What Are The Ideal Temperature And Humidity Levels for Hemp Crops?

Industrial hemp container cultivation cannot use ordinary household air conditioners:

It requires cooling, independent dehumidification (crucial! Forced dehumidification during flowering), limited humidification, and integrated fresh air system;

It requires precise, time-segmented programmed temperature and humidity control, with automatic humidity target switching during the nutrient and flowering periods;

It needs air filtration to reduce powdery mildew and spore transmission;

The unit needs to be adapted to a moderate humidity of around 50% for extended periods, and cannot tolerate continuous condensation.

1. Seedling/Seedling Stage (Sprouting to 30cm Height)

✅ Suitable Temperature: Daytime 22-24℃, Nighttime 18-20℃

✅ Relative Humidity: 60%-70%

⚠️Prohibitions:

Humidity > 75% greatly increases the risk of damping-off and mold outbreaks; temperatures consistently > 27℃ result in etiolation of seedlings; temperatures below 15℃ cause growth stagnation.

2. Vegetative Growth Stage (Vigorous growth, long branches and leaves, before flowering)

✅ Suitable Temperature: Daytime 24-28℃, Nighttime 18-22℃

✅ Relative Humidity: 55%-65%

A day-night temperature difference of 6-8℃ is beneficial for robust branches and trunks;

High humidity should not be excessive, as it easily induces powdery mildew.

3. Flowering and Bud Formation / Flowering Period (The most critical stage, key for varieties harvested for flowers and leaves)

✅ Suitable Temperature: Daytime 22-26℃, Nighttime 17-20℃

✅ Relative Humidity: 45%-55% (Humidity must be reduced!)

Key Point (significant difference from edible fungi): High humidity is prohibited during the flowering period! If humidity is consistently >60%, flower buds are highly susceptible to gray mold and mildew, leading to flower rot and significantly reducing the quality of flowers and leaves.

4. Maturity and Pre-harvest Stage

✅ Temperature: Daytime 20-24℃, Nighttime 16-19℃

✅ Humidity: 40%-50%, maintain appropriate dryness to reduce the risk of mold

Reference Range of Limits

Short-term Maximum Tolerance Temperature: 32℃; Sustained temperatures above 30℃ → Premature aging and cessation of development

Short-term Minimum Tolerance Temperature: 10℃; Growth almost stops below 8℃, frost directly damages plants

Basic Conditions for Seed Germination: Stable soil temperature above 8-10℃ for successful seedling emergence