Growing Cannabis Outside in Canada



With the spring equinox this week, many are asking when to start plants? When to plant outside? And how long until harvest?

First rule of outdoor gardening in most of Canada:


Why? We get winter. Spring overnights can be cold. Cannabis growth stunts below 15C, and some strains will stress above 30C.  Ideal temperature for cannabis is 18C at night and no warmer than 28C during the day.

I live in Alberta near the Rocky Mountains, my season is short and winters are real. The spring equinox is this week, and the sun is strong! That said I still have 2 feet of snow melting in my backyard! Spring comes late and, winter comes early here.

Cannabis (sativa and indica) is a photoperiod plant (I’ll leave auto-flowering ruderalis for a different post), meaning cannabis is triggered to grow with long summer days, and flower with the reduced sunlight hours of fall. For comparison: most indoor growers maintain a vegetative state using a 18:6 light schedule, and flowering is induced by using 12:12 schedule.

So… for a successful outdoor grow, you need to understand how much light your specific location gets & when.

A good tool to establish this for your location is this tool:

The equinox’s are important, as this is when the sun is 12:12 (equal day and night). The spring days get longer until the summer solstice on June 18 2019 – the longest day of the year. From there the day’s get progressively shorter until the fall equinox on Sept 21 2019 and we’re back to 12:12. Here’s the catch, depending on your latitude, my northern spring is short, I get long days in summer, then a super short fall. By end of October, I’ve dropped to only 9’ish hrs of daylight and early winter has set in. Some Canadians enjoy a milder fall season and can finish flowering outside, I simply cannot. Winter comes too quickly.

So… Basically I have basically 2 choices:

– Finish plants in a greenhouse OR bring them inside and put under 12:12 lights.


– Light deprive your outside plants a month or so early so they finish early.

Lets talk light deprivation – The dark period. Although the natural environment provides natural moon light, additional light can cause problems. In an indoor grow, light leaks during the dark period can cause stress reactions like undesired hermaphrodites (they will seed your grow).  Pick an area outside that avoids additional lighting that extends or interrupts the natural dark period. This includes streetlights, backyard patio lights, or motion triggered lights. To induce 12:12 for flowering early, your crop needs to be covered daily to make “darkness come early”, and then uncover plants once natural dark arrives. This continues until either harvest, or the fall equinox arrives.

Here is a general outdoor grow schedule:

March – Order seeds, or take clones from a mother plant (known female).

April – Start seeds indoors/clones should now be rooted. Grow seedlings under a grow light (if using LED I prefer a full spectrum with blue enhanced).  Some use a window box that gets good sun for most of the day. Dont over water! Weak lighting will produce leggy starts as seedlings reach for light. Also adding a fan to gently blow on seedlings helps strengthen them.

May – Start hardening off seedlings to the natural sun with increasing daily exposure, bring them inside at night as it’s still to cold overnight (unless you have a greenhouse).

June – Plant outside. Ideally when nighttime temps stay above 15C

July – Watch your ladies grow! Consider toping or Low Stress Training to help manage height.  Watch for pests! Also watch for Males!

Male  Cannabis Pre-Flower

Males often mature faster than females, and will pollinate your entire grow, and on a windy day – your neighbours grow! Unlike females that produce bud, males produce ball like flowers that spray pollen so it can pollenate those buds! The cover pic on this post is a female in early flower.

Dispose of males! Spray them with water to avoid any flying pollen, then place a bag over them and pull them. Pollinated weed becomes seedy weed, and seedy weed is not good weed.

August – Considered the last month of summer, it’s time to induce flowering by starting daily light deprivation. This must be done daily until Sept 21. If left to grow naturally, you will start to notice some stretch between nodes and as the month progresses, and then pre-flowers will start as September gets closer. Note the day you see pre-flowers. Late late blooming males should also have shown themselves.

September – Fall equinox is Sept 21, 2019 (12:12) and flowers should be naturally developing. Move plants inside if necessary on cold nights.  If you light deprived your plants, depending on strain they should be ready to harvest about 8 weeks after they started to flower, this means an end of September harvest! Cut them when ready and cure your harvest.

October – Harvest your outdoor natural plants that have finished, cure your harvest. If in a location that lets them finish fully outside, you will probably witness some fantastic fall colours on your ladies.

Happy growing!


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