The seasons have changed. So have the temperatures with them. Are you seeing slower growth than previously? How much does the cold temperature affect your growth? Cannabis winter growing is an entirely different, but achievable discipline.
Many factors play a part in ensuring your plants stay in optimum health throughout the growth cycle. Taking steps to help guarantee that your plants perform at their best at every stage and hour of the growth cycle will reward you with the crop you have been dreaming of.
During the summer months outdoors, where plants are growing naturally with the sunlight and other essential elements, the temperatures during the day and night stay within a range that keeps the plant’s vitality at an optimum. This means that it is not being put into stressful situations that inhibit its growŧh.
Have you ever seen a cannabis bush the size of a house growing outdoors along the west coast of America? These plants grow so large because they are in such ideal conditions, leading to exponential growth and bumper yields.
So what are these conditions that plants require to stay on point day by day through the growing cycle?
Why Temperature Matters when Growing Weed
As covered before on the Seedsman blog, temperature has a fundamental role in ensuring the plant’s natural and vital functions can perform.
When we are indoor growing in a shed or loft space, and it’s the opposite time of the year to when cannabis plants naturally want to grow, it is your job as the gardener to deliver the planŧ’s needs. But this doesn’t just mean when the lights are on; we need to think about the temperature every hour of the plant’s life.
During the flowering cycle, which lasts 8 to 10 weeks in most hybrid cultivars, any slacking in keeping control of the correct temperature will lead to a drop in yield. You have to look at every week of a plant’s life as a decade. Considering temperature can have an impact on the plant’s ability to uptake nutrients and photosynthesis, you only have to imagine what effect this has when you think about depriving yourself of the proper heat and nutrients you need to thrive for ten years – you wouldn’t want to if you had the choice.
While the air temperature of your grows space, whether it be a room or tent, is a vital factor to keep within a set range, you also want to take steps to make sure that your root systems are also being warmed sufficiently – or even – not being overheated if you are adding in supplemental heat via a fan heater.
A plant’s root zone works best when it is at a temperature range between 18C and 20C. This doesn’t seem like a huge range to operate in, but it is perfectly possible to maintain this temperature range with a few affordable tools. Above ground, the plant controls the temperature of its exposed parts via transpiration within reason.
How to Accurately Monitor the Temperature in a Grow Room
If you think that your growth is slower than it should be since the temperatures have dropped, but when the lights are on, everything seems just fine it may be that when the lights are off, the plant is getting too cold. To help you identify this, you can buy cheap data loggers online that connect to your phone via Bluetooth.
These data loggers work by tracking the temperature (and usually the humidity) and provide you with a graph that indicates the temperature when it is taken. You will probably discover that there is a quick decline in temperature when the lights go off, and the plant is sitting at 12 degrees for four or more hours until the lights come back on, and that it still ŧakes 45 minutes to get up to temperature. This is just an example, but one that demonstrates that the plant is going into hibernation and taking a lot longer to wake up when the lights come on, eating into your crucial and already limited photosynthesis time!
How To Remedy Cannabis Grow Room Temperature Fluctuations?
As briefly touched upon earlier, heaters are an excellent way to increase the temperature of a grow space. There are even specific ones for greenhouses and developing spaces with built-in thermostats. Do not worry if you can’t get one with a built-in thermostat, though, because you can buy specific plugin thermostats to turn the heater of your choice on or off when the temperature drops below the set temperature (ideally no lower than 18C) and an upper temperature of perhaps 21C.
A rule has been observed growing many specific fruit and food crops indoors or greenhouses that if you can keep your day and night temperatures within a 6C range, you will have success (providing your feeding schedule is correct).
Nighttime temperatures are considered to be 4C lower than desired daytime temperatures, which are deemed to be 24-27C, so if you have a daytime temperature of 25C, you might like to aim for 21C as your stable nighttime temperature. The lower you go in this relationship, the slower growth you will see. Feel free to experiment from strain to strain as not all landraces evolved and were protected in the same part of the world, and most strains are hybrids now.
Different Heater Options for Cold Weather
In a small space such as an 80cm grow tent or cupboard, an oil radiator as little as 450watts can provide enough heat. But this will depend if you are indoors or outdoors or in a loft with or without insulation. If your data logger goes below 11C, then you probably want to get one that is 750watts or more.
The classic fan heater is good at quickly warming up an area and spreading the heat out over a more expansive space. With the fan heaters, you can get away with not having them on constantly, which can be required more for the oil radiators. If you don’t have a thermostat, you can put the heater on a timer once every hour to maintain the desired temperature. But consider, it will probably be something you have to spend some time configuring, and this may change over the two months of the flowering period as outdoor temperatures vary. With this in mind, you need to keep your eye on it and not get sloppy – if your desired outcome is to regulate the temperature.
