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Sunlight Requierments for Cannabis Plants

Apr 1, 2020
Lighting Problems

Cannabis Plants and their Sunlight Requirements

Though many growers have great success with indoor gardens, natural sunlight provides the perfect light spectrum for marijuana plants. If you’re planning an outdoor cannabis garden, it’s important to understand why and how sunlight is one of the most crucial resources. In this guide, we’ll explain everything growers need to know to take advantage of the sun’s rays.

Sunlight Requirements for Photoperiod Cannabis Strains

A photoperiod cannabis strain is a regular short-day variety that thrives on equal amounts of light and darkness. Simply put, they need 12 hours of sunlight and 12 hours of night. Indoor cultivators use timers to set these schedules and those for other phases; for instance, the vegetative st          age requires an 18/6 lighting schedule.

Many variations exist, and some growers see the most success with a 24-hour lighting period. Cannabis plants can survive with as little as six hours of daily light. However, we’re in the business of making plants thrive, so we suggest starting your outdoor garden when the days are at their longest.

When growing marijuana outdoors, nature runs the show. By studying nature’s habits, though, it’s possible to learn where and when to grow quality cannabis naturally. After the vernal (spring) equinox, the days will gradually grow longer until June 21 or the summer solstice. From there, the days slowly get shorter. Long nights trigger the flowering phase in photoperiod cannabis. Without a switch to a 12/12 lighting cycle, the transition is much slower in outdoor gardens as natural light hours only decrease by a few minutes each week.

Sunlight Requirements for Autoflowering Cannabis Strains

Though all auto-flowering strains are a bit unique, they have one big thing in common; the clock starts ticking the minute the plants start to flower. Today, this might mean that your crop will be ready to harvest within eight to 12 weeks. Most auto-flowering varieties start to sprout between 25 and 35 days after germination.

Unlike photoperiod strains, which take their cues from the sun, auto-flowering strains don’t require long and uninterrupted periods of darkness to flower. Modern auto-flowering strains prefer longer days, but they’re more tolerant to weaker light and interruptions. Furthermore, ambient lighting won’t convince these plants to revert to the vegetative stage, as would be common in photoperiod strains. Auto-flowering plants are more versatile, and they’re biologically engineered to bloom by the fifth week.

A Guide to Outdoor Cannabis Growing Seasons

Everyone knows that the Earth orbits the sun. However, it’s not the space between these two bodies that bring the seasonal changes we all know. Our orbit is an elliptical one, so the distance between the Earth and the sun may vary depending on the time of year.

Earth’s axis tilts at about 23.5 degrees, causing the North Pole to tilt toward the sun during June, July, and August in the Northern Hemisphere. During this time of year, it’s winter in the Southern Hemisphere.

  • After the vernal equinox and before April’s end is the best time to plant photoperiod cannabis The days grow longer and outdoor temperatures are warm enough for most strains, from indicas such as Northern Lights to sativas such as Amnesia Haze. Plants will thrive, and they’ll have a longer natural vegetative phase. Most auto-flowering strains are viable options for a quick harvest. In certain parts of the world, such as Northern Europe, springtime isn’t the ideal time to grow cannabis. Snow, hail, and other extreme weather are quite common through March. Freezing temperatures and overcast days aren’t very conducive to outdoor cultivation efforts.
  • Summertime will allow Southern European growers to see their fully-grown photoperiod plants in full bloom. By the end of August, some strains will be positively full of those delicious, dank buds. However, if you’ve started with a skunky, resilient auto-flowering strain, you may be able to plant a second summertime crop.
  • In the fall, things get interesting. October is often referred to as “Croptober” by farmers in the United States. During September and October, most of the Northern Hemisphere’s growers are getting ready to harvest. Further north, daylight hours may be approaching the single digits. Rain may spoil colas, and if you’re living in a wet climate, consider harvesting a bit early.
  • During the winter, it’s not recommended to grow cannabis. In the Northern Hemisphere, Halloween is the cutoff point for cultivation.

