Does a plant grow better in sunlight or artificial light

Do plants grow better in sunlight or artificial light?

Growing plants indoors with artificial light is certainly possible, and there’s a good chance you’re already doing it. Houseplants like ivy are descended from forest bottom dwellers and shade loving plants. They blossom on exposure to natural sunlight but can typically get enough light from a full day’s exposure to your standard fluorescent lights.

The challenge comes in when you’re trying to grow plants that normally need more than what our average artificial lighting level would provide or attempting to stimulate only certain aspects of plant growth.

Sun-loving plants need high intensity light for a full 12 hours or more. If you’re going to grow these plants under artificial lights, you need artificial lights that truly mimic sunlight. There’s a chance you’d need to use halogen lights to meet the needs of these plants, but now you’re going to have to take care not to burn them because halogen lights are so hot.

If you’re trying to grow sprouts, including sprouts for adding to your sandwich, you’ll want to grow them under red lights. If you want to start your seedlings indoors to get a jump start on the growing season, with the intent to transplant them outside later, you’ll want to grow these under red light.

Plants that are grown entirely under red light tend to be tall and spindly – great for salad sprouts and seedlings that will be outside soon. Red light should be the dominant color spectrum if you’re trying to grow tubers and bulbs. Are you trying to develop fruit like tomatoes and berries? Then you want strong red light exposure.

You’ll need something with more red spectrum than incandescent lights, though incandescent lights already provide a high level of red wavelengths. The problem with incandescent bulbs is that they also generate a lot of heat, so putting a plant close to the bulb to give it the most light risks sun-burning it. If the plant is far enough away not to overheat, then you can use standard incandescent bulbs to help them fruit and bloom.

If you want the plant to grow more heads and stems, you’ll want it under at least some blue light. However, even red lights missing the far red spectrum will result in more compact growth than if the entire red spectrum is present. However, if you want a basic flowering bush perfect to sell for placement on someone’s desk, this may be perfect for you.

If you’re trying to grow leafy greens like radishes, lettuce, water cress and spinach, you want to grow them mostly under red light. The red light spectrum encourages leaf growth.

Flowering plants that haven’t yet bloomed can be kept under red light to delay their blooming. They register the long days under red light as the long hot summer. Once you shift to shorter days and some blue lights, they see it as autumn blooming season as having arrived and erupt into a flowery show. If the plants are already flowering, adding red and far red light will stimulate further flowering.

There are only a few cases where you want to grow plants under predominantly blue light. Blue light limits the growth of extensions like leaves. If the plant has grown flowers or heads, exposing it to mostly blue light will prevent it from bushing out further. If you’re planting seeds, exposure to blue light will result in more female seeds and female plants. Blue light is especially useful in aquaponics systems where you’re trying to raise algae and coral.

Fluorescent light bulbs are already biased toward the blue spectrum. A cool white fluorescent bulb, though, covers the entire spectrum. This is why cool white fluorescent bulbs are a good choice for general lighting for indoor growing plants indoors with artificial light.

Note that when you aren’t try to optimize plant growth in some way like trying to maximize leaf growth or the number of flowers, you don’t have to worry about the red-blue spectrum. Instead, simply find artificial lights like Led grow lights that provide the entire spectrum of light. This means that many readily available artificial lights can be used for houseplants or plants you’ve temporarily brought indoors. Or you could use horticultural growing lights that by design provide the entire spectrum.

The Benefits of Sunlight Vs. Artificial Light for Plant Growth

coral cactus image by Ray Kasprzak from

All plants need light to grow. Plants use light to create the energy needed to make the food they need to grow and a plant’s growth rate and longevity is dependent upon how much light it receives, according to the Texas A&M Agricultural Extension website. Living in a house or apartment with limited access to sunlight does not mean you cannot grow plants. Artificial lights can be used to supplement natural sunlight or, in some cases, replace it completely.


Sunlight is the best light for plants. The rainbow effect created by holding a prism up to sunlight is a visual description of the colors in the light spectrum. Plants need the red and blue parts of the light spectrum, with red being more important than blue. Indoor plants placed within 10 feet of a sunny window receive the natural balance of red and blue rays they need.

Artificial Light

Artificial light allows plants to be grown anywhere in a home; however, not every light bulb will suffice. Improper light exposure can result in weak, spindly plants with pale leaves, whereas exposure to proper lighting can produce plants with shorter, stronger branches of dark green leaves.

A simple incandescent light does not meet a plant’s requirements. They provide the red rays that plants need, but not the blue; in addition, incandescent lights create excessive heat. Fluorescent light tubes are a good source for providing light for plants; however, there are a variety of fluorescent tubes. The “cool white” fluorescent tubes, as well as special plant fluorescent lights are selected by many indoor gardeners, according to the University of Missouri.

