How Much Sunlight Is Needed for Marijuana Plants

How Much Sunlight Is Needed for Marijuana Plants?


How Much Sunlight Is Needed for Marijuana Plants?

When it comes to growing marijuana, sunlight is an essential element. Without sunlight, photosynthesis cannot occur, and plants will end up dying. While growing cannabis plants outside is a natural way to produce a healthy crop with a high yield, controlling the amount of light your plants are exposed to is not always easy. With this guide, you will better understand how much sunlight cannabis plants need and how you can control the amount of light they are exposed to during each phase of growth.

Understanding the Importance of Sunlight

While marijuana plants are highly durable and able to thrive under many conditions, this does not mean they can grow without light. Although the soil you use and how much water the plants receive is highly essential, sunlight is most critical and makes the most significant difference in the growth and final yield of cannabis plants.

A marijuana plant cannot produce stems and leaves without adequate sunlight. The leaves are the part of the plant that help it take in critical energy from the sun. If sunlight is lacking, the plants will grow “leggy” and will not produce many leaves because they are looking for an energy source.

Cannabis plants use a process called photosynthesis to create food. Without this vital process, plants cannot thrive. Cannabis plants, like all other plants, use their leaves to trap energy from the sun. Once this energy is absorbed, the plant goes to work on converting water and carbon dioxide into glucose, which is the food source for all the cells in the plant. Glucose is a critical element of producing the healthiest cannabis plants because it plays a role in the cells’ manufacturing cellulose and starches.

Placement Is Critical for Sun Exposure

It takes considerable thought to determine the best place to plant your cannabis. Without the right arrangement, the plants will not receive the full sun they need during each stage of development.

Cannabis plants need a lot of sun exposure, so it is essential to plant them in a sunny location where they can receive up to twelve or more hours of full sun each day. Those living in the Northern hemisphere are going to want to plant their cannabis at the south end of their property. If you live in the Southern hemisphere, plant them at the northern end.

The area you plant in must be free of objects and other plants that will hinder sunlight absorption. It is wise to check the area throughout the day to see if there are any periods where shade could become a problem. Remember, the more sun your plants receive, the higher the yield, so it is worth investing time in the process of finding the ideal planting location.

For some reason, perhaps because of legal concerns, many growers attempt to hide their crops by growing them in wooded locations. If you understand anything about the science behind photosynthesis and plant development, it is clear to see that this is problematic and will result in stunted growth with much less yield.

What Do You Need to Know About Light Periods?

Each stage of cannabis plant development needs a specific amount of light. The period for light exposure is essential because it will affect yield and quality. There are two main stages of growth for marijuana plants, and each one has its light requirements, depending on the strain.

The vegetative stage requires approximately 18-24 hours of light. With sunlight limitations, this is impossible when growing cannabis outdoors. You can supplement with outdoor growing lights during the night.

The vegetative stage begins after the seeds sprout. When growing outdoors, it is essential to plant early in the spring for maximum sunlight exposure for as long as possible during the day. Planting in the spring ensures the plants have plenty of time to grow leaves before entering the flowering stage.

The flowering stage requires at least twelve hours of complete darkness. Your plants must not be exposed to any light source during those twelve hours, including streetlamps, solar-powered lights, or decorative lighting. Make sure to plant cannabis in an area that will be exposed to none of these, for the best results.

Photoperiod Dependent Vs. Auto-Flowering

When it comes to marijuana and sunlight exposure, there are two main types of plants you can purchase. Photoperiod dependent strains are the most common, and they entirely rely on sun exposure to determine their stage of growth.

Auto-flowering cannabis strains are hardy and can go through each stage of development, regardless of how much sunlight they are being exposed to throughout growth. This type of seed is not readily available and often needs to be purchased from specialty cannabis seed suppliers like Weed Seeds Canada.

Understanding the Outdoor Growing Seasons

While growing cannabis outdoors is more challenging, it is worth the effort. It is wise to research the strains and seasons to determine the best time to plant. Consider the following when deciding what season to introduce your cannabis crops to the great outdoors.


If you are planting photoperiod cannabis seeds, spring is the ideal season to plant. The best time to put your plants outside is after the spring equinox and before April ends. During this time of the year, the days are long and warm enough for most strains of cannabis to thrive.

Cannabis that gets planted in the springtime are going to produce large plants with a high yield, which is what every marijuana grower is after. It is important to note that most strains of auto-flowers can also be planted during this period.


While most southern growers are likely on their second crop during the summer, northerners may just be getting started because temperatures are finally rising to manageable numbers. It is critical plants are hearty before the summer solstice because environmental changes begin around this time and can affect the final yield of the plants. After the summer solstice, you will notice photoperiod strains will grow more compact and are likely to bloom sooner, while auto-flowering plants remain squat. It is wise to keep this in mind when timing your planting season. Fast flowering strains may do better than photoperiod strains if planting in the summer.


When October rolls around, marijuana growers start to think about harvesting when growing outdoors. The days become shorter and shorter, with some parts of the country seeing fewer than ten hours of sunlight in a day. With colder temperatures just over the horizon, it is vital plants are harvested at the right time.

The autumn months often bring in a lot of rain. When the rain becomes coupled with cooler temperatures, it is possible to see your colas start to mold, and this can quickly destroy a crop of cannabis.


Winter is mentioned here, only for keeping the seasons in order. If you are an outdoor cannabis grower, you must harvest your plants no later than Halloween to avoid crop loss. When daytime temperatures start falling consistently below 53° F, the plants will not survive.

Colder temperatures cause cannabis plants to slow down their metabolic processes. With decreased metabolism comes a decrease in enzyme production. Too much cold and not enough light renders the root system of a cannabis plant entirely useless.

Get a Head Start

No matter when you plan to plant your cannabis crops, getting them started indoors is a wise move. When cannabis first sprouts, its leaves are very tender and vulnerable. Once your seeds sprout, expose them to an indoor growing light for eighteen hours a day, with a six-hour darkness period. This is the optimum ratio for healthy vegetative growth.

Keeping your cannabis plants growing indoors for a couple of weeks will allow them to develop a healthy root system. Plants that have fully rooted are going to be more hearty and able to survive outdoors in the elements.

You do not need a lot of equipment to get your seedlings started. Even a cool 200-watt CFL bulb will be sufficient for this stage of development. Planting seeds in the ground is not wise because you may find the seeds sprout, only to dry up and die because they are not ready to be exposed to the elements in this stage of vulnerability.

Bottom Line

Growing marijuana is a fun process that takes a lot of work and offers even more rewards. There is nothing more pleasurable than enjoying your first cannabis crop. To ensure your plants are healthy and the yield is high, sunlight exposure must be carefully monitored and maintained.

Planting in the spring and in an area that offers the maximum amount of sunlight exposure each day is essential. Your cannabis plants are going to need plenty of sunlight to help with photosynthesis and the conversion of water and carbon dioxide to plant food.

Follow the above tips to ensure your cannabis plants are getting all the beneficial sunlight they need at all stages of development. Sunshine is especially critical during the vegetative stage when stem and leaf production is occurring. If you make a concerted effort to keep your plants exposed to the proper level of sunlight, harvest time will be much more bountiful. Check out Weed Seeds Canada to select your seeds!

What Do You Need to Know About Light Periods?