Growing Cannabis in Fall/Autumn and Winter: Overcoming the Chill

Cannabis cultivation is typically associated with warm summers and abundant sunshine. But can you grow cannabis in cold weather? The answer is yes, but there are several essential tips and tricks to keep in mind. In this comprehensive guide, we’ll provide you with all the information you need for a successful cannabis cultivation during chilly winter months.

The genetics of your cannabis plants play a significant role in your cultivation success. To achieve a respectable harvest during cold seasons, it’s crucial to start with the right genetics. Look for strains with origins in cooler regions of the world. Indica-dominant strains and landrace varieties from mountainous areas in Asia are well-suited for colder temperatures, unlike sativas. Another excellent option for cold weather growers is autoflowering strains. These strains, originating from Cannabis Ruderalis, are known for their hardiness and quick life cycle, making them ideal for early spring or late autumn harvests.

Cold weather presents two main concerns when growing cannabis. First, it can shock the plant’s root systems. Healthy roots are vital for a plant’s overall health, and cold temperatures can directly affect their well-being. When soil temperatures drop below 12°C, the plant’s metabolism significantly slows down. This slowdown leads to difficulty in water, nutrient, and oxygen absorption, potentially resulting in stunted growth or wilting. In some strains, cold weather may trigger hermaphroditism, causing the development of both pollen sacs and buds, leading to self-pollination and decreased yields. The second major concern is mold, especially when moisture is present in the air. Rainfall, snow, or frosts can accumulate on a plant’s leaves or flowers, creating ideal conditions for mold issues that can be challenging to eliminate.

To determine how cold cannabis plants can get before issues arise, we must consider the ideal temperature range for these plants. Generally, cannabis thrives at temperatures between 20-25°C, depending on its life cycle stage. Vegetating plants prefer warmer temperatures, typically coinciding with the peak of summer. In contrast, flowering plants tend to prefer slightly cooler temperatures, particularly at the beginning of autumn. The ideal soil temperature for healthy root growth falls between 15-20°C. While slight deviations from these ideal temperatures won’t necessarily be fatal for your plants, maintaining these conditions, especially when growing indoors, will ensure optimal growth.

One reason you might consider growing cannabis during cold months is to secure an extra harvest before or after the traditional growing season. To achieve this, we recommend planting autoflowering strains and germinating them late in the fall or, preferably, in late summer. Depending on the specific strain’s flowering time, your plants could be ready for harvest by mid-winter (if germinated in the fall) or mid-fall (if germinated in the summer). Keep in mind that this technique is viable in regions with mild winters or warm springs. In areas with harsh winters and unpredictable spring temperatures, constructing a greenhouse is a necessity to protect your plants from the elements.

Many indoor growers intentionally lower temperatures in their grow rooms during the bloom phase. This practice replicates the natural temperature fluctuations that outdoor plants experience and can stimulate bud development. Lowering temperatures gradually may also encourage plants to produce buds with purple hues, a desirable trait for many growers.

Growing cannabis outdoors during winter is generally not recommended unless you live in an area with mild winters and low rainfall. In such regions, you may end up with weak and unhealthy plants, along with poor harvests. However, if you are determined to cultivate outdoor plants in the cold season, here are some tips to keep them healthy and maximize your results.

If you need to bring your cannabis plants indoors to protect them from the harsh winter, do so carefully. Pay close attention to daylight hours and temperatures, and try to replicate these conditions indoors as closely as possible. For flowering plants, it’s crucial to avoid exposing them to more light indoors than they received outdoors, as this can lead to revegetation, a stressful process for the plant.

If you can’t move your plants indoors in time to save them from winter, consider planning ahead for forced flowering outdoors. Cover your plants with a light-proof structure or fabric during their new “nighttime” hours. This will give them the impression that the seasons are changing, prompting them to transition into the flowering phase accordingly.

Greenhouses offer the opportunity to cultivate cannabis year-round, provided you have control over lighting, temperature, and humidity within the structure. However, it’s essential to consider some key factors before setting up a greenhouse for your cannabis cultivation.

The choice of lighting systems for your indoor cannabis grow significantly impacts your plants’ growth, especially in cold weather. Here, we’ll explore how traditional and next-generation lighting systems handle the challenges of cultivating cannabis in cold conditions.

Traditional High-Intensity Discharge (HID) systems emit substantial heat and light, providing an advantage for preserving mother plants and cuttings during the winter months. Additionally, it’s easier to maintain the vegetative growth phase with an MH bulb under an 18+ hour light cycle during cold weather.

LED lighting systems are becoming increasingly popular among cannabis cultivators. They run cooler, emitting more light, which usually aids in environmental control. However, LEDs can run too cold during winter, potentially negating the energy savings. High humidity may also become an issue, necessitating the addition of a dehumidifier during the flowering phase.

CFLs become less effective during prolonged periods of cold weather, even with the highest wattage bulbs available. This can be problematic when battling frosty winters, potentially leading to bud rot.

One fascinating aspect of growing cannabis in cold weather is the increased likelihood of certain strains displaying beautiful lilac and deep purple shades, a highly desirable trait for many cannabis cultivators.

To enable cultivation in cold conditions and enjoy iconic strains, we’ve integrated ruderalis genetics into our exclusive variety, the HM Series LED Grow Lights. With a short flowering time of 5–7 weeks and a THC content of 14%, these lights deliver an uplifting and manageable high. Moreover, you can expect respectable yields, ranging from 170–220g/plant outdoors to 500–550g/m² indoors when the plant is ready for harvest.


Stevie Lockhart

Stevie Lockhart

Author of Technical Services, Grow Pros Solution.

About Us

Grow Pros Solutions is the NOW for Horticultural Science & Engineering. Grow Pros Solutions is one of the leading manufacturers of high-performance LED grow lights designed for cannabis cultivation. Our focus is to create top performing lighting solutions and fixtures that enable previously unobtainable and unthinkable results, increasing productivity from 30-60%. Our unwavering commitment to advancing technology and finding more efficient and sustainable solutions has made us a gamechanger for thousands of commercial and home growers. 

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