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Is cold bad for cannabis seeds

Outdoor Marijuana Temperature Range: Ideal, Okay, Extreme

Not sure if your climate supports outdoor cannabis growing? Find out how low temperature and cold weather affect your harvest

If your climate is too cold (like mine), or too hot, and you think that the only option for you is indoor cultivation, think again. The acceptable outdoor marijuana temperature range is quite wide, and marijuana plants, at least mature ones, can be surprisingly hardy. As a result, they can take a lot of bad weather and still reward you with enough high-quality buds.

Table of Contents

Ideal Outdoor Marijuana Temperature

Well, ideal outdoor marijuana temperature is actually the same for any type of grow. It’s because indoors we simply try to recreate artificially the natural environment that cannabis plants have best adapted to. The only difference is that, in an indoor setup, we have more control in maintaining the perfect conditions. And they are:

77-86°F (25-30°C) during the day, or when the lights are on.

At least these are the figures that are the most conducive to photosynthesis and gas/water exchange processes, according to research 1 . And, in case you’re wondering, the ideal level of light intensity (PPFD) would be ~1500 μmol/m2/s.

All this may guarantee the fastest rate of growth for cannabis plants. However, our goal is a bit different — we grow for the highest possible production of THC and other cannabinoids, as well as terpenes that make the smoke so aromatic and flavorful. So, with that in mind, growers have gradually come up with the following empirical figures:

  • Seedling and vegetative stage. Young weed plants prefer a little milder conditions than the flowering ones, with day temperature between 70 and 85°F (20-30°C).
  • Flowering stage. When plants start to form buds and then all the way to harvest, the temps should be a little lower — 65 to 80°F (18-26°C). The reason is that higher temperatures burn terpenes and cannabinoids making the buds less aromatic and potent.

During any stage of growth, the night temperatures should be 10°F (8°C) lower than during the day. This gives marijuana plants a chance to shift to a lower gear and have a rest. However, too radical a change between day and night temperatures can lead to even more stress, and should be avoided.

That Was Ideal, But What is Acceptable?

Outdoors, we work with what we have. Even in climates that give us the luxury of the perfect outdoor marijuana temperature range there are spells of too cold and too hot weather. So the question is: what is okay for outdoor weed and what is not?

Just like a dashing bachelor in a Jane Austin novel who chooses himself a wife, anything from 15 to 30 would do just fine. (Sorry for this potentially offensive remark, but in my experience they are the most memorable.) These figures are in Celsius btw, and in Fahrenheit it’s 59° to 86°.

At higher temps, no irreparable damage is done, although the photosynthesis slows down. And so does the THC production, while terpenes evaporate from buds at a faster rate, robbing them of flavor. The texture of buds deteriorates as well, and they become less compact and more airy.

So if you live in a really hot climate, like Arizona or Nevada, try to mitigate the effects of heat stress. Make sure that trees, walls or other structures provide some shade for your marijuana during the hottest hours in the afternoon. Or stretch some shade cloth over your garden (60% transparency should be just fine). Anyway, if higher temps may hurt weed plants, they can’t kill them. Drought can though.

The effects of cold temps are much worse. When the daytime temperatures drop below 15°C (59°F), all processes slow down to a crawl or are put on pause. And at 13°C (55°F), more delicate strains may experience a shock. It means that once the temps are back within the acceptable range, the plants will need some time to recover before they resume bud production.

The Effects of Frost and Snow

Below freezing air temperatures don’t kill marijuana overnight, but they can do a lot of damage to leaves, flowers, and even branches. They wilt and get brown and mushy in places, so if there’s a chance of snow or even a couple of frosty nights in a row, it’s best to harvest your buds before that.

These buds might be still salvageable, but the quality will be very subpar, to say the least.

I myself once harvested a couple of bushes after a heavy snowfall. They started to flower extremely late, so I had to push the limits with them. When I was cutting the branches, I had to shake them very hard to free them from snow. Only a minor percentage of buds were spoilt beyond being usable, but the rest turned out okay. I don’t recommend this to anyone, though. It’s safer to use a faster-flowering variety or an auto.

How to Protect Cannabis from Cold

1. Choose Genetics Wisely

Start with choosing a strain that is fast enough to finish flowering before the end of the growing season. The only sure thing are autoflowers because in practically any climate there are a couple of warm months in the middle of summer, and it’s all an auto needs. Besides being very quick to finish, autoflowers are more resilient to cold weather: they have Cannabis ruderalis genetics in them, and ruderalis is a subspecies that originated in places like Siberia and is very tolerant of cold.

This is a natural ruderalis plant. Looks pathetic, doesn’t it? Luckily, modern autoflowers are so much better in every respect.

