How Much Light Does A Weed Seed Need


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How much sunlight does a weed plant need? What’s the right amount for your strain? Learn how to fulfill your crops’ sunlight demands for a bountiful yield. When cannabis seedlings have grown their second or third set of serrated leaves they are usually hardy enough to flourish in direct sunlight. Learn when that is and how to do that now. Cannabis seedlings require the right amount of water, light, and nutrients. Learn how to handle them to get the strongest marijuana plants.

How Much Sunlight Does A Weed Plant Need?

We know that all things flourish when placed in the sun. The question remains, how much sunlight does a weed plant need?

The first thought that comes to mind is as much sunlight as possible. While you aren’t exactly wrong, your list of “how-to” questions should include this one: how many hours of light does a weed plant need.

The main reason we grow marijuana is to see the fruits of our labor once it produces the most beautiful buds. Getting enough sunlight is one of the key sources it needs to do so. Being clued up about it can only be beneficial to you and your crops.

Below we’ll discuss this further and determine how much sunlight plants need so that you can enjoy the finer things in life. Knowing your cannabis crops are getting the right amount of sunlight, just the way they like it.

Why does weed need sunlight?

Given all the benefits the sun-grown cannabis receives from sunlight, growers can walk away with a bountiful yield at harvest time. The natural rays maximize plant growth, encouraging quality buds.

The best part of the sun-grown weed is that it produces higher-quality marijuana and fatter buds with better taste.

The chlorophyll in the leaves absorbs the energy from the sun. This process breaks down water and carbon dioxide molecules that produce the energy necessary for the plant to grow.

How much sunlight does a weed plant need a day to receive this energy? Up to 12 hours is sufficient. Sunlight is an important energy source needed to develop healthy roots, branches, and crops.

Those pretty leaves on a marijuana plant are one of the main reasons this crop needs the right amount of sunlight. They have a large surface area, which means enough sunlight absorption needs to take place.

Can weed grow without direct sunlight?

Direct sunlight is by far the most effective way to fulfill the lighting quota of your marijuana plants. Can weed grow without direct sunlight? The answer is complex.

Understanding the difference between direct sunlight and reflected sunlight is essential. At times, growers cannot cultivate their crops in open spaces.

In this case, you may divert sunlight to your sun-grown cannabis by using a reflector.

With an outdoor grow in partial shade, the crop still seeks the sunlight and can develop long awry branches. The development of the bud is compromised, the yield is less, and so is the resin.

Weed can be grown without direct sunlight, with caution.

How does sunlight differ from artificial light for cannabis plants?

When cultivating marijuana, both lighting methods are optional. It all depends on grower preference.

Whether you choose to use artificial ones indoors or rely on the natural rays, one constant question remains: how many hours of light does a weed plant need? No matter the difference between them, cannabis crops still need the right amount of light to feed their growth.

Let’s compare the two in a brief outline:

Sunlight Artificial light
Free—uses UV illumination from the sun Not free—uses fluorescent, LED, and HID lights
Used for outdoor growing Used for indoor growing
Uncontrolled lighting exposure Controlled lighting exposure
Provides plants with natural full-spectrum lighting Mimics full-spectrum lighting
Sun-grown cannabis does well with 10–12 hours of sunlight Cannabis grown with artificial lights needs up to 18 hours of exposure

Weed outside

How much sunlight does a weed plant need?

Several factors determine how much sunlight you should give your weed. How much sunlight does a weed plant need a day is one of them.

It would be quite interesting to compare how different autoflowering and photoperiod strains react to the different amounts of sunlight each needs.

Let’s discuss a few of the most common factors which can help us determine this.

For photoperiod strains

Photoperiod strains are standard feminized seeds that are sensitive to light cycles. How much sun does this marijuana need?

Photoperiod seeds have two phases in their life cycle which can help answer this question:

During the vegetative phase, crops require about 18 hours of daily sunlight. During this stage, the weed starts developing its roots and branches only.

