Solstice and Light: Outdoor Grow Tips

Heady Vermont Staff 21 Jun 2020

Learn about what the earth’s rotation and solstice and light mean for your outdoor cannabis grow.

The Earth takes approximately 365.26 days, or one year, to complete one orbit around the sun. It spins at an axis of 23.5 degrees relative to the sun. Due to this tilt, the two hemispheres will, depending on the time of year, have either a longer-than-average or shorter-than-average exposure to the sun per day, always waxing or waning in one direction or the other. This difference in sunlight results in the seasons.

(Wikipedia) Seasons in the northern hemisphere.

This matters in outdoor cannabis gardens is because cannabis uses a process known as photoperiodism to determine when to flower. Specifically, flowering in cannabis is triggered by long daily dark periods. This makes cannabis a short-day (or long-night) plant. Artificially lit gardens take advantage of this by denying the plants long dark periods to keep them growing until they have reached the desired size. Limiting the dark period to six hours or less is a common method, although any schedule that avoids a long continuous dark period should prevent flowering.

There are many, many more variables and things to learn about outdoor cultivation, but here we are focusing mainly on outdoor light and the earth’s calendar.

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Important dates

The short winter days get longer until day and night are equal at the vernal equinox.The Spring Equinox reminds us that it’s time to kick off the outdoor growing season and start germinating our seeds.

The summer solstice, also known as midsummer, is the longest day of the year. As the sun gets to its highest point in the sky, your cannabis wants to play outside too. Make sure all of your plants are outdoors by the Summer Solstice. The months around the summer solstice are the only months that do not have long enough nights to trigger flowering in cannabis.

Want more on outdoor cultivation? Check out Joe Veldon’s writeup on Sun Grown Cannabis.

More cultivation tips on our Cannacurious page!

Fall is a time of transition. The days continue to get shorter and the nights longer until they are again the same length at the autumnal equinox. The weather will start to turn and the sun will begin descending in the sky as your plants fatten up with gooey buds. Resist temptation and wait until around the Fall Equinox to start harvesting, but keep your loupe handy for inspections.

Everything should be cleaned up, dried, and curing well before the Winter Solstice. Now’s a good time to make your own homemade goodies with all that trim from the harvest. Kick back and relax, and enjoy the fruits of your labor!

(Leafly) Time frames on this graphic are ranges of time for the Northern Hemisphere – adjust them based on your specific region and local weather and climate. 

Germination Times and Plant Sizes

When you start growing your seeds depends partly on how big you want your plants to be for harvest. If you’re going for high yields, the earlier you grow your plants, the bigger they’ll be. On the other hand, smaller plants are more manageable and easier to top and prune. As the length of the days wanes and your plant enters into flowering, you will begin to get an idea of final size. Keep in mind that your plant will continue to grow during flowering, albeit slowed.

Homegrown Cannabis Co's Grandaddy Purple Seeds

Pay attention to the flowering times for the strains you are growing. Indicas generally mature more quickly than sativas. Think about how much time will be between when you started your plants, when you put them outside and when you’ll reach 12/12 at the fall equinox.

Moving Outdoors

cannabis plant, cannabis, nature, flower, growth, plant, green ...Whether starting from seeds or clones, many cultivators start growing their plants indoors to ensure the plants are not exposed to excessive weather conditions as they develop their initial root system. The plants are transitioned outdoors when the weather and photoperiods, or the times in which a plant is exposed to light, are ideal.

If germinating seeds or obtaining clones and growing them indoors first, you want them to get at least 6 inches – 1 foot in height before putting them outside, so they’re big and strong enough to handle the weather. If they’re a bit smaller or you started late, that’s okay! You’ll just have smaller plants.

There are a range of ideas on when is the best time to get your plants outside (at least, in colder zones), starting around Mother’s Day. Generally speaking, you want them in the ground by Summer Solstice.

Location, Temperature and Light

Cannabis loves sunshine! Your cannabis plants should receive as much direct sunlight as possible, at least five hours a day. If you’re planing in the ground or in large, heavy containers, think about where the sun will be later in the season as the sun gets lower in the sky and rises and sets more toward the south.

Excessive condensation, especially in the fall, is mold waiting to happen.

Temperatures should never exceed 86°F or drop below 54°F. Keep this in mind when choosing your spot. As fall approaches, you may need to cover your plants if you think it might get cold, but don’t forget to remove the cover in the morning so your sticky buds can get circulation! Excessive condensation, especially in the fall, is mold waiting to happen.

Look for a plot that gets direct sunlight early in the day, through midday if possible, and filtered sun later in the afternoon or evening. It is also ideal if you can find a place that offers a constant breeze (ie, circulation between the leaves and buds). This can alleviate problems associated with high summer temperatures as well. However, bear in mind that lots of wind increases water consumption. If you’re in a high-wind area, try to plant along a windbreak, of course keeping the seasonal light in mind.

Solstice and Flowering

Light schedules intended to induce growth simulate the light around the time of the summer solstice. Summer occurs in a hemisphere when it is tilted toward the sun, resulting in longer days, shorter nights, and generally warmer weather. It occurs near June 21 in the northern hemisphere and near December 21 in the southern hemisphere. As the light gradually reaches 12 hours of sun, and 12 of night, the plant begins to flower.

Practice makes perfect, so always keep a grow journal and make sure to record any mistakes and wins.

If flowering during these months is desired, outdoor plants could be covered with opaque sheeting to lengthen the dark period. This allows for flowering to start earlier than it would naturally.

Practice makes perfect, so always keep a grow journal and make sure to record any mistakes and wins along the way. Maintaining a record can help ensure you will have successful future harvests. Be sure to record everything – from watering schedules to nutrients to soil and pruning. Photos can be helpful for future reference as well.

Keeping the seasonal light in mind and using the tools at hand, many different possible outdoor gardening schedules and plans can be developed to best suit your needs and available resources. Have fun and soak up that midsummer sun!

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