If you prefer to grow a photoperiod variety, look for strains with words ‘fast’, ‘early’ or ‘quick’ in their names. They are the result of crossing a true photoperiod strain with an autoflowering one. These plants still wait for the days to become short enough before they start flowering, but this happens much earlier.

Important! When shopping for an outdoor photoperiod strain, take with a grain of salt the harvest times that a breeder promises. If, for example, they say late September, they probably mean places like Spain or Southern France, not Scotland or Denmark. The farther up north, the longer the summer days, and the later the flowering begins (and finishes). That’s a ‘perk’ of living at higher latitudes.

2. Find a Good Spot

The second most important thing is finding a spot that receives as much sunlight as possible and is sheltered from wind. It also helps to plant your cannabis near a wall (preferably a stone wall) that shelters it on the north side and is warmed by the sun. And by all means avoid planting your cannabis in a low spot. The thing is that cold air tends to ‘roll down’ from higher places into depressions in the ground, and then stays there. A south-facing slope makes for an ideal spot for your outdoor garden.

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3. Using Pots Increases Mobility

Another trick that’ll help you make the best of your cold climate is growing your outdoor marijuana in pots rather than in the ground. In this case, you can move the pots around, always choosing the sunniest and warmest spot and even take the plants inside if their very survival is under threat.

4. Start Seedlings Indoors

Keep in mind that, while mature plants don’t mind some cold weather, young seedlings do. They may be shocked or killed if the temps are outside the acceptable range. So make sure that summer weather has come for good—no ground frosts in the early morning and at least 15°C (59°F) during the day—before taking the seedlings outside. Also, it’s recommended not to sow cannabis seeds directly into the ground. It’s best to grow them for 2 weeks inside, then harden them a bit by taking outside for a couple of hours every day, and finally place them permanently outdoors.

Outdoor Marijuana Temperature: Focus on the Root Zone

One thing that is overlooked by most growers is that the temperature of the air plays a far less important role than that of the medium. The air may be as cold as 5°C (41°F), but marijuana plants will thrive if the temp in the root zone is at a comfortable level 2 . It’s like when you are neck-deep in a hot spring, you don’t mind that your head is exposed to a chilling breeze, right?

Remember all those numbers we’ve given above? They all apply to the root zone.

This really gives you a lot of freedom. The most obvious choice is to use a really thick layer of mulch to insulate the ground from the air. It works both ways, by the way: by keeping the ground cooler in hot climates, or keeping it warmer in cold ones.

Or you can go high-tech. A pump, a water tank with a heater/cooler and some clever piping laid in the ground or through the containers/grow bags will allow you to circulate water with a set temperature to warm up or cool down the medium. (And mind you we’re not talking about watering here, right? Watering is a different story. This is only about heat exchange.)

Also google ‘geothermal greenhouse’. This is basically an underground (or partially underground) greenhouse with a glass roof that is generally made sloping and facing south. A geothermal greenhouse makes use of the fact that deep below the ground surface the temperature remains stable throughout the year. It’s much cooler in summer, and much warmer in winter compared to above ground. For such a greenhouse to really work its magic the depth must be 10-12’ (~ 3 meters).

Outdoor Winter Grow

Wanna try and grow marijuana in winter? First check if your climate supports this idea. Again, the temperature, especially in the root zone, should be above 15°C (59°F) most of the time. Short periods of colder weather are unwelcome, but acceptable. Opt for cold-resistant strains, like Indica autoflowers. Also, use all the tips and tricks of protecting your plants from cold that we’ve shared above. And again don’t forget about the importance of the root zone).

Also keep in mind one more thing about marijuana winter grows: the days in winter are short, and the nights long. This will make any photoperiod variety start flowering after just a few weeks from sprouts. It’s not unlike the ‘12/12 from seed’ method. This usually results in much smaller plants, so if you want them bigger, think about auxiliary lighting to make the days longer.

If you don’t use auxilliary lights to extend short winter days, any photoperiod strain will go into the flowering mode.

Conversely, if your winter cannabis doesn’t finish before spring, or more specifically before the spring equinox (March 20), days will gradually become long enough to disrupt the flowering. So make sure you plan your winter grow accordingly.

Outdoor Marijuana Temperature Range is Quite Inclusive

Outdoor horticulture of medical marijuana is feasible even in colder climates. Just learn to make the best of the most adverse conditions and choose a strain that is quick to finish and is tolerant of low temperature. And now, after the arrival of autoflowers, almost anybody can grow top-shelf buds outdoors.

Growing marijuana in cold climates? Yes, it is possible!