Light to Plant Spacing

Place plants within 10 feet of a sunny window. After time, the plant will “reach” towards the window; rotating the plant will keep the plant’s shape even.

Plants using only artificial light should have the tips of their leaves placed six to 12 inches from the light. As with sunlight, the plant might “reach” for the light bulb; rotate the plant or place it directly under the light source. Plants should receive 16 to 18 hours of artificial light each day.

Gardeners who start seeds indoors often use artificial light. The seeds’ containers should be placed less than six inches from the light source. As the seeds germinate and grow, move the light source upward to keep it no closer than six inches above the planters.

Does Cannabis Grow Better in Sunlight or Artificial Light?

The longstanding debate continues to rage about whether indoor controlled-environment cannabis grow lighting or outdoor cannabis utilizing natural sunlight is superior. Each camp has its firm and devoted legions that have already made up their minds.

Fortunately, there’s room for both cultivation methods in today’s cannabis space, and one method is unlikely to replace the other. Cannabis requires full sun or artificial radiation to thrive—it’s not a plant that enjoys a lot of shade. It soaks up the rays and grows at a rapid rate. Both natural sunlight and artificial grow lights have their pros and cons. Each is superior to the other in specific ways. Let’s break these down and shine a light on which method will suit your needs best, if that’s an option in your home state.

Natural Sunlight

There’s no replacement for Mother Nature. Sunlight has served the needs of our planet for millennia and shows no signs of letting up anytime soon. Since the cannabis plant does its best with 10 to 12 hours of direct sunlight per day, it soaks up a tremendous amount of solar energy. Access to full, unfiltered sunlight should be the goal of all outdoor cultivators. Sunlight also has the advantage on operational costs since it’s free—and nothing is cheaper than free.

Because cannabis enjoys direct sunlight to grow to its full potential, prolonged periods of shade are undesirable. Commercial cultivators will want a cleared, open field for their grows. A private grower may face more challenges in this area, because unobstructed, 180-degree sunlight can be difficult to provide in a home environment unless the grower has flat roof access or a very large yard. In the Northern Hemisphere, the sun sits in the southern sky. Summer sun—the primary growing season for cannabis—provides advantages because the sun is higher in the sky than other times of the year and the daylight periods are longer. Equatorial sun always stays directly overhead and shadows never grow longer, which is why these areas are well-suited for cannabis. Growers in the U.S. should situate their gardens on south-facing areas for full sun access. Sloped terrain can provide advantages because the cultivator can create a tiered arrangement with rows of plants that have a superior angle for sunlight—as close to equatorial sun as possible in the Northern Hemisphere. Avoid north-facing cultivation sites, because more shows will result, and this is less advantageous for plants.

The sun provides plants with natural full-spectrum lighting that grow lights mimic. The solar radiation that plants rely on for growth is ultra-violet (UV) illumination, a combination of UVA and UVB rays. Plants use and benefit the most from the longer UVA rays. Grow lights do a good job replicating the full-spectrum lighting of the sun for indoor grows. And although it’s difficult to improve on Nature, it’s much easier to control grow lights than outdoor sunlight.

The Uncontrolled Growing Environment

Sunlight can get blocked out by clouds, causing prolonged periods of darkness, which is less than ideal for cannabis. The outdoor growing environment that relies on the sun can also experience periods of wind, rain, and hail, all of which can damage plants. Pests can be another problem outdoors. Deer, rodents, and other animals have been known to devour and damage cannabis, which can have a devastating effect. Insects can be an even greater problem. Some insects and their larvae will decimate lush cannabis flowers to the point that they’re seriously damaged and nearly useless for human use.

These types of uncontrollable variables with outdoor, sunlight-dependent cannabis grows is part of the risk factor that makes some growers opt for indoor cultivation using artificial illumination.

Grow Lights

Does Cannabis Grow Better in Sunlight or Artificial Light?

Plants grown indoors using grow lights must rely on man-made full-spectrum lighting. The most common types of lights used for this purpose are high-pressure sodium (HPS), metal halide (MH), and light-emitting diode (LED) lights.

Metal halide lights emit a whiter light than high-pressure sodium and have a long history of use with cannabis. By today’s standards they are inferior to high-pressure sodium, but they still have applications for cannabis cultivation, especially with young seedlings and young plants in the vegetative stage that are developing root structure.

High-pressure sodium lights emit yellowish orange rays. This type of lighting does an excellent job growing indoor cannabis, particularly during the flowering stage. High-pressure sodium lights are the variety of light that most cannabis cultivators know and love. They are in wide use today in both private home grows and large commercial grows.

Light-emitting diode lights are relative newcomers to the world of indoor cannabis cultivation. These lights are quickly gaining in popularity. While they are more expensive to purchase than other cultivation lights, refinements in manufacturing them has caused prices to come down. Although they initially cost more, they last longer and they use less electricity so they are less expensive to use over the duration of their life compared to other bulbs. In addition, LED lights are safer because they do not get nearly as hot as other bulbs. These factors have caused LED lights to become increasingly popular.