For the sun-grown cannabis to progress to the flowering stage, sunlight absorption requirements drop to 12 hours daily. It’s vital to know that the other 12 hours of the day, the marijuana plants need to be in uninterrupted darkness.

The crops remain in the vegetative stage for as long as it gets 15 hours or more of sunlight per day. These plants need “short days” with a lot of sunlight and “long nights” with darkness.

For autoflowering strains

It’s rather amazing how opposite autoflowering strains are to that of the photoperiod ones. How much sun does this marijuana need? As much as possible.

These wonder seeds can receive as much as 24 hours of continuous sunlight. There’s no such thing as too much sunlight for autoflowering seeds.

Growers favor autoflowering cannabis strains, which have become popular sun-grown cannabis because they can be grown in almost any condition. It also doesn’t need uninterrupted hours of darkness for it to start its flowering process.

These crops grow to produce bushier buds with a much better yield, provided that it receives the right amount of sunlight.

How many hours of light does a weed plant need per day?

How many hours of light does a weed plant need a day? In a worst-case scenario, marijuana plants generally require up to 13 hours of light per day.

The correct amount of light that crops thrive on for growth are:

  • Vegetative stage: minimum of 18–24 hours per day
  • Flowering stage: minimum of 12 hours per day

The amount that weed plants require depends on a variety of factors:

  • Seed type
  • Location of seedlings
  • Stage of growth that your cannabis plant is at

How much direct sunlight does a weed plant need

Do you wonder how much direct sunlight a weed plant needs per day? Cannabis crops are happiest when they receive the right amount.

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Weed plants should receive 10–12 hours of direct sun daily. No problem if your crops aren’t growing in a space where it doesn’t receive direct sunlight. Make sure that it receives approximately 6 hours of uninterrupted reflected sun.

Can weed grow without direct sunlight? If crops don’t receive any UV rays (directly or reflected), they grow slower and provide smaller yields. Get rid of branches and any obstruction to enhance light exposure.

What’s the difference between sunlight in the equator and the hemispheres?

Are you curious about how much sunlight plants need when grown close to the equator? Your location on either hemisphere is crucial since your location impacts how your crops grow.

Being close to the equator and receiving the sunlight from either side of the hemispheres influences the amount of outdoor plant light received by cannabis crops. When the Northern Hemisphere is closest to the sun, it’s called the summer solstice. Growers in this region experience their summer in June.

The germination of your sun-grown weed seeds should be between the start of spring in early March and summer. In the Southern Hemisphere, the earth faces the sun in December. Growers should start cultivating their seeds in early September.

How many hours of light a weed plant needs is usually not a concern for growers who live near the equator. Sun-grown weed flourishes at the equator, offering cultivators the opportunity to grow crops year-round.

The positioning of the equator from the sun never changes. It remains at the same distance, which means it gets 12 hours of sunlight daily. That’s music to a grower’s ears.


Knowledge is power. The information regarding marijuana cultivation is vast. While we have covered some of the most important facts, some frequently asked questions are common amongst growers.

Can weed plants get too much sunlight?

With the keyword being sunlight, the answer isn’t quite simple. Sun-grown cannabis thrives on the energy it receives from the sun to grow, so that’s a no. Considering the strains that need darkness to flower, too much sunlight would be a yes.

Do weed plants need light or heat?

Your sun-grown weed needs both. Sunlight is a source of light and heat. It’s important to remember that since your crops need a lot of sunlight to grow, it’s also receiving heat simultaneously. Keeping the temperatures regulated is a must for cannabis cultivation.

How long can weed plants go without light?

It’s dependent on the strain you’re growing and your sun-grown cannabis plant’s growth stage. It can’t go without light for extended periods. The longest your crop can go without uninterrupted light absorption is 24 hours. It won’t die instantly but may become stressed.

Weed under sunlight

Sun nourished weed!

Who knew that so many intricate details go into growing weed. It makes harvesting those buds a proud moment. Knowing how much sun marijuana needs helps you to optimize your crop’s yield.

