Cannabis plants love warm and sunny locations, but does this mean that you cannot plant marijuana seeds in the winter? Not necessarily: your chances of How cold is too cold for cannabis? Whether that’s indoor or outdoors, growing cannabis in cold climates present extra challenges you'll learn to overcome in this guide.
How to plant marijuana seeds in winter
Cannabis plants love warm and sunny locations, but does this mean that you cannot plant marijuana seeds in the winter? Not necessarily: your chances of success will depend on what the winter season is like where you live. Outdoors, low temperatures and lack of light make the process especially difficult, so yields tend to be smaller. Fortunately though, thanks to the advancements in indoor techniques, it is now possible to grow all year round in the comfort of your own home.
In countries closer to the tropics, where temperatures are quite mild even in the winter, it is possible to grow marijuana outdoors all year round. However, at latitudes that are further from the equator, cannabis doesn’t often develop properly outdoors in the winter, especially in snow or freezing conditions. Even though some strains can withstand lower temperatures better than others, warmth is the key if what you’re looking for is high-quality weed.
Once the temperature drops below 15ºC, the metabolism of cannabis plants gradually slows down as their biochemical and enzymatic processes become paralysed. Under these circumstances, their root system doesn’t expand as it should, which means that the plants cannot absorb as many nutrients as usual, which in turn leads to highly unproductive growth.
So ultimately, if you want to plant cannabis seeds in the winter, you need to evaluate the pros and cons of indoor growing versus outdoor growing, and then decide which one better adapts to your needs. Here are some basic tips for successfully planting marijuana seeds in the winter:
1- What cannabis seeds should you plant in winter? Choose the right strain.
Some marijuana strains work better than others in colder climates. Look for indica-dominant varieties from those parts of the world that tend to be cooler, as these have adapted more effectively to the difficulties of living in the open. Sativas originate from tropical regions with warm and humid climates, so they struggle more than the indicas in cold environments.
Our seed catalogue includes several options that are worth considering:
- CRITICAL GENETICS: Kritikal-k
- WIDOW GENETICS: Feminized Silver Widow
- SKUNK GENETICS: Feminized Skunk+
- KUSH GENETICS: Purple Kush, Og Kush
Of all the possible options, autoflowerings are usually the most suitable. Thanks to their ruderalis heritage, which derives from regions like Siberia, these cannabis plants have adapted to adverse climate conditions and to the different day and night durations with minimum resources. As a result, they are more resistant to the cold and don’t depend on the photoperiod to start flowering, which makes them much easier to grow in the winter.
Here are some highly resistant varieties that will definitely solve any doubts about which autoflowering seeds you should plant in winter:
- GINGER ALE GENETICS: Ginger Punch Auto
- CRITICAL GENETICS: Kritic Auto
- XL GENETICS: Amnesia Dream XXL Auto
Indoors: Regardless of the type of seed, the temperature for germination must remain between 22ºC and 25ºC, with a relative humidity between 70% and 90%. These conditions can be difficult to achieve unless you grow indoors or use a mini greenhouse. We recommend keeping your seedlings indoors until their vegetable mass has grown substantially and their root system is extensive enough for them to feed through it.
2- Keep an eye on the root system as it is the one that suffers most from the cold.
The health of the root system is vital when you’re planting seeds in the winter, especially during the seedling phase. When outdoor cannabis is grown in pots, the root area can get very cold. Plants that have rooted directly into the soil cannot be moved, but their roots will stay much warmer than in a pot during a cold night.
Top tip: during the hours of darkness, outdoor plants can be covered with plastic sheets to help them retain the heat. In any case, it’s always best to shelter them in a greenhouse if you have one available.
Indoors: LED lighting can be highly efficient, but HPS technology has a major advantage in winter because it produces a lot of heat. If you have a cold grow room, an HPS light can have a double function as a source of both light and heat for your plants. However, you should always take into consideration the temperature of your grow room when the lights are off.
