LED Growers Need a Heater in Winter: Lights, Root Heat Mats and Greenhouses for the Cold Season

Growing cannabis plants indoors in winter mostly comes down to heat and humidity: LED grow lights run cool, so in a cold room they often can't keep the temperature up on their own, and you'll likely need a heater plus a dehumidifier to keep mold away. Cold-hardy genetics, warm roots and good airflow do the rest. Get those right and you can pull a big, high-quality harvest even in the coldest months of the year.

That means holding the right temperature, managing relative humidity and giving the plants enough artificial light as the temperature drops and daylight hours shrink. Ventilation matters too, to head off mold and pests, which can thrive in colder, damper weather. With the right techniques and gear, you can create a controlled environment that mimics ideal growing conditions.

Indoor growing: pick the right genetics

The success of any indoor cannabis grow depends a lot on the plants' genetics. When you're planning a winter grow or growing in a cold climate, choosing the right genetics is key to a good harvest. Strains adapted to cold climates, like indica-dominant varieties and landraces from the mountain regions of Asia, tend to handle low temperatures and rough conditions better.

Autoflowers are also a great option for growers in cold regions. Derived from Cannabis ruderalis, a subspecies found in Central and Eastern Europe and Russia, these plants are known for being tough. Plus, their fast life cycle, which can wrap up in just eight weeks from seed to harvest, makes them ideal for squeezing in extra harvests in early spring or late fall.

Starting with the right genetics doesn't just boost your odds of a successful harvest; it also makes the plants easier to manage through the whole grow, especially when conditions get tough.

Can you grow weed outdoors in winter?

Growing weed outdoors in winter is a real challenge, and in most cases it's not a good idea. Unless you live somewhere with unusually mild winters and little rain, you'll probably run into serious problems, like sick plants and low-quality harvests.

Tips for growing weed outdoors in winter

If you decide to give an outdoor winter grow a shot anyway, here are some tips to boost your chances and keep your plants in the best shape possible:

1. Keep the roots warm
   Use heat mats to keep the soil temperature above 12 °C (54 °F). That keeps stress on the root system down and makes for healthier vegetative growth and flowering. Warm soil can make plants a lot more resistant to cold and help them develop properly.
2. Protect your plants from rain and snow
   Moisture trapped in leaves and buds can lead to serious mold problems that are hard to control and can wreck your harvest. Covers or protective structures help keep rain and snow off your plants, cutting the risk of fungal infections and moisture damage.
3. Keep an eye on your grow dates
   If you grow outdoors, watch the outside temperatures closely and move your plants indoors before the weather turns too harsh. That protects them from extreme temperatures and keeps the hard cold from doing damage they can't recover from.

Bottom line: an outdoor winter grow is possible with the right precautions, but the conditions usually make it less viable than growing indoors or in a milder climate. A controlled, protected environment is the key to a successful harvest any time of year.

Growing weed in a greenhouse: pros and things to consider

Growing weed in a greenhouse is a great solution if you want to grow year-round, no matter what the weather's doing outside. A well-run greenhouse gives you precise control over key factors like light, temperature and humidity, which can mean successful harvests in any season.

That said, there are a few things to weigh before you jump in.

Pros of growing in a greenhouse

1. Full control of the environment
   A greenhouse gives you a controlled environment where you can adjust light, temperature and humidity to dial in your plants' growth. That lets you grow year-round, even in cold climates or in winter, so your plants get the conditions they need to thrive.
2. Free solar power
   If you live somewhere with plenty of sunshine, a greenhouse lets you tap into that natural energy. The sun can be a cheap light source for your plants and cut the electricity costs that come with growing indoors.
3. Privacy
   A greenhouse can give your plants more privacy than an open backyard, which comes in handy in residential areas where visibility can be a concern.

Things to consider before choosing a greenhouse over an indoor grow

1. High upfront costs
   Building and setting up a greenhouse can be a serious investment. Startup costs are usually higher than setting up a grow room or grow cabinet indoors. Plan and budget carefully so you can cover those costs and keep the greenhouse running long-term.
2. Upkeep and management
   A greenhouse has a lot going for it, but it also takes careful management to keep conditions dialed in. You'll need to stay on top of ventilation, humidity and temperature to prevent problems like mold and pests.

All in all, growing weed in a greenhouse can be a great option if you want flexibility and want to make the most of natural sunlight. Just factor in the upfront costs and the upkeep to make sure the investment pays off and your plants stay healthy all year.

Why the new generation of growers will need heat in winter

LED lighting is quickly winning over millennial weed growers, overtaking traditional HID (high-intensity discharge) bulbs. But for all their advantages, LED setups come with some challenges in cold climates that may call for extra heating in winter.

The trouble with LEDs in cold weather

1. LEDs run cool
   LEDs are known for their energy efficiency, turning close to 75% of the energy they draw into visible light. That cool running is usually a plus for climate control in a grow cabinet. In winter, though, it can backfire, because LEDs don't put out enough heat to keep the grow space at the right temperature.
2. A hit to your energy savings
   Having to run a heater to make up for how cool LEDs run can eat into the energy savings they give you. That extra power use can cancel out some of the cost advantage of LEDs over HIDs.
3. Relative humidity problems
   LED setups can also add to humidity problems in cold weather, since low temperatures plus high humidity invite mold. To cut that risk, add a dehumidifier, especially during flowering.

The trouble with other indoor grow lights in cold weather

1. Fluorescents fall short
   Fluorescent bulbs, even high-wattage ones like 300 W, don't produce enough heat when it's cold. That makes them unreliable in winter, since they won't keep the temperature where your plants need it to grow.
2. Rot risk
   Hydro systems and LED grows can both run into bud rot and root rot if you water with water that's too cold and relative humidity goes over 60% during flowering. Put those two together and you're putting plant health and harvest quality at risk.

Tips for growing weed in winter

1. Keep tabs on the environment
   Tight climate control all year round is essential. Check your thermometers and adjust the heat as needed. Heating a grow room in winter may be easier than cooling one in summer, but managing temperature properly is still key to healthy growth.
2. Use your lights strategically
   Growers running HIDs can take advantage of the heat the bulbs give off by running them during the dark hours on cold nights. That helps keep temperatures more stable. LED fans, on the other hand, may need to keep a heater on a steady schedule to keep things warm.
3. Mix your lighting
   A combo of HID and LED can hit the sweet spot, giving you both efficient light and the heat you need in the cold months. It can dial in your grow environment and keep plants healthier.

A bonus of growing indoors in cold weather

One upside of growing weed at low temperatures is that some strains can show lilac and purple hues, a look a lot of growers and smokers love. That can add extra value to your harvest and make the extra effort on climate control worth it.