The amount of sunlight that your crops receive depends on various considerations that might seem minor but play a vital role.

A question like how much direct sunlight does my weed plant need daily guides you with the decisions you need to make to sustain a generous yield.

There are multiple lighting options available to grow your weed, but direct sunlight is still the best one available.

Now that you’ve learned about the amount of direct sunlight marijuana crops need, why not put your newly acquired knowledge to the test? Head over to Homegrown Cannabis Co. and check out the wide selection of seeds available.

When can seedlings be put under lights or in the sun?

Not sure whether to grow your cannabis seeds in the sun or under lights? This article explains how much light you need, how to prevent your seedlings from falling over, and when to plant them outside.

“When can cannabis seedlings be put under lights or in the sun?” is a common and sensible question that is often asked by novice cannabis enthusiasts after germinating seeds indoors under lights.

For those who are growing indoors, cannabis seedlings may be put under lights as soon as they emerge from the soil or growing medium.

How much light for cannabis seedlings?

When using HID lighting (usually a metal halide lamp), young seedlings should be kept at least 50cm from the bulb.

With compact fluorescent lamps (usually 100w or more), a distance of around 15cm should be maintained between the top of the young seedlings and the bulb.

If using normal fluorescent tubes (18-36w), seedlings can be kept within a few centimetres of the light source.

Cannabis seedlings growing under lights should always be given a gentle breeze from an oscillating fan (a small household fan on the lowest setting is fine), as constant gentle movement will strengthen their stems significantly.

Are your cannabis seedlings falling over?

If cannabis seedlings grow tall and then fall over, this is almost always a result of growing in an environment with static air.

Seedlings intended for outdoor growing should be kept by a sunny window for the first week or two after emerging from the soil.

When they have grown their second or third set of serrated leaves (after the the round cotyledons that initially emerge from the seed) seedlings are usually hardy enough to flourish in direct sunlight.

When to plant your cannabis seedlings outside?

If outdoor temperatures are suitable, seedlings may be acclimatised to direct sunlight by giving them progressively longer daily exposure to outdoor conditions.

Starting with about three hours outside, at the sunniest time of day, seedlings can be given an extra hour of outside exposure each day, so that within about two weeks they can be left outdoors permanently.

Laws and regulations regarding cannabis cultivation differ from country to country. Sensi Seeds therefore strongly advises you to check your local laws and regulations. Do not act in conflict with the law.

Cannabis seedling stage

Keeping your marijuana happy and healthy comes down to how carefully you care for them through each stage of a marijuana plant’s life. Factors such as how much light should seedlings get should be carefully considered as these are especially important in the younger stages of your plant’s life when they are at their most fragile condition.

A marijuana seed that sprouts will split along the seam that joins the halves of its husk. Driven by gravity , the tail grows longer rapidly, screwing its way down into the soil until the root can supply sufficient leverage to raise the husk containing the two seed halves upright.

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From that position, the two halves fold out to act as biological solar panels that gather energy and begin a marijuana plant’s first chlorophyll production even as the tiny taproot sprouts hairlike feeder roots that stretch outward to strengthen its grip in the soil.

In this article, we take a look at the ways to protect your seedlings through their most delicate stage of life.

Our guide to the seedling stage for marijuana plants:

What are seedlings?

The key thing to do during this stage is simply to pay attention and keep tabs on every development or change that occurs in your marijuana seeds. When they sprout, the seeds’ seams will split and allow a white tendril to poke through within several hours of this split. This tendril will grow very quickly, moving downward until it’s deep enough for it to hold up the rest of the plant (namely the stalk and the seed husk).

The husk, now split into two, emerges from the ground and functions as a sort of makeshift leaf – in other words, it absorbs energy that can be used to produce chlorophyll within the plant. While you see the stalk growing upwards, you can also be sure that more roots are sprouting and growing downwards at the same time.