3- Keep a constant temperature to prevent thermal stress.
The optimum daytime temperature for cannabis is between 24ºC and 29°C, whereas the optimum night temperature ranges between 18ºC and 22°C. It is essential to avoid large contrasts between the two, as a constant temperature helps the plants optimise their growth, health, yield, and potential. In some areas the changes in temperature between night and day can be extreme, so using a greenhouse will help minimise this thermal contrast.
Indoors: If you grow cannabis indoors when it’s cold outside, it’s advisable to start the light cycle after sunset, when the temperature is lower. This way, the darkness cycle occurs during the day, when the temperature is higher, which in turn helps to prevent extreme changes in temperature.
4- Controlling the humidity levels: a double-edged sword.
It’s quite common to be confronted with rainy, frosty, or foggy conditions during the colder months. Besides, morning dew can appear, which creates the perfect environment for the development of mould and fungi. Find an outdoor grow space that gets a lot of sun in the morning and is protected from the prevailing wind. This will help the morning dew evaporate more quickly.
Indoors: Freshly planted marijuana seeds need between 80% and 90% relative humidity to germinate. Humidity is then decreased progressively to 60-70% during the vegetative phase. These parameters can be easily controlled through the use of air conditioning and dehumidifiers. However, indoor humidity is lower in winter than in summer, and in some cases can drop below the optimum range. There are several ways to correct this; for instance, by increasing intraction power so that more humid air comes in from the outside.
5- Be careful with overfeeding: less is always more.
Cold air tends to be drier, and the roots of the cannabis plants can compensate for this by absorbing more water. But this can be problematic if the seedlings grow in a substrate that is particularly rich in nutrients, as it can lead to burns on the tips of the leaves caused by overfeeding. But if the temperature drops too much, down to 10ºC or even lower, then the plants will struggle to absorb the nutrients effectively (especially phosphorus and magnesium). This is what is known as ‘nutrient lockout’.
Indoors: In this case, you must consider using a heating system or maybe some heating blankets to stop the root area from getting too cold. If you’re growing in hydroponic media such as coco coir, remember that with feeding ‘restraint is a virtue’: you can always resort to foliar fertilisation if you’ve fallen short.
As you can see, planting marijuana seeds in the winter doesn’t need to be an odyssey if you follow our advice. With some advance planning you can prevent plant issues and guarantee a successful harvest. We encourage you to check it out for yourself!
Kannabia Seeds Company sells to its customers a product collection, a souvenir. We cannot and we shall not give growing advice since our product is not intended for this purpose.
Kannabia accept no responsibility for any illegal use made by third parties of information published. The cultivation of cannabis for personal consumption is an activity subject to legal restrictions that vary from state to state. We recommend consultation of the legislation in force in your country of residence to avoid participation in any illegal activity.
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Top 10 Tips for Growing Cannabis in Cold Climates
Can weed grow in cold climates? Some growers worry at the thought of trying to grow cannabis in cold climates, whether that’s indoor or outdoors. Yes, cold climates present extra challenges for cannabis growers. But they also present some advantages and opportunities. You may find it easier to grow buds with hints of autumnal colours, or easier to prevent grow room temperatures from getting too hot, for example. With good planning and the right cannabis seeds, growing cannabis in cold climates isn’t merely possible, it’s quite straightforward and may even offer some surprising benefits.
Indoor weed growing in cold climates basics
Growing cannabis indoors can seem like the best approach if your climate is simply too cold and the outdoor growing season is too short. Indoor cannabis cultivation is a chance to avoid the worst of the early season and late season weather.
Although many consider it relatively easy to grow good quality cannabis indoors, there are some considerations when the weather is cold. If you are growing on a cold concrete floor, the root space of your cannabis plants will quickly find the heat drained from them. This can dramatically slow down growth, affect quality and cause issues with nutrient uptake if temperatures have dipped too low for too long. If your grow room is too cold results will be significantly below expectation and harvest quality may well be disappointing.
