Every outdoor cannabis grower relies on accurate climate data and weather forecasts to plan a crop from seed to harvest. This coming growing season, ganja farmers in the Netherlands and surrounding countries will rise to the challenges of cultivation in an oceanic climate. We have created this grow calendar as a roadmap specifically for the Northern European cannabis road warriors.
• Day length: 9.05 – 10.47 hours • Average temperature: 2.5 °C
February is far too cold and dark to rush outside and start sowing seeds in the dirt. Temperatures will be close to freezing by day, and may dip below zero overnight. The online climate charts will tell you to expect approximately 10 hours of sunlight this month. In reality, you won’t see much sunshine through overcast skies. There is also still a significant risk of snowfall. This is the month to research cannabis seed genetics, weather forecasts, and to gather supplies. Most of the essentials like soil and fertilisers can be found online. But it may take a couple of weeks before all the deliveries arrive.
• Day length: 10.51 – 12.52 hours • Average temperature: 4.7 °C
Still too cold outside. Probably pretty cloudy most days as well. But you can kick-start the grow like a pro indoors. By now, you should be in possession of all the outdoor cultivation essentials. With a minimal investment, you can acquire a basic CFL lamp and reflector to start seedlings indoors. Whether you are growing from seed or using clones from a trusted source, it helps to get plants rooted before you put them outside
• Day length: 12.56 – 14.48 hours • Average temperature: 8.2 °C
By the middle of the month as daily sunlight increases to about 14 hours, you can begin to make a move outside with plants in 10–20l pots. Temperatures will be in the low teens at best, so only the strong will survive outside this early. Hardy autoflowering strains are definitely the best option. Blue Cheese Automatic by RQS or Early Skunk by Sweet Seeds are rapid bloomers and cold-weather-hardened.
Although tough photoperiod hybrids like Durban Poison by Sensi Seeds or White Critical Express by Kalashnikov Seeds will receive sufficient sunlight for vigorous vegetative growth, late-blooming sativas are to be avoided as the growing season is just not long enough in northern latitudes. Old-school Holland’s Hope and Early Girl will perform well in a greenhouse. But if you want high-grade weed, you need to be a little more patient.
• Day length: 14.52 – 16.20 hours • Average temperature: 12.3 °C
Purists can germinate seeds and start them on a sunny windowsill. As daily sunlight reaches 15 hours and the temperatures stay consistently in the low-mid-teens, it’s finally the right time for most to grow outdoors. Fast-flowering strains are still the best choice. Classic Skunk and Northern Lights by Zamnesia Seeds are solid choices. Alternatively, you can start a dank super auto like Royal Gorilla Automatic by RQS or Devil Cream Auto by Sweet Seeds.
However, if you got started inside, May is the month to harden off and make a move. Start by potting up to large 10–20l final containers. Use your artificial light to supplement the hours of natural sunlight. Using pots allows you to move plants in and out. By the end of the month, they are ready to grow outside permanently.
• Day length: 16.22 – 16.38 hours • Average temperature: 15.2 °C
With a little luck, temperatures will be in the high teens, and by the summer solstice on the 21st, daily sunlight will peak at 16 hours and 38 minutes. Autos germinated in March/April will be ready for harvest this month. Provided they have been sheltered from rain, the buds will be of respectable quality and a decent yield can be expected. Photoperiod strains will vegetate comfortably and still have enough time to grow to large sizes and yield heavily.
• Day length: 16.37 – 15.29 hours • Average temperature: 16.9 °C
Sun-flowered autos started in May will be ready for the chop this month. You could potentially be harvesting your second crop if you get your timing right and selected the right genetics. Most photoperiod strains will still be in vegetative growth and it could be time to do some pruning and training if plants are beginning to turn into trees. Temperatures in the low 20s and 15+ hours of sunlight are great conditions for growing cannabis.
• Day length: 15.26 – 13.37 hours • Average temperature: 16.7 °C
Photoperiod strains will begin slowly transitioning to the bloom phase this month. And if you got a late start with your autos, don’t fret; you still have time to finish flowering this month. By the end of the month, you are back down to about 13.5 hours of sunlight per day. This is not a perfect 12-12 light-dark cycle and is the reason why photoperiod strains take far longer to bloom outdoors. If you have a greenhouse, you can cover it over with light-proof sheeting to reduce the hours of natural light and speed up flowering.
• Day length: 13.34 – 11.39 hours • Average temperature: 14.2 °C
If you haven’t already, now is a great time to build a simple shelter for cannabis plants in mid-late bloom. Heavy rainfall is not uncommon in September. Daily sunlight will decrease from 13 hours and 34 minutes to 11 hours and 39 minutes in 30 days. Be on the lookout for threats to the buds. High humidity and decreasing temperatures to the low teens are a recipe for bud rot. Better to harvest a little early than to lose the crop. Photoperiod plants should be harvested towards the end of the month. September is potentially a third auto harvest month. Autos sprouted in June/July will certainly be ready.
• Day length: 11.35 – 9.38 hours • Average temperature: 10 °C
You had better be close to the finish line to be still growing this late in the year. Temperatures will be 10°C at best and sunlight is fading fast. By Halloween, daily sunlight hours will be back down to single digits. Get trimming and harvest as soon as you can. Winter is coming! November, December, and January are months for hibernating with a fat stash.
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