Bar or tube heaters are similar to oil radiators in the way they give off heat. They are ambient and can aid in raising the temperature slightly – but if you are in very low temperatures, you may want to think about a fan heater. Remember, heat rises, so it is good to have your heat low down and with enough room in front to distribute the heat evenly.
If you are struggling to keep the bottom of the rootzone warm, then here’s a suggestion that I have been utilising for the past decade. Electric blankets. They are waterproof as they are made to be machine washable and suitable for beds where accidents may occur. Putting one of these underneath the waterproof tray or sheet in your tent/room will act as a giant heat mat like when you’re taking and trying to root cuttings.
My favourite way to regulate temperature is a thermostat, however. There are a number of these on the market depending on what country you are in or access you have to hydroponic shops, but universal options such as an Ink Bird can provide the essential control that you need. They even have an alarm to alert you if the temperature does go outside the set range, and these can be sent to you in real-time via wifi if you pay for that version.
Things to Remember When Adding More Heat
It would be a brutal thing to come see your hard work has been fried by the fan heater you installed the night before. Make sure you sit with your plants for a while when you have added something like this in. Take the time to look at the direction of the heat and if it is too focused on some area of the canopy or side of one pot that could get really hot and fry the roots and microbial life if exposed to direct heat for a long time.
When you start adding heat, you can change the humidity, another vital factor in ensuring the plant’s transpiration rate is within the optimum range. This is why I feel a data logger is such an essential bit of kit and strongly recommend you get one if you want to be in charge of your garden.
Watch the moisture content of your growing medium. If the soil or rockwool/coco gets too dry too quickly, this could lead to a salt build-up and mess with your EC and pH level. If you find your pots are drying out too fast and you have to hand-water more often, have some pH-ready water to use that is low or no EC just to keep the correct moisture level without over adding more nutrients in. You may need to add or remove a dehumidifier if you’re seeing a lot of fluctuation with humidity levels.
It is essential to practice this throughout the vegetative and flowering stages, not just the flowering stage. If you don’t have the mass on your plant before you flip it into flowering, it will not have the architecture needed to pack on the weight you desire and may never reach its full quality potential.
Always keep in mind that your grow lights can and will influence the temperature, especially if you’re in a grow tent as opposed to a room. Led lights are perhaps the easiest to use as they don’t give off a lot of heat.
Strains that Do Well in Cold Climates
If you’re looking to start your germination before Christmas and get a grow started during the winter months, perhaps you should opt for a cannabis strain that’s better equipped for the winter growing season.
Some people are against using autoflowering strains this time of year but that’s not entirely accurate. Due to their genetics, Ruderalis plants are quite resistant to harsh temperatures and fluctuations. They’re not as dependent on the photoperiod as other cannabis plants. So don’t be afraid to try an auto this winter!
White Widow Auto
White Widow Auto takes the legendary White Widow strain a stage further so that growers no longer need to worry about reducing photoperiods in order to stimulate the onset of the flowering cycle. The White Widow marijuana strain has long been one of the most popular of the Seedsman strains, and with good reason. It is famous for its fast and hard-hitting feeling which evolves into a very pleasant, relaxing effect.
The introduction of ruderalis genetics allows harvesting of trichome-covered frosty buds in only 11 weeks from germination from vigorous, quite short-statured plants that enable discreet crops that’ll suit a small grow space. Yields are pretty impressive; up to 125 gr per plant!
One of the most consistently popular strains in the United States, Bubba Kush has gained recognition for its sedating effects. A truly dominant indica in almost every way, Bubba Kush is somewhat squat in stature but offers large leaves and a unique, packed bud structure whose shades and tones are rainbow-like in their hue range. The parents of this new strain from Seedsman are both Bubba Kush varieties from the mid-1990s. Reports suggest that the strain itself didn’t emerge until 1996, which means that with Seedsman’s Bubba Kush, you will be getting the truest version of the variety – just how its creator intended it to be.
Suitable for all grow media and a great cannabis seed for first-time growers, Bubba Kush is especially ideal for those working in smaller cultivation spaces.
Northern Lights Auto
Northern Lights Auto was created by crossing Northern Lights with a ruderalis strain to add auto-flowering properties. It is a robust and resistant indica-dominant hybrid producing high levels of THC and good yields. Like most auto strains, it grows well in all growing environments. Indoor, it grows to 80 – 110 cm. tall with its flowering life cycle completed in 55 – 60 days, following a 2 – 4 week vegetative growth period, and producing about 500 gr/m2 when given 18/20 hours of light per 24.
Cannabis cultivation is straightforward, preferring moderate levels of slow-release fertilizer. It has good resistance to fungus, plant diseases, mildew, bud rot, and pests. Towards the end of its life a range of green, blue and purple shades will both surprise and delight cannabis growers.