Grab my free Grow Bible for more on marijuana seedlings here

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The first two leaves, completely unique from any future leaves that will grow, pop out of the middle of the seed’s split. These leaves are called sucker leaves and mark the beginning of more leaf growth.

Two-lobed leaves will then grow from the middle of the sucker leaves. These two-lobed leaves usually resemble chicken feet, since they have three lobes. After the three-lobed leaves come two leaves with five lobes, and then two more with seven. Seven-lobed leaves are the ones everyone recognizes as the marijuana leaves.

Two lobed leaves will then grow from the middle of the sucker leaves. These two-lobed leaves usually resemble chicken feet, since they have three lobes. After the three-lobed leaves come two leaves with five lobes, and then two more with seven. Seven-lobed leaves are the ones everyone recognizes as the marijuana leaves.

If you were able to keep your marijuana plants healthy throughout its entire sprouting stage, they would most likely go through a very productive vegetative stage. Protecting your young plants is about more than just survival: it’s about investment in your future harvest.

Also read the article How to germinate marijuana seeds for more about germinating tips

This article covers the various elements you will need to keep a constant eye on to ensure the well being of your seedlings. These elements are protection, water, nutrients, heat, and sunlight.

How to protect seedlings

You will need to protect your young plants from more than just discovery by the authorities. Even if you live in a location where growing marijuana is legal, you have plenty to worry about with protecting your seedlings.

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You should keep your plants in some sort of protected area, such as a rooftop, and shelter it using some sort of a transparent, plastic dome or bubble. These domes can keep your seedlings from being eaten by insects, rodents, or other pests, and they are easy and cheap to make yourself.

Simply slice a clear plastic bottle in half, then recycle the top half and keep the bottom half. You should cut small slots around the edges of this half so that your young plant will have some airflow. Place the dome over your little plant, completely covering it. This will have the additional bonus of insulating your plant in case an unexpected frost occurs. In my free Grow Bible, you will find more DIY hacks for your grow.

In addition to insulation and protection, your seedlings will need the most important elements on Earth: water and sunlight. You have to constantly keep the soil and the seedling moist around the clock, and you need to make sure they are receiving plenty of sunlight.

If you live further north, you could have some more trouble with this since your spring days will be shorter than latitudes further south. One big problem that can happen to outdoor growers is their seedlings not receiving enough sunlight. When this happens, the plant stretches taller and taller in an attempt to reach more sunlight, and then it is too tall to hold itself up any longer.

If you want to keep your grow small I can advise a solution like a Pot for Pot. They offer an all-in-one box with everything your plant will need.

If you have space and resources, you can try sprouting your cannabis seeds inside of a closet to begin with. Using the proper equipment in this environment can give your young plants plenty of sunlight, giving them enough energy to sprout large, healthy leaves right from the beginning.

This type of growing would also ensure that their stems won’t get too long and weak; rather, they will be short and strong. You will be able to avoid the hassle of stabilizing tall, weak stems with sticks. If they don’t do this while the plant has leaned to the ground, it could begin to rot.

That being said, if you start to grow your seedlings indoors, transplanting them later will be necessary, which presents its own difficulties and safety concerns for your young plants. Ultimately, it depends on which option is best for you.

How much water do seedlings need

One common problem that occurs when trying to care for a seedling is giving them too much water. It is actually less of an issue having to do with too much water, but actually has more to do with too little oxygen reaching your plant’s roots. This happens most commonly with seedlings being grown in containers since water can only go so far as the walls of the container.

If your plants are being overwatered, you will most likely see symptoms such as drooping leaves. There are plenty of ways to avoid this, however, as long as you keep reading for a better understanding. Your planting situation is the most important factor that comes into play when considering how you have managed to overwater your plants, and how you can fix or avoid the issue.

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Overwatering your seeds

Your pot is too big for your seedling

Since a young plant’s tiny roots absorb much less water than their more mature counterparts. If you water as much as the container can hold, these tender roots will not be capable of taking it all in. This situation occasionally referred to as “overpotting,” leads to overwatering. So how do you prevent this situation from happening?