When growing indoors in a cold climate, consider which room to grow in. Perhaps, if you have the choice, you will want to avoid a room with too many external walls. This can cause the room temperature to drop further than you might like, especially during the ‘lights off’ period. You may also want to avoid trying to grow in the loft – this can also present problems with temperature extremes in mid winter when your lights are turned off.
That’s why many indoor growers grow autoflower seeds during the winter months. With 20 hours of daily light (or even 24 hours!) your grow light will be able to help keep the grow room warm. Though it’s worth adding that some of the latest and most efficient LED grow lights don’t produce much surplus heat at all. Older HPS lights, however, are less efficient and do produce plenty of heat which may come in useful during winter grows.
A Dutch loft grower got a nasty surprise when the snow melted on his roof and the neighbours called the police. Indoor growing in cold climates can present certain challenges!
Loft growing during winter can result in tell-tale signs of snow melt on your roof, causing paranoia and worry. You need to be aware of the risks. But the indoor grower, with some creative thinking, should be able to overcome the challenges of growing cannabis in cold climates.
Outdoor weed growing in cold climates basics
Can you grow weed outside in the winter? Maybe not in a northern European winter. But you can grow cannabis well in cold climates. Much depends on your climate and temperatures. If trying to grow cannabis indoors in a cold climate isn’t for you, then you will be relieved to know that plenty of outdoor growers have great success in cold outdoor weather. Lots of growers manage to grow cannabis in the cold climates of Scandinavia and Northern UK. Outdoor growers in Denmark have even managed to get two successive outdoor autoflower crops per year. The first auto crop is an early season harvest, the other is a late season outdoor grow. The following article explains more:
|Getting 2 outdoor auto crops in one season in Scandinavia. Cold climate outdoor grow guide|
Growing weed in winter may only be possible in tropical climates. But growing cannabis outdoors in cooler temperate climates requires the right outdoor cannabis seeds combined with a good understanding of the length of the growing season. You will need to maximise your plants exposure to the sun, choose a sunny and sheltered spot perhaps with some protection from the prevailing wind.
What temperature is too cold for plants outside? Plants will tolerate the occasional nighttime low temperatures of around 10ºC but not for extended periods.
You will also need to ensure that your plants are protected from pests such as slugs and snails as well as protecting them from other animals such as rabbit, deer etc. If you’re growing cannabis on your own land you will also want to choose a private location that isn’t easily overlooked by neighbours.
Ultimate checklist for growing cannabis in cold weather
If you live in a cold climate you need to evaluate the pros and cons of indoor cannabis growing vs outdoor cultivation and then decide which best suits you. To help, we have listed our top 10 tips for growing cannabis in cold climates.
1) Pick the most cold-resistant cannabis strains
There’s no point trying to grow tropical cannabis strains outdoors in unreliable, marginal conditions. Instead, you need to consider specialist outdoor cannabis strains that have been selectively bred over many generations. Selective outdoor breeding uses genetics from plants that have adapted well to the difficulties of outdoor life.
The Dutch Passion outdoor seed collection has been fine tuned for over 3 decades with some of the very best outdoor cannabis seeds, created specifically for outdoor growers at Northern European latitudes.
You may prefer to select outdoor indica strains rather than trying to grow a late blooming Haze/Sativa strain in a cold climate. Indicas tend to have shorter bloom cycles which better suit the short summers.
How to grow weed outdoors in winter?/Growing cannabis outdoors in winter? Unless you live in a climate with warm winters (such as a country close to the equator) it is simply impossible to grow cannabis outdoors with good results in winter months.
