Can You Grow Weed in the Winter? Everything You Need to Know

Cannabis might be famous for thriving in warm climates, but the arrival of winter doesn’t mean you need to give up your homegrown weed garden. These plants can actually thrive during winter, as long as you treat them right. (And you can always order flower year-round if your green thumb fails you.)

Key Takeaways

• Winter can present certain challenges, but it's possible to grow weed inside a greenhouse with the right equipment.
• Heaters and insulation are crucial to maintain a constant temperature, which ensures healthy plant growth.
• Monitor both the air and soil temperature to ensure you avoid damaging your plants.
• Use a dehumidifier or humidifier and fans to ensure your plants don’t get too moist, as this can cause rot.
• You’ll likely need some grow lights to compensate for weaker winter sunlight, but remember to give your plants 12 hours of darkness once they’re large enough.
• The exact equipment you’ll need, and how you should care for your plants, will depend on the climate in which you’re growing.

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Can Weed Plants Survive the Winter?

Unfortunately, cannabis plants can't handle cold temperatures very well. Anything under 60 degrees Fahrenheit (15 degrees Celsius) can damage your plants. 

For anyone living in colder climates, that means practically half of the year is out of bounds for growing cannabis outdoors. Perhaps more, if your home's winter season stretches into spring and fall. Or does it?

You can't grow cannabis outdoors during cold weather, but an ideal grow space (such as a greenhouse) can promote healthy vegetative growth. 

Creating and maintaining that space requires time, effort, and money. But if you really want to keep growing green with snow on the ground, all that will be worth it.

(And if you decide this all sounds like too much for some cold season cannabis, you can always buy edibles online during the winter months.)

Cannabis Plants and Temperature

One of the key considerations is temperature. Hemp is a somewhat hardy plant, but still does best when kept within a narrow range of temperatures. 

Too hot, and you could end up with fewer, smaller, and weaker flowers. Too cold, and your plants could grow far slower than usual, or even die.

Unfortunately, what counts as too hot and cold can change depending on what stage of plant growth your crop is in.

Best Temperature During the Seedling Stage

The first step when growing cannabis is to plant your seeds or seedlings. These little guys are fragile. Consistent warmth is key to keeping them alive.

Generally, you should keep your seedlings at temperatures between 68 and 77 degrees Fahrenheit. (20 to 25 degrees Celsius.) Maintain that temperature during both day and night. 

Best Temperature During the Vegetative Stage

This stage usually begins about two or three weeks after your seedlings first appeared from the soil. They're still fragile, so keep a close eye on the temperature.

During the day, maintain temperatures between 72 and 82 degrees Fahrenheit. (22 and 26 degrees Celsius.) 

Why the extra heat? Well, remember that in nature the vegetative stage would normally occur during the hot summer months. We want to replicate this ideal environment inside our greenhouse.

At night, cooler temperatures are fine. Something between 64 and 72 degrees Fahrenheit is ideal. (18 to 22 degrees Celsius.)

Best Temperature During the Flowering Stage

You're almost there, but don't relax just yet! Maintaining perfect temperatures during night and day is crucial.

Keep daytime temperatures between 68 and 78 degrees Fahrenheit. (20 and 26 degrees Celsius.)

At night, let things cool to between 64 and 72 degrees Fahrenheit. (18 to 22 degrees Celsius.)

Remember that this stage in the plant's life cycle would occur during the fall in nature. Therefore, flowering plants do best in slightly cooler temperatures.

How to Measure Temperature When Growing Weed Indoors

You might think this is a simple question. After all, thermometers aren't exactly a new invention.

However, growing weed indoors is a little more complex than that.

There are actually two different temperatures you want to track. The first is the air temperature, or the temperature of the leaves, buds, and flowers. The second is the soil temperature.

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Air Temperature

The temperatures listed above are all air temperatures. In general, anything between 20 and 25 degrees Celsius should be safe. 

If the air gets too cold, your plant's leaves could generate less energy from light, slowing down growth. They might also be damaged by frost.

Temperatures above 86 degrees Fahrenheit (30 degrees Celsius) can cause heat stress. It probably won't surprise you to learn that we want our weed plants to be as chilled out as possible.

Soil Temperature

The soil is just as important as the air. It's where your plant's root zone is. The roots are how your weed takes in water and minerals, both crucial to growth.

Ideally, your soil should be a little cooler than the air. Something between 16 and 20 degrees Celsius is perfect.

Lower temperatures can make roots unhealthy. In turn, that can make them grow slower or even damage them. Damaged, unhealthy roots mean a smaller, slower-growing, and potentially dead plant.