The best thing to do is to begin your seedling’s life in a smaller container to begin with. Once they have grown a fair amount, you can move them to a bigger container. If it’s too late and you need to fix the issue, simply direct your watering to a specific area: a little circle right around your plant. Once the topmost inch of soil is dry again, you can do another round of watering. You can only begin watering normally.

If you plan well enough in advance, you can have a separate container for each of your marijuana plants’ stages of life. If your plants will be living in containers for the entire growing season, you will need to know in advance the size of your last container.

In other words, you will have to have a good idea of how large you would like your plants to become. Because roots grow more rapidly when they are left in one container for a long time, fewer transplants mean a larger size plant (and therefore container). Take that into account when planning your container sizes.

Your pot is too small for your seedling

You can plant seedlings in very small individual containers, such as a solo cup. You can’t keep them cooped up in a solo cup forever, though since their roots will quickly outgrow the small space. If your plants are left in a small container for too long, they will become “root bound.” This means that the roots have wrapped themselves around the outside of the cup, keeping water on the inside from escaping.

Why is being root bound such a bad thing? It can lead to some pretty big problems, including overwatering, nutrient deficiencies, wilting, and more. You can avoid this problem simply by changing the size of their containers as frequently as necessary. (Use these containers)

Poor drainage

If your plants’ container does not have an efficient drainage system (i.e. holes punched in the bottom of the container, plus the right kind of soil), overwatering will quickly become a problem that could be life-threatening to your plants.

One way to keep this from happening is to start growing your plants in a soil that drains well from the very beginning. Soils that are clay-based, for instance, retain water and, therefore, should be avoided.

You can also begin with a smaller container, which would help prevent the issue that was mentioned above. Make sure your container has lots of holes where water can drain from.

If you ever notice that water isn’t draining as fast as it should, you can add perlite to your soil to increase the oxygen content. Don’t water your plants quite as often until you notice them drinking more, or try using a Smart Pot instead of a normal pot.

If you follow these tips and are careful about watering your plants, you should be able to avoid overwatering them altogether.


If you’re sure you haven’t been watering your plants too often or too much and they are drooping or wilting, the culprit could actually be a lack of water. Sometimes people who know about the common occurrence of overwatering seedlings have overcompensated, therefore actually watering their plants less than is required.

The roots of your plants need to constantly be able to access water. Plants lose the water they have absorbed through their leaves in a process called transpiration. They do this by sucking up the water from the roots like a straw. If this process keeps going and the roots down below are not receiving enough water, the plant will undergo some serious problems.

If you are able to visibly notice your soil separating away from the container it’s in, you probably have an underwatering problem on your hands.

If your soil is enriched with nutrients and you underwater your plants, the effects will be even more devastating. Your plants will turn a dark green color and will have twisted new growths of a strange color. In this case, the only thing you can do is give your plants more water to re-establish their roots and begin growing once again. If they receive enough water to fight these effects, they will probably be able to combat this situation.

What kind of nutrients

Giving your plants nutrients can come with its own issues. If you give your plants too high a dosage of nutrients, for example, it will turn into nutrient toxicity. Your plant’s leaves will have tip burn and turn darker in color.

Nutrient toxicity can be caused by using a “hot” soil or a type of soil with a lot of nutrients. As long as you are watering your seedlings enough, they should be able to grow out of nutrient toxicity that comes from using hot soil.

Some soils are “slow-release,” such as Miracle-Gro. Avoid these soils at all costs, as they will not help your plant be healthier – in fact, it makes them even more susceptible to nutrient toxicity.

If you provide your seedlings with nutrients when they are too young, they might have a sort of nutrient overdose. As long as your initial potting mix is high quality, you shouldn’t need to worry about adding any more until after a minimum of a few weeks.

If you feed your plants with a large amount of nutrients all at once, you could end up with nutrient toxicity in less than a day. If you’re using a nutrient schedule that comes with the store-bought nutrients, half the amount it says and see how your plants react before adding any more.

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