These three popular indoor cultivation lights come in a variety of wattages and designs. The hoods used to maximize their effectiveness vary tremendously. Some have a vertical, domed look, while others have a flatter, horizontal appearance. The most popular wattages are 200, 400, 600, and 1000, although other sizes are widely available. The lower wattages are used mostly by home growers, while the larger 1000-watt and higher wattage lights are favored by commercial growers. The electrical output and limitations of the power source must be compatible with the lights used.

The Controlled Growing Environment

One of the big advantages with grow lights and the indoor growing environment is that the cultivator can control his or her artificial environment. Not only can the intensity and distance of the light be manipulated, but the temperature and humidity can as well. The indoor grower can also provide supplemental CO2, which is impractical and ineffective outdoors.

The controlled indoor environment is also free of risks from pests. No animals or inclement weather will adversely affect the grow and harvest, which is so common outdoors. Light intensity and duration stays constant throughout the entire growing period.

Greenhouses: The Best of Both Worlds?

Utilizing greenhouses for cannabis cultivation is becoming increasingly popular. There are many reasons why this cultivation environment makes sense and has unique benefits. Cannabis cultivators can benefit from the best of both indoor and outdoor cultivation when using a greenhouse.

Greenhouses allow growers to benefit from the sun’s natural light, and plants can thrive in a protected environment. Humidity is easy to control and supplement if necessary, and additional artificial lights can ensure daylight conditions occur when desired year-round. Black-out tarps provide a means for creating nighttime conditions whenever desired. There are many reasons why greenhouses make sense for both home and commercial grows.

Regardless of whether you use a greenhouse, grow outdoors and reap the rewards of natural sunlight, or grow indoors and enjoy the peace of mind of a controlled environment, there’s a cultivation method that’s bound to suit your needs. The choice is yours!

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The Effect of Light on Germination and Seedlings

David Batty explains this important aspect of growing from seed.

Apparently it was custom in Ancient Egypt, before finally sealing the tomb, to leave a little pile of moistened corn near the sarcophagus. One can imagine the seed germinating in the pitch darkness, stretching itself upward feeling for light which was not there and finally toppling over having exhausted its food reserves.

It is a fact of life that most plants need light to grow and keep them healthy, but not all plants need light to germinate, and, as we shall see, some seeds find light a hindrance. If we look at the matter from the gardener’s point of view, however, we can use the rule of thumb that most cultivated plants on sale in seed form prefer to germinate in the dark. There are some notable exceptions however, some greenhouse perennials, epiphytes, many grasses, and even tobacco all prefer light and a large number of seeds are not fussy either way.

The reason is that commercially produced seed is bred and selected for its ease of germination as well as other more obvious characteristics and so peculiarities such as light or dark requirements do not often occur. On the other hand seed which is obtained non-commercially, in small quantities from the home gardener, seed lists, or the more unusual items from seed merchants may prove to be much more fussy in its requirements. In fact, research has shown that with seeds other than cultivated forms there is a great deal of variation. We can divide seeds of this type into those which germinate only in the dark, those which germinate only in continuous light, those which germinate after being given only a brief amount of light and those which germinate just as happily in light or darkness.

As long ago as 1926 experiments were carried out by Kinzel to find out the light requirements of hundreds of plant species. He found about 270 species which germinated at or above 20°C (60°F) in light, and 114 species germinated at the same temperature in the dark. He also found 190 species which germinate in light after experiencing hard frosts and 81 species likewise germinated in the dark. Fifty-two species germinated in the light and 32 species in the dark after light frosting and finally there were 33 species which were unaffected by light or dark.

Unfortunately, as with all gardening matters, things are not quite this simple. Other factors, it seems, can also affect the seed’s light requirements, for example, with some species (e.g. Salvia pratensis and Saxifraga caespitosa) light requirement only exists immediately after harvesting whereas with Salvia verticillata and Apium graveolens (Celery) this lasts for a year and to confuse matters further other species develop a light requirement while in storage. Chemicals also, such as nitrates in the soil, can substitute for light in stimulating seeds to germinate so that some light requiring seeds will still germinate if covered with fertile soil. Still it all makes for interesting gardening doesn’t it?

For a fairly comprehensive list of the Light/Dark requirements of seeds we refer you to Thompson & Morgan’s booklet ‘The Seed Sowing Guide’, which they will be pleased to send you for only 99p if you drop them a line. This is a helpful general guide but it is worth remembering that not all seeds in the same genus behave in the same way. For example Primula ohconia needs light and Primula spectablis needs darkness for germination, so there is still a lot to learn, much of which can only be gained by personal experience and sharing that information gained with others.