If the arrival of the cold autumnal weather arrives too close to the harvest date for your feminised outdoor strains, you may prefer to grow autoflower seeds outdoors. Autoflower seeds are often ready to harvest outdoors around 100 days after germination. The means that you can grow them outdoors even in the shortest of summers.
|Growing cannabis outdoors|
2) Maintain a consistent temperature
The changes from daytime maximum to night-time minimum temperatures can be extreme in some areas. The successful outdoor cannabis grower knows the importance of avoiding extremes and trying to maintain a consistent temperature. Once outdoor temperatures dip much below 15ºC growth rates tend to slow dramatically.
Outdoor temperatures of around 23ºC (around 73ºF) are ideal for outdoor cannabis growing. Temperatures of above 30ºC are best avoided, though in a warming climate that is difficult. Even Scandinavia has recorded summer temperatures above 30ºC in recent years.
Many outdoor growers make a google check to find out the average date of the last Spring frost in their area. Putting/planting your cannabis plants outside after the last frost is always best practice. The experienced cold climate weed grower may well choose to germinate his outdoor plants in the warmth and safety of the indoors until the last frost has passed. Then the plants can be gradually acclimatised to the great outdoors for a few hours per day before being permanently planted into the best outdoor grow location you can find.
|Cotton pads, the best way to germinate your cannabis seeds|
Growing marijuana outdoors in winter isn’t easy. Choosing fast blooming varieties is the best way to avoid the worry of a fast approaching cold season. One other way to maintain a consistent temperature is to consider a greenhouse or polytunnel.
Does frost kill buds? Yes, a severe frost will not just ruin the buds it may kill the plant completely. If you are trying to bloom outdoor plants in frosty weather it may be time to consider growing autoflower seeds or early flowering photoperiod feminised outdoor seeds.
How to grow weed outside in the winter? Growing cannabis in a greenhouse during winter is possible if you have supplemental heating and lighting. This is the technique used by Californian greenhouse growers. Without supplemental lighting and heat, the winter harvests would be substantially lower than the summer greenhouse crops.
Even without supplemental heating and lighting, a greenhouse (or polytunnel) protects your delicate seedlings from the worst of the early season weather. It also protects your precious buds from the worst of the late season cold weather. With consistent temperatures you help the plants to deliver optimised growth, health, yield and potency.
|Growing cannabis in a greenhouse|
3) Control humidity levels at all time
Temperature and humidity are always important when growing cannabis. But for those growing in cold conditions, it is especially important. Controlling outdoor humidity isn’t possible, but the expert outdoor grower is aware of the seasonal fluctuations in his local conditions and will factor this knowledge into the planning.
During late bloom, the danger of mold and bud rot is always a threat. In cold weather, morning dew can form on your outdoor blooms. This can lead to botrytis (bud rot/mold). Bud rot is one reason why many outdoor growers look to find an outdoor grow location with plenty of morning sun and preferable all day sun! Morning sunshine encourages the morning dew to evaporate minimising the chances of rot.
4) Beware of overfeeding your plant with nutrients
Correct nutrient management is one of the cornerstones of cannabis cultivation. Maintaining your plants in the nutrient sweet spot, without over-feeding or under-feeding is a skill that improves with experience.
Outdoor growers need to be particularly aware of some issues that can be seen in cold climates. That’s because cool air tends to be dryer and cannabis roots may compensate with greater water/nutrient uptake. If the soil is particularly rich in nutrients that can cause slight nutrient burn, often visible on the leaf tips.
If temperatures get too cold, around and below 10ºC, the plant will struggle to absorb nutrients and may be unable to absorb sufficient Phosphorus. This is known as nutrient lock-out, the necessary nutrients may be present but due to cold (or incorrect pH) the nutrients can’t be effectively absorbed.
Indoor growers that experience cold temperatures should consider additional heating or perhaps some electrically heated grow mats which prevent the root zone becoming too cold.
5) Keep an eye on your root-system development
Smart outdoor growers will often use specially bred outdoor seeds (or perhaps autoflower seeds) for the best results. In both cases, the health of the cannabis root system is paramount. When outdoor plants are grown in containers the root zone can get very cold especially in early/late season weather extremes.
