Germinating weed seeds in winter

How to Grow Cannabis in Winter

If you think that growing cannabis in a European winter is impossible, then you’ve been misinformed. With the right conditions in an indoor growing operation, you can successfully yield good quality cannabis. We are here to teach you how to set up and optimize your grow room in the winter time.

When growing cannabis in winter, even an indoor garden is at the mercy of the elements. Cold, dry air and dropping temperatures can create problems with relative humidity and light intensity. But that doesn’t mean that growing in winter is impossible. Actually, with the right conditions, an indoor garden can perform just as well in winter as it does in the summertime.

It is true that growing in the winter takes a little more attention and a little more TLC. With the right advice and the right frame of mind, you can successfully grow all year round. That is what we are here to help you do!

How to maintain grow room temperature in winter

Temperature is one of the most important concerns when growing in the winter. Optimal daytime temperature for cannabis is 24-30°C (75-86°F), and optimal night-time temperatures falling in the range of 18-22°C (64-72°F).

As a grower, you want to avoid temperatures outside of the prescribed range but you also want to avoid huge discrepancies between day and night temperatures. Growth rate is severely affected by inconsistent temperature changes as much as by an incorrect temperature bracket.

As well as this, if there is too great a discrepancy between daytime and night-time temperatures in the first 2-3 weeks of the flowering period (during which time plants ‘stretch’ noticeably), very widely-spaced internodes will result. Conversely, keeping the discrepancy as small as possible throughout this time reduces the space between nodes.

A temperature gap of 2-4°C (3.6-7.2°F) is ideal for the first 2-3 weeks of flowering. A gap of no more than 10°C (18°F) should be maintained for the rest of the flowering period.

If you are an old-school cannabis grower, then you probably love growing in the winter. That is because last decade’s HID (high-intensity discharge lightning) technology emits alot of heat. And if you are using them in the summer time, then you need to pay through the roof for air conditioning. But in winter, HID lights can keep your grow room at the optimal temperature.

With that being said, a temperature drop when the lights are turned off is something to think about. To mitigate this, winter growers use their lights during the night time and use daytime as the lights off period. This lets a grower take advantage of warmer temperatures during the day.

While daytime temperatures are higher, they are not always high enough to maintain the plants’ required ‘night-time’ temperatures of 18-22°C (64-72°F). If temperature is consistently dropping below this range when lights are off, it is advisable to use central heating or an electric heater to maintain adequate temperatures.

A digital thermostat will come in handy here to automatically control the heater according to the ambient temperature. If using cold lights such as LEDs, heaters may be required round-the-clock.

Controlling humidity of cannabis grown in winter

Mould is one of the biggest threats to your cannabis garden during the winter. In the winter, there is a tendency for low temperatures to increase relative humidity (RH) to a point of danger for your plants. Not only do cannabis plants detest high levels of relative humidity, but it also makes them a breeding ground for mould and fungi. Low temperatures can create issues in maintaining relative humidity.

Essentially, the volume of water in the air continues to condense as the temperature drops. And if you have ever grown cannabis before, you know that this can open up a proverbial can of worms (or better yet, mould) all of your plants.

The obvious way out of this problem is to keep temperatures at the optimum level, whether by using lights or by using central heating. If the problem is extremely hard to contain, then it may be necessary to use a dehumidifier.

It is also highly recommended that winter growers purchase a device called a hygrometer. This device can test the relative humidity of your soil as well as your grow room. It is essential to regularly measure the relative humidity in order to stay on top of it and avoid huge spikes or drops in the concentration of water in the air.

In many areas, winter is actually the driest time of the year, as well as being the coldest. If you are not facing issues of relative humidity, then cold dry air will present problems of its own in the grow room. If air is taken in from outside at a temperature of 10°C and an RH of 50%, it will contain water vapour at 4.7g/m³. If this air is heated to 25°C without the addition of extra moisture, its RH will drop to around 20%, which is far too low for healthy cannabis plants to grow.

In the growroom, a moist growing medium along with transpiration will generally raise levels of water vapour in the air. However, relative humidity should remain consistently between 40% and 60%.

Other things to consider when growing in winter

Temperature and humidity are the main issues that winter-time growers will have to deal with. Lighting is usually not an issue as plants are typically grown under HID lights.

Having said that, some hobby growers might still be eager to utilise as much natural sunlight as possible, such as growing on a windowsill. The problem with this is that light intensity or simply the amount of sunlight hours may be insufficient for growth. Each area will vary in its wintertime habits, and each grower should make choices accordingly.

Some clever growers will use extra lighting during winter only, to ensure that their plants have enough light to grow. While plants will usually not achieve the yields and qualities achieved in more favourable times of the year, there are plenty of smart hobby gardeners out there that will ensure their supply remains steady even in the harshest times of the year by following this principle.

Greenhouse growers are similarly affected by the reduction in daylight hours during winter, and unlike those growing on their windowsill at home, additional lighting may attract unwanted attention.

However, some adventurous greenhouse growers will add the supplementary lighting and then make sure that the greenhouse is covered so that light does not escape when it is dark outside. Thick, heavy blackout curtains or Mylar sheeting can do an excellent job here. Then, all that remains is to heat the greenhouse sufficiently and provide adequate airflow, and growing throughout the winter should become possible.