No matter when or where you’re growing cannabis outdoors, it may help to get things started indoors. If you’re running an indoor grow op, or even a cool white compact fluorescent lamp, start your seedlings on an 18/6 vegetative light cycle. Once the plants have taken root, they’re more likely to stand up to the elements.

Precautions to take when Moving Seedlings Outdoors

When moving plants from an indoor grow room to an outdoor garden, it’s important to realize that they’ll take a bit of time to get used to their new environment and the change in lighting. In some cases, the lost vigor reduces or eliminates the advantages of starting seedlings indoors.

Strong sunlight contains more UV rays than the light emitted by indoor growing lamps, and it may be too harsh for plants that got their start under artificial lighting. Therefore, it’s not recommended to expose these plants to the sun all at once. Your plants should gradually acclimate to the sun; accomplish this by first placing them in the shade and giving them a bit more sunlight with each passing day.

Growing Large, Healthy Plants in Outdoor Lighting

Because of insufficient acclimatization, a plant immediately exposed to the sun may show signs of leaf burn or discoloration. Therefore, these plants would have to grow new leaves, which will inhibit the regrowth process.

While cannabis plants grow, phytohormones build up in the leaves and other tissues. When the days start to grow shorter in June, a plant’s flowering hormone levels gradually increase by the day. This happens at the expense of growth phytohormones, which slowly begin to decrease.

Starting Outdoor Crops at the Right Time

Flowering only happens when the plant’s phytohormone levels are conducive to the process. This is why outdoor growing periods are longer; it takes longer for plants to flower and become ready for harvest. Therefore, starting crops early may not always be the best option. Some strains are known for earliness, as they flower shortly after the natural photoperiod decreases.

How to Schedule Lighting for Maximum Yield: Things to Consider

Whether you’re growing cannabis in a grow room or an outdoor garden, knowing the right lighting schedule to follow will undoubtedly help maximize your yield. If you’re using a grow room with plenty of width and height, letting the plants remain in the vegetative phase on a 24/0 or 18/6 lighting schedule for eight weeks is the best bet.

With outdoor plants, things are a bit different. When planning an outdoor garden, keeping seedlings indoors on a 24/0 or 18/6 schedule until the risk of frost has passed is the safest option. Once the plants have been moved outside, simply let the sun do its thing. When the vegetative and flowering phases are over (which may take three to six months, depending on the strain), it will be time harvest those beautiful, big buds.

To Grow Great Cannabis, Let the Sun and Nature Do All the Work

Cannabis is a resilient and hardy plant that’s adapted to most of the world’s climates. From the dry and cool mountains in Afghanistan to the heat and humidity of Colombia, marijuana has, over thousands of years, built defenses against a range of harmful conditions.

However, it is still vulnerable to extreme conditions. Whether you’re dealing with harsh sunlight, heavy winds that break branches, or excessive rain and mold growth, outdoor cultivation presents challenges that are avoidable with proper planning.

Becoming well acquainted with your area’s climate and seasonal changes is one of the most crucial steps in growing top-quality outdoor cannabis. Before getting started, you’ll have to know the temperatures plants need to thrive, the seasonal photoperiod (the intensity and amount of sunlight available throughout the growing season), the right garden site, and proper timing of planting, tending, and harvesting.

Some cannabis strain’s genetics have adapted to certain climates and are more likely to thrive in certain conditions than in others. Therefore, cannabis cultivators pay close attention to the strains or cultivars they select. A bit of research goes a very long way in making a harvest more successful.

Bottom Line

Like other plants, cannabis grows best in a natural environment. Though it’s certainly possible to grow weed indoors and enjoy great success, many cultivators find it easier and less expensive to grow outdoors under the sun’s natural light.

There’s a lot to consider when growing cannabis outdoors. Apart from legal restrictions and nosy neighbors, you’ll have to deal with lighting requirements, seasonal changes, and many other factors. With the tips, tricks, and guidelines we’ve offered here, growers are more likely to end up with the bountiful crops they deserve.

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