You can probably guess that higher temperatures can cause heat stress. We don't want any part of our precious plants to feel stressed, so try and stick to the ideal temperature range.

Avoid Temperature Extremes

It would be impractical to keep your soil and air temperatures exactly constant throughout the growing season. That's why we've provided ranges. Some variation is fine.

Straying too far beyond those ranges, though, is dangerous. Temperature extremes, both high and low, are the bane of any indoor grower.

Monitoring Temperature

A thermometer or any other ambient temperature sensor is fine to measure air temperature. Just ensure it's away from anything that will cause an incorrect reading, like grow lights, direct sunlight, or heaters.

Ideally, position your temperature sensor in line with the top of your plants.

For soil, use a probe or thermocouple. Insert it about three inches below the surface of the soil.

For the more involved plant parent, an infrared sensor can be used to determine the exact temperature of the leaves.

Fortunately, there are entire monitoring systems available for the less involved plant parents among us. Higher-end monitoring devices can even adjust the temperature in your grow room in real time.

What does that mean? Well, if a mild winter or early spring means strangely warm temperatures, your plants could be in danger. You'd have to lower the temperature inside somehow, or let your monitoring system do it for you.

How to Heat Your Indoor Weed Plants

If you're growing through cold winters as a hobby, a simple heater could be all you need. High-quality grow lights sometimes also emit enough heat to keep your plants warm.

Keeping the roots warm can be a little trickier. Heat mats are your friend here. However, don't rely on them to maintain air temperature.

Insulating Your Weed Plants

Indoor growing isn't as simple as placing a heater next to your plants and assuming that'll protect them from the cold weather. That wouldn't be particularly energy efficient.

Instead, winter cannabis growing requires some insulation. This could mean a greenhouse. It could also mean a grow tent. 

A grow tent is great for growing inside an existing structure, like a room in your house or a garage. But if you're growing indoor plants outside, you'll probably want to invest in a greenhouse.

Take care to choose a greenhouse made of a good material. Twin-wall polycarbonate is a great choice. Insulated metal and curtains can be added in particularly cold climates. 

If you're expecting snow, ensure your greenhouse is also structurally sound. A sloping roof will protect your winter crop from the elements and prevent a buildup of snow from collapsing the whole structure.

Humidity Control

Excess humidity is the bane of plants indoors. It can cause bud rot, and generally result in sickly plants.

Normally, exhaust fans are enough to control humidity. But in cold weather, these fans can wreak havoc, blowing cold air all over your precious plants.

Instead, those looking to grow cannabis in colder climates should consider investing in an airflow system. There are two main types:

• Horizontal airflow systems: These circulate air throughout your grow space. This distributes the heat and moisture, removing any humidity trapped in pockets of stagnant air.
• Vertical airflow systems: These also circulate air, but specifically from the top to the bottom or vice versa. This is important because hot air rises. By constantly switching it with the cooler air below, these systems maintain temperature and humidity.

Ideal Humidity Levels for Plants Growing indoors

Once again, this depends on the growing stage of your plants.

During the vegetative stage, somewhere between 40% and 50% is ideal. Once your plants are flowering, aim for humidity levels between 30% and 40%.

How to Increase or Decrease Humidity

If your humidity levels are still too high, consider investing in a dehumidifier.

In turn, a humidifier can help you increase the humidity in your grow space if needed.

Managing Light 

Remember, we want to replicate the conditions our weed plants would experience when growing outdoors. During an outdoor grow, the sun does this for us.

Inside, it's up to us to regulate light. On the one hand, you'll likely need to invest in some grow lights to ensure your plants are receiving sufficient light intensity.

That's because the sunlight during winter is weaker than during the summer months.

However, this doesn't mean your plants want constant light. During the vegetative stage, between 18 and 20 hours is perfect. But once your plants are flowering, ensure they receive 12 straight hours of darkness.

This darkness isn't just for fun. The light cycle spurs bud development. After all, we want our weed plants to produce buds!

Other Things to Consider

Colder temperatures often mean lower temperatures and humidity. In turn, this often means your plants need less water. 

Your plants might also require different nutrients than if they were growing outdoors during the normal season.

Remember to regularly check the entire plant for signs of rot, mold, pests, or other undesirables.

Conclusion

It's totally possible to grow weed in cold climates. Even the harshest winter is no match for the prepared grower, armed with a proper grow room. By following the above tips, you can ensure high indoor yields.

Then again, you could always just order your flower online if this sounds like a hassle! At Clean Remedies, we use hemp sun-grown by local farmers in Oregon. This ensures that our products are only made with high-quality hemp, giving you the comfort you need to live a healthier and happier life. 

Keep Reading: Can You Freeze CBD Oil?

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