The explanation of how light affects some seeds and causes them to be in a state of readiness for germination and yet prevents other seeds if necessary from germinating is highly complex. Suffice it to say that it is mainly the light’s effect upon a plant pigment called phytochrome within the seed. This relates to the type of light which the seed receives. As a generalisation, light in the red wave length usually promotes germination whereas blue light inhibits it.

In a practical vein the light requirements of a seed may relate to the habitat in which the seed parent usually grows, so as to ensure that those which fall in an area conducive to growth will germinate and those which fall in less salubrious circumstances bide their time. For example a seed requiring light to germinate might fall into the deep shade of another plant where growing conditions would be very poor, whereas a seed falling into an open, well lit space would germinate quickly and flourish. On the other hand, it may be essential for the establishment of the young seedling that part or all the seed needs to be covered with soil or in the shade, perhaps, to protect the young root.

In such a case with a seed which required darkness, uncovered seed, which is exposed to light will not germinate. Sometimes only part of the seed is light sensitive. Phacelia is light sensitive at only two points on its surface and in a lettuce at only one. The micropyle where the water is absorbed, is light sensitive perhaps to ensure that only correctly oriented seed with the best chance of survival germinates.

Of course, the effect of light on seeds should not be over emphasised, no real hard and fast rules can be laid down, as other factors interact with light. To the gardener, the two questions he needs to have answered are ‘How deep should I sow my seed?’ and ‘Should I cover the seed tray to exclude light or not?’

In answer to the first question, depth of sowing depends a lot upon the size of the seed. Very tiny seed should normally be sown and left uncovered. Small seed which needs light will usually receive it even if you cover it with a light sprinkling of compost or vermiculite because light does travel a short distance through the soil and with some seeds exposure does not need to be long or continuous. For example tobacco seed receives all the light it needs to germinate, after it has taken up water, in 0.01 seconds of sunlight and even moonlight will do!

It is not just the very tiny seeds which sometimes need light to germinate, an average seed like Impatiens is light sensitive too and should be covered with a fine sprinkling of vermiculite after sowing and left in diffused light, placed in polythene to provide a high humidity until germination which usually takes 10-14 days at 21-42°C (70-75°F).

Medium sized seeds and upward, unless they have a light requirements (and we do not know of any really large seeds which do) should generally be sown just below the surface, enclosed in a polythene bag or cling film and placed in diffused light.

Some, but not all, popular seeds which prefer light for germination are: Achillea, Alyssum, Antirrhinum, Begonia, Calceolaria, Coleus, Exacum, Ficus, Gaiilardia, Gerbera, Gloxinia, Helichrysiim, Kalanchoe, Nicotiana, Petunia, most Primula, Saintpauliu and Streptocarpus.

Seeds which will only germinate in darkness should be sown at the correct depth and then covered in black plastic or similar to exclude all light until germination takes place. Cyclamen is a subject which should be treated in this way. Normally a difficult subject to germinate it proves far less so if sandwiched between moist filter paper and placed in a plastic container in total darkness. Usually germination occurs in about a month at 15-20°C (60-68°F) when the tiny corms can be transplanted into compost and grown on. The temperature, however, should be no higher than 20″C (68T) as high temperatures will induce a different form of dormancy!

Some other popular types which prefer darkness for germination are: Calendula, Centaurea, Delphinium, Gazania, Nemesia, Primula sinensis, and Schizanthus.

Providing artificial light should not normally be necessary for seeds sown in greenhouses, well lit propagators etc. but if light is a problem or, more importantly, if you want to ensure rapid, healthy growth of your seedlings after germination then some form of additional light may be necessary. This would particularly be the case in raising seeds early in the season and quite a number of flower and vegetable seedlings respond to supplementary light. For example, tomatoes and cucumbers where vigour and earliness have been improved, also Antirrhinum, Stocks, Gerbera, Gloxinia and Gesnaria have all responded with a higher growth rate when given extra light in the winter months.

Tuberous begonias when sown in late winter must have supplementary lighting if they are to develop properly. They are sensitive to day length and when this is less than 12 hours they form tubers instead of making vegetative growth. In order, therefore to produce healthy young plants lighting must be given to extended the day lengths to more than 12 hours.

To provide this light, fluorescent tubes of the Gro-Lux type, to give light something akin to sunlight should be used, suspended around 2 feet (60cm) above the seedlings. As there will be so much moisture about use only approved horticultural fittings when installing the lights and fit a time clock if possible so that the lights can be on for 12 hours each day.

David Batty is a former Technical Manager at Thompson and Morgan Seeds, where he looked after the seed-testing laboratories.

Source of article
Growing From Seed – Spring 1989 Vol. 3 Number 2
© The Seed Raising Journal from Thompson & Morgan

Why do some seeds germinate only in the dark?

It may be easier to answer the question “Why are some seeds inhibited from germination when in the light”.

