD range can be challenging, but it’s critical for the health and productivity of the plants. It’s recommended to use a hygrometer to measure the temperature and humidity, and a VPD chart to calculate the VPD for a specific temperature and humidity range.

Final Thoughts

Growing cannabis indoors requires careful attention to environmental conditions, lighting, nutrients, and Vapor Pressure Deficit (VPD). By providing the right conditions for the plants, you can achieve optimal growth and yields. It’s also important to monitor the plants regularly for signs of stress or disease and adjust the growing conditions as needed. Even simple tools like the rope ratchets to adjust light height can be really useful as this helps you get the perfect light height from your plants canopy.

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About Me

Hi, I’m Hugo, owner of TheGroBro. I built this company from my passion for growing plants, especially Cannabis. Your plants are very important to us and we will guide you through the process as much as possible.

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