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Consider growing winter-appropriate strains

Every grower understands the temptation of growing their favourite strains throughout the winter, even if those strains aren’t really appropriate for winter growing. If you can let go of that temptation and choose winter-appropriate strains, you might be able to avoid some of the difficulties in growing over a snowy winter.

Let’s look at autoflowering strains as an example. In as little as 8 weeks from germination of the seed, you can have a ready-to-harvest cannabis plant. This means that a grower can avoid growing throughout the harshest part of the winter and maximize their growing opportunity.

Any strain that contains ruderalis genes is also more likely to make it through a winter. Ruderalis is tougher and hardier than more common strains. It also isn’t photoperiod dependent, meaning it will flower when it’s ready rather than as a response to a change in light hours. It can bloom within 30 days of planting.

Growing in winter might mean doing some additional planning in advance to prevent the demise of your plants. But that doesn’t make it impossible. After a couple of seasons growing weed in a snowy winter, it should start to feel like second nature.

Laws and regulations regarding cannabis cultivation differ from country to country. Sensi Seeds therefore strongly advises you to check your local laws and regulations. Do not act in conflict with the law.

​How to Speed Up Seed Germination During Winter and Spring

If you live in a colder part of the nation and are an avid gardener, you’re probably champing at the bit to get some seeds in the ground. If you have a greenhouse, that might only be a few months away. If you’re a gardener in a colder state like Colorado, you’re going to have longer to wait. And no matter how long your growing season is, you’re likely to want to get to harvest faster once you plant your seeds. Which leads to a topic that often comes up here at our nursery supply company: how to speed up seed germination.

It’s a question that home gardeners and nursery suppliers have been asking for a very long time. While genetic engineering can help a plant grow faster, there are some aspects of speeding up seed germination that you can control. Let’s take a look at ways that you can get those seed popping faster.

Soak Them In Water

There’s not much easier advice than this! All you have to do is pre-soak the seeds in hot tap water for 24 hours. The water penetrates the seed coat and allows the insides of the plant to break from the seed more easily. Usually this occurs naturally in the soil, but it can take a much longer time.

The only thing you have to be careful of is letting the seeds soak for too long. Any longer than 24 hours and they could start to rot even after you put them in soil.

Scarification

Scarification is another physical means of speeding up seed germination. The purpose of a seed is to protect what’s inside and then provide initial nutrition to the plant. Because of this, the seed coat is quite hard and fairly good at protecting its interior. Scarring the seeds will remove a bit of this seed coat in order to let water in, which starts the germination process.

There are a couple of ways that you can scar a seed before putting in a ground. If you only have a few that you’re planting, you can take a knife and knick each seed, or scrape each with a bit of sandpaper. But that can get quite tedious if you’re planting hundreds of seeds, so you can speed up the process by shaking them in a jar with a piece of sandpaper.

Seed Stratification

Seed stratification is the process of tricking a seed into germination earlier than it would when it’s out in the wild. Stratification is often used for wildflowers that have a very hard outer coat on their seeds. This coat prevents the seeds from opening too early in the wild if there’s a particularly warm February day.

Seed stratification is necessary for plants that are expecting to overwinter in the ground. But if you get your seeds in the mail in March, you don’t want to have to wait another entire year before you can enjoy them. Seed stratification involves putting seeds in a moist, soil-filled bag for a time, usually 10 days to three months. This “tells” the seeds that they are cold, and that they can go ahead and wake up and start germinating. This process is especially good for our nursery customers who need full plants to sell to customers by April.

If you get your seeds in the fall and can actually make use of the natural cold outside, you can overwinter them in your garden. The problem with this is recovering the seeds later, because locating them can be difficult. The best way to find this is the put them in pots and bury the pots themselves, then dig them up and transfer to them wherever you want them when they start to sprout.

Keep Them Warm

No matter the kind of plants you are using, there’s one thing that most of just love: warmth. Keeping seeds warm tells them that the summer has arrived. Of course, that’s the purpose of most greenhouses. If you don’t have a greenhouse, keep the seeds in a south-facing window. You can even use something like a seedling heating mat that warms the seeds in their pots.

Don’t Forget to Harden Them Off

Plants that are started indoor have it pretty easy. After all, you soaked the seeds and scarred them so that the plant itself could emerge. Then you told them that winter was over and warmed them up considerably!

Since they didn’t have to work hard in order to get out of the seeds, seedlings haven’t been hardened by the world yet. They aren’t used to being cold or being whipped around by the wind, so seedlings that have been raised indoors are more likely to die than those that have been grown directly in the garden, even if they look identical.

Hardening plants is easy. Just take them outside in Spring for a couple of hours each day, then a bit longer each day after that. Eventually the wind will “harden” them to the wind and cold, at which point you’ll be able to plant them in the ground. Just don’t forget about them and leave them out overnight during their first day, or all of the work you did up above will be for nothing!

Then Come Back For Your Gardening Tool!

Of course, seed germination is on the first step to a healthy plant. Once your plants are growing in the garden, you’ll need to take care of them with the best garden hand tool around. Find them right here, and happy planting!