The key to this phenomenon is Phytochrome and you need to research that pigment and its different forms to write a full explanation. You will also need to find out about RED and FAR-RED light.

Phytochrome is present in one form in white/sun light and present in a different form after a period in the dark. Normally, the light form decays to the dark form after a few HOURS, but it is converted back again after a few MINUTES in the light. So, a seed on the soil surface gets enough light to keep the dark form of phytochrome low for sufficient time to prevent germination initiation. It is only when the seed is in permanent darkness that the dark form of phytochrome is active for long enough to trigger germination.

Obviously, this prevents such seeds germinating until they are buried.

This mechanism is even more interesting … some seeds will ONLY germinate in the light (I know these are NOT the seeds you asked about), but if the light has first passed through leaves, then germination is inhibited. This enables such seeds to germinate as soon as they receive direct sunlight, but to remain dormant whilst they are under other plants which would give a developing seeding too much competition. It turns out that the spectral quality of light that has passed through leaves is such that it converts the phytochrome to the ‘dark’ form (as I have called it) – even though the seed is on the surface of the soil.

I hope you will find this a fascinating area to research.

Cannabis seeds are expensive.

You want to make sure they sprout, because any seeds that go to waste cost you a lot of money.

To maximize the chance of success, seeds need the right conditions.

They need the right amount of light, the correct temperature and the correct amount of moisture.

If you provide what they want, the changes of successful germination skyrocket.

If you do not provide the ideal conditions, the chances of success plummet.

We’ll tell you exactly what you need to do to give your weed seeds the best chance at becoming a strong and healthy marijuana plant. And we’ll start with the question that likely brought you here: the light requirements.

Note: if you’re looking to buy seeds, we don’t sell them, but we recommend this store (they have a germination guarantee, which is a nice touch). We caution against using bag seed.

How Much Light Do Cannabis Seeds Need?

Cannabis seeds need no light when they are germinating. In fact, they require an absence of light. All of the methods below call for darkness.

Once they have sprouted, they will need a lot of light—18 hours a day, to be exact (though you could even give them 24 hours of light per day).

How To Germinate Cannabis Seeds

There are several methods for germinating marijuana seeds, each with their pros and cons. We will cover the best methods below, with the first method offering the best chance of success and the last one offering the lowest chance.

These seeds are expensive, so we recommend using the method with the best chance of success, so you reduce the risk of wasting seeds as much as you possibly can.

Germinating Cannabis Seeds In A Propagator With Peat Pellets

You get the highest success rate when you provide the perfect environment for germination. A propagator ensures optimal control over the environment.

  • best chance of success
  • once you have the propagator, you can keep reusing it
  • need for equipment/higher startup cost
  • not as simple as some other methods

There are various types of propagator on the market: some just have a plastic dome, some have seed starter trays, some have heating pads and some even include a grow light. Here is a low cost propagator that includes a seed starter tray.

Fill each hole in the seed tray with a peat pellet. You can buy them at any garden store or get them online. This bag of pellets from Jiffy is a great deal.

To use the pellets, simply soak them in water for around ten minutes. They will expand.

Once expanded, poke a little hole about half an inch (1.5 cm) deep into each pellet. Place one seed in each of the pellets and cover the seed up. It needs to be beneath the soil in darkness.

Make sure you keep the propagator warm, at a temperature of 68° to 82° F (20° to 28° C) and the seed pellets moist. They can never dry out or the seed will die.

Note that peat pellets are great for planting in soil or coco coir, but they do not work with a hydroponic setup. For that, you should use rapid rooters.

Rapid rooters actually work great for any type of setup, but we prefer peat pellets for non-hydroponic setups, because they cost less and they do not dry out (since rapid rooters come in bags of 50 or more, if you do not use all 50 fairly soon, the remaining ones will dry out and become useless, though you can reseal them to give yourself a bit more time).

Whether using peat pellets or rapid rooters, this method ensures a high rate of success, but it does require the purchase of a propagator and the pellets or rapid rooters.

You can save a bit of money by skipping the propagator and just rigging something up yourself (or not using any type of covering at all), which is what we’ll cover next.

Using Peat Pellets With No Propagator (Or With A DIY Propagator)

If you are on a bit of a budget, you can forgo the propagator and just use peat pellets on their own. You could even make a DIY propagator by simply using some kind of plastic cover.

  • lower cost than using propagator
  • peat pellets (or rapid rooters) still offer the best chance of success, even without a propagator
  • less control than with propagator
  • if using a DIY propagator, requires time to construct

A great DIY solution is to use simple plastic cups, one for each peat pellet. Cut the top off a small plastic drink bottle and place it over the peat pellet with the seed as a dome.

But you don’t need any propagator at all.

Covering the seeds helps keep in the moisture and makes it easier to keep them warm, but it is not necessary. You can just as easily keep the peat pellets uncovered, as long as you ensure they stay moist and are kept in the correct temperature range.

