Marijuana (Cannabis)

How To Grow Hydroponic Marijuana

The life cycle of a cannabis plant grown for the marijuana it produces is comprised of germination, seedling, vegetative, flowering stages of life. At the end of flowering the marijuana plant is harvested.

Marijuana Seed That Has Sprouted A Root

To start the growth process, a seed is placed in a warm and humid environment where it begins life. Within a few days the seed will produce a root.

Right after the seed has produced a root, it is supplied with 16-18 hours of light per day. This is called the germination stage.

Marijuana Seed That Has Produced Its First Leaves

The root will continue to expand into the media it is growing in, from the lower portion of the seed.

The upper portion of the seed will develop a stem and its first set of leaves, called cotyledon.

Hydroponic Marijuana Plant Later In Seedling Stage

Once the plant has produced a root and cotyledon leaves, also called seed leaves, it is considered a seedling.

New plant cuttings, also called clones or strikes, that haven't started growing roots are at a stage that is similar to the germination stage of a seed.

Hydroponic Marijuana Clone Entering Vegetative Growth Stage

Once a clone starts to produce roots and new leaf growth, it is in a similar stage of life as is that of a seedling.

When supplied with light, carbon dioxide, nutrients, water, temperatures within the plants tolerance, clones and seedlings develop more leaves and a stronger root system.

Plants should continue receiving the same duration of light they were getting during germination, 16-18 hours of light a day, during the seedling stage of life.

Hydroponic Marijuana Plant In Vegetative Stage

After the plant has put down a solid root system and grown 3-4 sets of leaves, it enters the next stage of the marijuana plant life cycle.

This is called the growth or vegetative phase. During vegetation the light should be on 18-24 hours a day. Longer light periods will result in quicker growth rates.

Hydroponic Marijuana Plant In Late Vegetative StageWhen growing hydroponic marijuana indoors it usually takes about 4 weeks for the plant to go from germination, through seedling, and complete the vegetative stage.

The next stage is called flowering. When growing indoors, the flowering stage is forced to begin by cutting the light down to about 12 hours on and 12 hours off per 24 hour period.

From the time you start to force the plant to flower by switching to the 12/12 light cycle, it will take the plant 10-14 days to start flowering to the point where you can tell by looking at it.

Female Hydroponic Marijuana Plants Flowering

The most commonly cultivated indoor marijuana strains take 7-10 weeks, from when they start flowering to harvest time, when grown hydroponically.

Almost all THC, the primary cannabinoid that causes marijuana intoxication, is produced during the flowering stage. At the end of flowering, marijuana plants are harvested, then allowed to dry.

This is a rough idea of the time frame involved:
--- 4 weeks for germination, seedling, vegetative stages.
--- 2 weeks to flower after beginning 12/12 light cycle.
--- 7-10 weeks from start of flowering to harvest.

Total time from germinating or cloning to harvest time, with one growing area will vary. However, it is generally somewhere between 13-16 weeks with a strain that has a flowering period of 7-10 weeks.

The exact length of time will depend on the particular marijuana strain being grown, as well as the growing conditions. This can be shortened by having two or more growing areas, one or two for the first stages of life and another strictly for flowering.

Where To Grow
Indica And Sativa
Seeds Or Clones
Hydroponic System
Nutrients, pH, