Transitioning Cannabis Outdoors

This week (May 17-21, 2020) should be a great week to move your cannabis plants under the sun. It can be nerve wracking to do this and frequently you will end up with burnt plants if you transition too quickly. However, the weather right now is nearly ideal to get this done.

This week’s forecast includes cool temperatures and overcast skies. This means that the sky will provide a natural shade that should greatly reduce the chances of light-burn to your plants. Light-burns occur when a combination of heat and light intensity actually damages the plants. Instead of blistering as human skin would, chlorosis (yellowing) is quickly followed by necrosis (death) of sensitive plant tissues.

The cannabis plants will display varying levels of sensitivity that are driven by a couple primary factors; indoor light intensity, and genetics. Some varieties of cannabis can tolerate a lot of light stress normally. I could explain why, but I’d mostly be guessing. What we can talk more about is the type of light you used indoors to start the plant.

If you use a shop-light or some sort of low intensity light, your plants will be more likely to burn given that full sun-light (up to 2000 PPFD) is vastly more intense than flourescents (up to 400 PPFD). On the other hand, if your plants enjoyed a top of the line LED (up to 1700 PPFD) that you have dialed up to full intensity, then the transition to natural sunlight will be much quicker.

Making the transition

A shade tree can be used if the sun is bright and it is warm outside. The indirect light a plant gets will still be stronger than your weaker indoor lights. Position your cannabis so that it will receive sun light after about 4-5 pm (west side of the tree). On the third day, move them slightly westward so that they get full sun starting at 3pm. Increase the amount of full sun each day until full dawn-dusk sunlight is achieved. This is a great method if you can’t babysit them all day because you should only have to adjust once per day.

Alternately, a shade cloth can also be employed and you will find that 80% shade cloths are most common. 80% light blocking will surely prevent the plant from becoming burned and you can use that cloth much like the shade tree above.

You may also be able to use the north side of a building, privacy fence, etc. to provide the needed shade. Move the plants into the sun for an hour, then back to the shade for the rest of the day. Increase exposure to full sun by an hour or two each day until full sun is achieved. It will require more babysitting, but is very doable. Both of these methods will take a week for the most sensitive plants.

Watching for light-burn

The earliest signs of light stress will be drooping leaves; imagine that the sun is melting the plant. Soon, leaf tips and edges may begin to curl, which usually means some damage will become apparent in the next day or two. If you see yellowing already then the plant is in distress. If you notice any of these signs, move the plants to shade immediately and wait for 24 hours to assess any damage that may have occurred.

Avoid letting your soil dry as well. Cannabis, like most plants, also uses transpiration (of water vapor and gasses) to control leaf surface temperature. Ensuring adequate water will help with this transition.

When at temperatures over 80 degrees, light stress can show itself very quickly in sensitive plants. Temperatures below 55 seem to cause the plant to have trouble adjusting to environmental changes (like light), and is likely due to a slowed metabolism.

All that being said, this week is the week! Cooler temperatures coupled with overcast skies that transition to partly cloudy by the end of the week makes for the perfect conditions to transition your cannabis to its new outdoor home.

What are you waiting for?

Happy Harvests!
– The Lit Farmer –