Germinating Cannabis Seeds Using Paper Towels

This is probably the most written about method, but that does not make it the best. It is easy and you won’t need any additional equipment, but it requires handling the delicate seedling.

  • very easy
  • no additional equipment required (assuming you have paper towels)
  • requires transplanting the seeds, which risks damage
  • need to ensure the paper towel stays damp, but not wet

The only thing you need for this method is a paper towel, although I would also recommend using two plates.

For the paper towel, you actually want to use the cheapest brands. More expensive towels are more porous, which makes it easier for the delicate root to get stuck and tear off when transplanting the seedling.

For this method, place a paper towel on a plate and get it nice and wet. Drain off any excess water, though. It should be damp, but there should be no standing water or the seeds can drown.

Put your seeds on one half of the paper towel and fold the other half over them, so that they are covered. Then take the second plate and put it upside down on the bottom one, forming a dark cavern between the two plates for the seed to germinate.

Check once or twice a day to ensure that the paper towel never dries out. If you need to add water, make sure that you always drain out any standing water. Keep the seeds covered and at the correct temperature. They should sprout in a few days.

Once they have sprouted, you’ll want to transfer them to soil or a growing medium. See below for instructions on how to do this.

Germinating Weed Seeds In Soil

This method is the easiest, since you simply let the seeds germinate in the same place where they will grow afterward. Not having to transplant the seed after it sprouts means you don’t risk damaging it causing it shock that will slow growth. The main drawback is a lower success rate.

  • easiest method
  • no transplanting required
  • no additional equipment required
  • lower success rate than other methods

All you do for this method is poke a hole in the soil or growing medium that is about half an inch deep (1.5 cm). Place the seed in the hole and cover it up. Ensure that the soil or growing medium is moist, but not soaking wet. The temperature needs to be in the correct range as well.

Germinating Marijuana Seeds In Water

This is another easy method, but it does require transplanting the seeds once they have sprouted.

  • very easy
  • no additional equipment required
  • lower success rate
  • often seeds will not sprout in time and you will need to use a different method as a backup (or lose the seed)

For this method, simply fill a glass with warm water and drop the seeds inside. Store in a dark and warm place for 12 to 24 hours.

You should see the tap root poking out of the seeds by then. If not, you’ll want to continue germinating the seeds elsewhere, perhaps in soil. If they are submerged in water for more than 24 hours, there is a risk that the seeds can drown.

My Seeds Germinated, Now What?

Once the seeds have germinated, it is time to transplant them into soil or a growing medium. Be very careful not to damage the delicate taproot. Ideally, use tweezers to handle the seeds, to avoid any oils from your fingers doing any damage.

Plant the seeds about 1 to 2 cm deep, so that it does not require too much energy for the stem and first leaves to pop up through the soil.

Make sure the soil is moist and the seeds are kept at the correct temperature of 68° to 82° F (20° to 28° C). Your little plants should pop out of the soil within a few days.

At this point, the seeds will want light, and lots of it. Even if they are still beneath the soil, you can go ahead and turn on your grow light.

If you do not have a grow light, there are a number of different types you can consider. For seedlings, fluorescent lights or LED light bars (like the veg/clone bars from Secret Jardin) are ideal, unless you are germinating a lot of seeds at once. Then you might want to consider a larger LED grow light.

Best LED Grow Lights For Starting Seeds

The best LED grow light for seedlings is the NextLight Veg8. It was especially designed for seedlings, clones and vegging, with a separate “clone” mode for clones and seedlings. The main drawback is that it is made to cover a 2 by 4 foot area. If you only have a few seedlings, this light will be overkill.

LED bars are the best LED lights for seed starting when you don’t have enough seedlings to fill a 2 by 4 foot area. These bars from Secret Jardin are a great choice. They are inexpensive and give off enough light to get your plants through the seedling stage in no time.

HPS Or MH For Seedlings

You can put seedlings under HPS or MH light, but I would only suggest this if you already have the lights. It is more cost effective to use LED or fluorescent lights.

The only time MH or HPS really makes sense is if you keep your plants in the same space from seed to harvest, i.e. you do not have a separate area for seedlings.

Metal halide light is better for seedlings than HPS light, since they need cooler light with more blue light than red.

When To Put Seedlings Under MH or HPS

You can turn the grow light on once the seeds have sprouted and they are in the soil or growing medium. Even if the plant is still not visible, the heat from the grow light will actually help warm the soil, which encourages the plant to grow.

How Long From Seedling To Vegetative

It usually takes from 10 to 15 days for seedlings to transition to vegetative growth, but it is difficult to give an exact timeline. It just varies so much from one strain to the next and from one growing environment to the next.

How Long Do Weed Seeds Last?