Plants that are rooted directly into the ground may not have the benefit of transportability. But the roots will stay much warmer in the ground than they would in a container above ground during a cold night. If you have chosen your grow location well with all-day sunshine, the sun will warm up the soil which retains heat during the night for those plants rooted directly in the ground.
Cold roots simply can’t grow rapidly. If the root zone is left too cold for too long plant health will soon start to suffer and growth rates will slow. Indoor growers with plant containers positioned on a cold concrete floor will see the same issue.
|All you need to know about cannabis roots|
6) Choose the right lighting if you’re growing indoors
LED lighting may be all the rage, with optimised spectrum and longer life. But ageing HPS light technology does have one advantage – it produces a lot of heat. Often excess heat is regarded as a grow room problem. But if you have a cold grow room with cool external walls, an HPS light can perform the double function of lighting your plants and warming the room. Though be sure to consider grow room temperatures when the HPS lights are switched off.
7) Time your grow with accuracy
Just as loft growers may not want to consider a grow in the middle of summer, cold-weather growers also need to consider the timing of the grow and the temperatures that will be faced. For some growers, avoiding the summer heat problems can be a blessing. If your main issues are grow room temperatures getting too hot, then you may actually prefer to grow in the winter months. Conversely, if you know that it’s difficult maintaining grow room temperatures in the depths of winter, you may prefer to avoid growing cannabis in winter all together.
If you need to avoid the onset of winter, then growing autoflower seeds outdoors over the summer could be easier than risking an outdoor photoperiod grow which may not finish in time.
Use of greenhouses and poly tunnels can be essential for those growers that want to protect their plants form the worst of the early and late season weather. But if you can time your grow accurately and use early flowering outdoor seeds you can expect good results. The following article about a Danish grower who produces large plants in Scandinavia may be encouraging reading for those trying to grow weed outdoors in cold climates.
|Growing large cannabis plants outdoors in Denmark|
Are there cold weather autoflower seeds which will grow well in winter? Unfortunately not. Cold climate autoflowering seeds just don’t exist. Select the warmest and sunniest 3 month period of your outdoor growing season to grow your autos. Some outdoor weed growers have such short growing seasons they simply have no choice but to use autoflower seeds.
|Top 5 best yielding autoflower strains|
8) Learn to recognise your plant’s warning signs
Know the signs of a plant which is struggling to cope with poor outdoor conditions. The signs plants are too cold may include the following:
- Leaf edges start to curl
- Leaves turn yellow much faster and earlier than usual
- Growth can slow or even stop completely
- Leaves may brown and drop off, and the petioles (stalks which connect leaves to the stem) may turn brown
Knowing that your plant is in trouble is a warning sign to try to correct the situation, or avoid it in future.
9) Consider swapping your light and dark cycles
If you grow cannabis indoors in cold weather you may wish to consider having the ‘lights on’ period after sunset when ambient temperatures are coldest. This way, the lights-off period happens during your daytime when ambient temperatures are warmest. This helps maintain a more consistent temperature and avoids excessive temperature swings. In turn, this improves plant health and contributes to improvements in harvest quality.
10) Try force-flowering
If you’re growing photoperiod feminised cannabis seeds outdoors in a greenhouse you may want to consider greenhouse blackout blinds. These are used by many licensed greenhouse producers in legal grow environments such as the USA.
A blackout blind is used to force plants to flower in 12/12 light conditions even if the sun is shining outside. Using a blackout blind allows you to start 12/12 bloom conditions in early summer if you wish. It’s a great way to avoid the coldest temperatures later in the season.
Force-Flowering also has the benefit that you can select other, perhaps heavier yielding, cannabis strains which might not otherwise finish before the winter weather arrives.
|Top 5 fastest growing cannabis strains|
The following Dutch Passion strains have all been grown successfully by growers with challenging growing climates and cold weather. For those with the very shortest growing season, autoflower seeds are highly recommended.