It’s true that the ideal season to crop the vast majority of cannabis seeds is when it is not particularly cold and the hours of sunshine are abundant (long photoperiod), helping its growth and proper development. However, cold temperatures should not prevent you from growing cannabis all year round. In this post we’ll give you some techniques to achieve it.

The most common period for growing marijuana is usually between the months of April-May (seeds germination), for the September-October harvest (this can vary depending on what planet hemisphere we live; the latitude and the season), since they are the months in which the weather is less hostile, and in the rest of the months, many are the self-growers who devote them, simply, to consume everything they harvested.

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The cold should not be an impediment to growing marijuana. In times when it is colder or in countries where the cold is present almost all year round, there is what is commonly known as the winter harvest.

And when we speak of cold, we are not referring to temperatures below zero throughout the day and for long periods of time, since in those places it is difficult for this plant to grow; we are referring to climates where temperatures are maintained at an average of between 5 and 10 degrees, as is usually the case in the north of most countries in Europe or North America, as well as countries such as China, Pakistan or northern India, where the cold is present along the year in some of its most mountainous regions.

Latitude and altitude is one of the most important aspects to carry out a good outdoor crop

It is precisely from these places from where provide some of the most suitable seeds to grow in cold climates or in cold seasons, understanding the cold, as we have said, climate conditions with temperatures below 10 degrees, does not mean continuous frosts.

Therefore, if some of the best seeds are provided from these countries to the current cannabis market, is because is really possible to grow cannabis during the cold season, taking into account that many of the genetics which can be found in the seed market, have been progressively adapted to European latitudes.

Certain aspects must always be taken into account, such as knowing well the climatic conditions of the place where we want to grow our seeds, and the type of seeds we are going to use, being this one of the key points to achieve the results we want.

Before we get fully into the advice on how to grow cannabis in cold climates, it is important to know that the seeds we grow during this period will not result in large plants, and as a result the production will be smaller, although we know it will be worthwhile.

If you are fed up of having to wait for warmer seasons to grow marijuana, we invite you to continue reading this post, as it will be very useful to improve your winter harvest.

How cold affects marijuana

For a long time and specifically in countries where it is not particularly cold all year round, as is the case in most European countries, a large number of marijuana growers devote to this task in the less hostile months of the year, i. e. those that range from April-May (germination and transplantation of seedlings and cuttings) to September-October (harvest), approximately, which is the time of outdoor harvest. The rest of the year, they devote to enjoying the production and prepare the next harvests.

Actually, the problem is not the cold. It is true that the cold slows everything down, but the important thing is that it is cold, among other things, because the solar radiation is not so intense, and because of the scarce number of sunlight hours (photoperiod).

We at PEV Grow would like to encourage anyone who wishes, but does not dare, to try out winter crops, because it is possible, especially if we take certain aspects into account:

-The photoperiod is ideal for flowering: This means that our plant will start to bloom almost immediately. The best thing you can do is to grow the plants indoor until they reach a suitable vegetable mass, and then take them out to the garden (outdoor). The change to the natural photoperiod will do the rest. Do not forget to place the plants outdoors so that they have direct sunlight all day long.

-Smaller plants: Considering the previous point, it is logical that the plant we grow in winter does not reach a large size. In fact, it is estimated that they do not usually exceed 100 centimetres in height, but they can give us between 20 and 60 grams per plant. Although it’s not a good idea to do this with autoflowering plants, as these genetics will not have the photoperiod or the proper light intensity to provide an acceptable amount of vegetal mass.

-Try a greenhouse in the garden: Better an outdoor crop in glass greenhouse. This is the main recommendation to be taken into account when you decide to grow marijuana in winter, as this increases the size of the vegetal mass and is less likely to be invaded by pests. Humidity is also well controlled in this way, as plants are not exposed to the rainfall regime.

Greenhouse crops, better if glazed

-Grow Indica or hybrid strains: They are the ones that, in general, best adapt to this type of climatology. Later on we’ll give you some tips about choosing the best seeds for this kind of weather, but you can take a look at a longer article already published in PEV Grow previously which is about this topic. Sativa strains are better adapted to tropical climates, and therefore need a lot of light intensity.

Tips to combat the cold weather

As in everytime we grow cannabis,” Every grower have their own way to crop marijuana”, but we want to give you some general tip with guaranteed results in order to be able to carry out your marijuana crop during the winter or in cold seasons of the year.

-If we start from seeds: It is recommended to germinate them inside your home in any winter month. The germination is carried out with natural water, between 18-22ºC.

It is advisable to keep the seedlings indoor until the plant mass is adequate. In case they are cuttings, it is not necessary to take them out immediately, we can make them grow about 30 days. Watch out! As soon as we take our plants outdoor, the most normal thing for them is to start blooming, because they will notice a photoperiod shock.