If stored correctly, marijuana seeds could last up to 5 or 6 years. That said, the older they get, the lower the chance of successful germination and the longer it takes, even if it is successful.

To store your seeds for the best results, keep them in a cool, dark place. A basement works well, as does a refrigerator.

Where To Get Seeds

We often get customers asking to buy seeds from us. Unfortunately, we do not sell seeds ourselves, but we highly recommend the seed store from I love Growing Marijuana.

You can find it here.

They have a huge selection of quality seeds and their prices are excellent, especially when you snag one of their deals.

Cannabis Light Schedules: Vegetative Stage vs Flowering Stage

by Nebula Haze

Cannabis plants keep getting bigger and bigger with long days, and start making buds when you give them long nights.

Cannabis is a “photoperiod” plant, which means the amount of light received each day decides when the plant starts flowering or making buds. This article explains how much light a day your photoperiod cannabis plants need to grow and start budding, so you get to a happy harvest day. What about auto-flowering strains?

  1. Vegetative – Seedling or clone leads to Vegetative Stage –
    Give 18-24 hours of light a day

  2. Flowering – Flowering (Budding) Stage leads to Harvest –
    Give 12 hours light & 12 hours dark each day

Seedling or Clone

While not technically a “stage,” all grows start with cannabis seeds or clones.


Plant your seeds or clones when you’re ready to start growing! What are clones?

How to germinate seeds:


Some outdoor growers start their plants indoors to give them a headstart before putting plants outside.

If you’re growing cannabis outdoors with seeds, you should wait until a few weeks after the spring equinox to put your seeds outside. In the northern hemisphere this means seeds go outside in-or-after April, In the southern hemisphere seeds go outside in-or-after October.

For growers starting with cannabis clones, generally you should wait a few weeks longer than with seeds. Cannabis clones are more prone to flowering early outdoors than seeds, so you might want to put your clones out in late Spring or early Summer. (What are clones?)

If you live in a cold climate, you must also wait until after the last frost before putting your plants outside. Freezing temps will kill cannabis plants. Strain choice is very important. Some strains flower earlier than others. For outdoor growers in cold climates, it’s important to make sure you grow a strain that is matched up with your local weather, so that plants are ready for harvest before temperatures drop.

Vegetative Stage

The vegetative stage is one of the most important parts of the life of your cannabis plant.

The vegetative stage is the growing stage of the plant. When in veg, cannabis plants grow bigger and taller, growing only stems and leaves. As a grower, you are able to control the size and shape of your plants in the vegetative stage using simple training methods.

During the entire vegetative stage the plant does not produce buds at all. It only grows stems and leaves. During the vegetative stage plants tend to grow very fast, especially when conditions are right.

What keeps cannabis in the vegetative stage?

Short nights keep cannabis plants in the vegetative stage. You can keep a cannabis plant in the vegetative stage for basically forever as long as the plant continues to get short nights (shorter than 1s-12 hours, depending on the strain).

Cannabis will stay in the vegetative stage as long as the plant gets short nights (less than 11-12 hours of darkness each day)

Whether you’re growing indoors or outdoors, you must make sure your cannabis plants get at least 13 hours of light each day to stay in the vegetative stage. If your plant gets a few long nights, it may start budding before you want.

The plant can receive as much as 24 hours of light a day while in the vegetative stage. Many indoor growers provide 18-24 hours of light a day (known as 18-6 or 24-0 light schedules) during the vegetative stage to encourage faster vegetative growth.

Don’t want to worry about light schedules? For growers that don’t want to pay attention to light schedules, there are auto-flowering strains of cannabis, which will automatically go through their whole life in about 3 months no matter what light schedule is provided. For some growers, an auto-flowering strain may be more simple than a traditional (photoperiod) strain.


Most indoor growers provide 18-24 hours of light a day (known as 18-6 or 24-0 light schedules). Giving your cannabis plants more hours of light each day in the flowering stage will encourage faster growth.

Lingo: When a grower provides 18 hours of light a day and 6 hours of darkness, this is commonly known as the 18/6 light schedule. For 24 hours a day, this is referred to as the 24-0 light schedule.


As long as your plant is getting plenty of light a day, your plant will automatically stay in the vegetative stage from late spring until late summer. Every strain is a bit different.

Flowering Stage

Cannabis starts budding when plants get at least 12 hours of uninterrupted darkness each night. After plants start budding, they must continue to get long dark nights until harvest or they may revert back to the vegetative stage.


Indoors most growers put their plants on a 12-12 schedule to initiate flowering. Outdoors the plant will naturally start budding in late summer when nights are growing longer and longer as winter approaches. Just make sure plants aren’t exposed to light during their dark period!

What is 12-12 Lighting?

The indoor grower will need to artificially induce flowering/budding in plants by changing the light schedule so the plant receives only 12 hours of light a day, and 12 hours of uninterrupted darkness.