Top 5 strains to grow in cold weather
Frisian Dew feminised (Dutch Outdoor)
Frisian Dew is one of Dutch Passion’s best selling outdoor cannabis seeds with literally thousands of repeat growers. She grows well as far north as Denmark/UK and tends to be ready for harvest around the start of October. Frisian Dew seeds are part of the Dutch Outdoor Seed Collection.
Auto Mazar (Afghani Kush)
Auto Mazar is a tough and hardy strain, part of the Dutch Passion Afghani Kush cannabis seed collection. Outdoors she takes around 100 days from seed to harvest. She often reaches around 75-100cm in height. If your growing season is very short, even for autoflowers, you can always consider germinating the Auto Mazar seeds indoors and keeping them there for a couple of weeks before placing them outdoors permanently. This way, the plants are protected from the weather/pests while they are at their most vulnerable.
|Auto Mazar growing outdoors in a cold Welsh summer|
Hollands Hope feminised (Dutch Outdoor)
Hollands Hope is another member of Dutch Passion’s cannabis cup winning collection of Dutch Outdoor cannabis seeds. It’s a large yielding indica with high THC levels and good mold resistance. This strain was bred outdoors in Holland and is a reliable outdoor photoperiod feminised seed which is fully proven over many years.
|Holland’s Hope outdoor grow review in Canada, mold free harvest!|
Auto Duck (Dutch Outdoor)
Auto Duck is an autoflower seed which performs very well in cold climates with short summers. She takes around 100 days from seed to harvest and is another solid autoflower choice for outdoor growers. One added advantage of Auto Duck is that she grows with a stabilised leaf deformity. This gives her natural stealth, you could walk past an Auto Duck and not realise that it’s cannabis! It’s a useful additional feature to a popular outdoor auto strain. The photoperiod feminised seed version called Frisian Duck is also highly recommended for outdoor growers in cold climates.
|Auto Duck grown in a polytunnel|
Durban Poison feminised (Dutch Outdoor)
Durban Poison is a photoperiod feminised seed variety with a great reputation amongst outdoor growers. Outdoors, Durban Poison seeds can grow to around 2m tall in typical conditions and is ready to harvest in early autumn. Just like the other outdoor cannabis seeds mentioned, Durban Poison is hardy and robust with solid yields and particularly strong buds.
Durban Poison is another member of the proven Dutch Passion Dutch outdoor seed collection with high THC levels and robust outdoor performance.
|Durban Poison and Frisian Dew grown outdoors in Wales in a cold, damp summer|
Specialist High Altitude cannabis seeds for cold climates
One other successful strategy used by those that grow cannabis outdoors in cold climates is to grow specially developed High Altitude cannabis strains. Such varieties have been selectively bred at high altitude. One by-product of these tough high altitude strains is that they are also particularly well adapted to cold weather. Many of those that grow these high altitude strains remark at how well the plants cope with particularly cold night temperatures.
Dutch Passion undertook some selective high altitude cannabis breeding in the Swiss Alps during the 1990’s. The best performing genetics were selected over several generations until two stand-out strains emerged, Snow Bud and Pamir Gold. Today, both these strains are relied on by many that grow their cannabis in high altitude locations such as the Alps, Pyrenees, Sierra Nevada and Caucasus. If your usual strains simply struggle to cope with the temperatures at your grow location then maybe growing some Snow Bud seeds or Pamir Gold seeds is the best strategy for you.
Can weed grow in cold weather?
Yes, cannabis can be grown in cold climates. But do your preparation well, know when the last frost of spring and the first frost of weather are likely to arrive at your grow location and plan accordingly with some early flowering outdoor cannabis seeds.
Understand whether you are more likely to succeed with autoflower seeds or feminised seeds, and remember you can germinate and grow your seedlings indoors if the early season weather is unpredictable. Good luck with your cannabis cultivation, don’t let cold weather stop you!