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-If we use indoor lighting: Continuing with the previous point, and if we want to enlarge the photoperiod of the plant with the purpose of promoting its growth, we will have to use indoor lighting, as for example, LEC. In PEV Grow you can find a wide range of lighting equipment to help you getting the best results.

-Use pots: Especially if we grow outdoor and even though we are in a greenhouse in this case.

Why? Because plants that are directly grown directly in the soil are more difficult to give them heat, if the soil is not hot. However, the pot will avoid this problem.

Looking for pots? We have all kinds of grow stuff for you. In addition, we will improve our results if we place a cork or a piece of wood under the pots to insulate them even more from the cold.

We also have the option of using a “blanket” for the floor, made of heat-absorbing materials such as a limestone blanket. It is a technique widely used in vineyards, to dampen the temperature differences between day and night. If there is frost, we will prevent the roots from freezing.

-Be careful with the humidity! Although the truth is that during the winter, plagues are less common, humidity can always cause pest problems. We must bear that in mind. We must always use preventive fungicides, especially during the rainy season.

-Harvest staggered in time: It’s an interesting option, because if there were any unforeseen frost, we would not lose the entire crop, and we will have for longer time marijuana ready to harvest, we will be also able to crop in less space than if we were growing all the seeds at the same time. You should use to do it well an indoor germination and maintenance seedlings under indoor contidions.

Protect from cold to our marijuana plant

-Heater and thermostat: This option is only viable in greenhouses. For this reason, and in order to maintain all the time the temperature according to the development period in which our marijuana plant is located, it is best to place a thermostat on the substrate (substrate temperature) and greenhouse (temperature of the growing environment), to know what temperature we have at all times, and based on this, start a heater. If the substrate is very cold, do not forget to prepare the irrigation solutions by heating the water with a resistance, to leave it between 18 and 22ºC.

The best varieties for cold climates

As we have already mentioned above, the best seeds for growing in cold climates or in winter periods are the indica strains, since most of them come from hostile climates such as India or Pakistan, and their genetics come from pure acclimated landraces developed naturally in high mountain climates, where growth in itself is already quite difficult and therefore those landraces have become more resistant to fungal pests and cold along the time.

In addition, these seeds need less time to develop and, although they will not give large plants, the results will be good if we take into account the advice given in the previous section.

In PEV Grow you can find a wide selection of indica seeds, highlighting for example cultivars such as PEV Bank Seeds Critical Feminized, PEV Bank Seeds Mazar Feminized or PEV Bank Seeds Bruce Banner Feminized.

Bruce Banner causes in general cerebral effects givind us euphoric and creative notes which spread in the body providing a state of well-being…

Características
Bank: PEV Bank Seeds.
Type: Feminized.
Phenotype: Stabilized Bruce Banner F3 hybrid
Flowering period: 8-10 weeks.
Genetic: Og Kush x Strawberry x Diesel.
Indoor production: 350-500 gr / m2
Outdoor production: 500-650 gr / plant
THC level: 22.0-27.5%
CBD level: 0.03%-0.06%

PEV Bank seeds offers you the best genetics in the market at incredible prices, with Indica and Hybrids strains, acclimated to European latitudes with Mediterranean and Continental climates.

Other ancestral genetics of Indica phenotype, highly valued by our best breeders are cultivars such as Sensi Seeds Afghani 1, Dinafem Blue Hash, Dutch Passion Mazar and Sweet Seeds S. A. D.

It is a great producer outdoors, due to its size, and a good choice for high altitude mountain areas, where cold nights give it attractive colours…

Características
Bank: DINAFEM SEEDS
Sex: Feminised
Genotype: Blueberry x California HashPlant
Phenotype: Indica-Sativa, with dominance indica
High: about 3 metros.
Growing time: 56-70 days
Resistance to mushrooms: High
Resistance to plague: High
THC Level: 12%

Conclusion

As you can see, it is also possible to grow high-yield cannabis under “unsuitable” conditions. Simply select the seeds carefully and take special care with the plant.

The Mediterranean is the most favourable climate for growing cannabis outdoor, especially in its flowering phase, although it carries an artificial irrigation calendar. But in cold climates it’s also possible to grow marijuana and, without going any further, here is the example of Dutch marijuana, where breeders have been grown during three decades the most powerful Indica marijuana genetics and hybrid phenotypes fundamentally.

At PEV Grow, you have a large collection of feminized seeds to ensure a good harvest, the best quality, and also make you save money.

And in case you don’t dare to do a winter crop, in other posts we will try to work entirely indoor, mentioning the best tips for your indoor crop.

And if you have dared, please share your experience, and tell us what strain you’ve grown explaining us what were conditions you used and if you applied any of our advices.