Once the plant is changed over to the flowering (12/12) light schedule, there is generally another 6 weeks-5 months (average 2.5 months) before the plant’s buds are ready for harvest.


Outdoor growers wait until their cannabis plants start naturally flowering on their own, usually after mid-summer when days start getting shorter than 12 hours.

It’s important to make sure plants aren’t exposed to light at night during their dark period, even street lights or spotlights, as this can prevent cannabis plants from flowering properly.

Learn more about cannabis growing timelines

Growing Indoors? Not Sure When To Switch To Flowering?

So indoor growers have a choice to flower their plants whenever they want… When is the best time to start flowering your cannabis indoors?

The real answer is that it’s a matter of personal preference and also depends on what end result you’re looking for. There are two major considerations when choosing the right time to switch to 12/12, the age of the plant and the height of the plant:

Age: Some growers feel that a marijuana plant which has been grown from seed will not produce as many buds or have enough resin production if the plant is not given at least 60 days in the vegetative stage to mature before it’s changed over to the flowering stage. This is not true. many growers initiate flowering soon after germinating a seed in order to keep plants small and short. This is often called “12-12 from seed.” Just remember, no matter what you do, a young cannabis plant will not start flowering until it is 2-3 weeks old. Even if you put a seed on a 12-12 schedule from the beginning, it will not start properly budding for about 3 weeks. When growing with cannabis clones, age is not an issue and growers can switch directly to flowering once your clone has established roots. This is because even though a clone may be small, it’s still a ‘mature’ plant since it is made of a piece from a mature plant. Rooted clones tend to grow much faster for the first few weeks than plants grown from seed. In any case, age is not much of an issue, and you should switch your light schedule at the time that best fits your needs.

Height: A general rule is that your marijuana plant will double or triple in size during the flowering stage from the point where you first change over the light schedule to 12/12. Some plants will grow more, some will grow less, but a good rule of thumb is to change your light schedule over to flowering when your plants have reached half of their final desired height. Bending, known as “LST” or “low stress training” can be used to control colas that get too tall. Simply bend too-tall colas down and away from the center of the plant. Some growers will even slightly break or “supercrop” branches to get them to bend at a 90 degree angle. For those growing in a small space, height may be the primary concern. However, there are many techniques available to grow a short, bushy weed plant or basically train your cannabis plant to grow into any shape you want.

Here’s an example of LST to keep a plant short:

In optimal conditions if height and space is not an issue, you would probably want to vegetate your cannabis plant for 60 days or more before switching it over to flowering. This gives your plant plenty of time to grow big (so you get bigger yields), and allows new growers to dial in their grow before plants enter the sensitive flowering stage. In the vegetative stage, it is easy to recover from problems, but problems are a lot more serious in the flowering stage, where mistakes can dramatically hurt your final yields.

Giving cannabis plants more time in the vegetative stage, and taking time to train them to fit your space, will give you the best final yields. However, if space is tight, then it’s better to switch when the plant is half the final desired height, or even to just attempt to flower your cannabis plant straight from seed.


After the vegetative and flowering stage are over, it is time to harvest your plants!

When do I harvest my cannabis?

Jump to…

Teach me the basics of growing cannabis

Is my plant a boy or a girl?

How long does it take to grow cannabis?

Plant Problems & Symptoms

Plants And Light: Do Seedling Plants Need Darkness To Grow

Do seedling plants need darkness to grow or is light preferable? In northern climates, seeds often need to be started indoors to ensure a full growing season, but this isn’t only because of warmth. Plants and light have a very close relationship, and sometimes a plant’s growth, and even germination, can only be triggered by extra light.

Do Plants Grow Better in Light or Dark?

This is a question that doesn’t have just one answer. Plants have a quality called photoperiodism, or a reaction to the amount of darkness they experience in a 24-hour period. Because the earth is tilted on its axis, the periods of daylight leading up to the winter solstice (around December 21) get shorter and shorter, and then longer and longer leading up to the summer solstice (around June 21).

Plants can sense this change in light, and in fact, many base their yearly growing schedules around it. Some plants, like poinsettias and Christmas cacti, are short-day plants and will only bloom with long periods of darkness, making them popular as Christmas gifts. Most common garden vegetables and flowers, however, are long-day plants, and will often go dormant in the winter, regardless of how warm they are kept.

Artificial Light vs. Sunlight

If you’re starting your seeds in March or February, the length and intensity of the sunlight is not going to be enough to make your seedlings grow. Even if you keep your house lights on every day, the light will be diffused throughout the room and the lack of intensity will make your seedling plants get leggy.

Instead, buy a couple of grow lights and train them directly over your seedlings. Attach them to a timer set to 12 hours of light per day. The seedlings will thrive, thinking it’s later in the spring. That being said, plants do need some darkness to grow, so make sure the timer also turns the lights off.

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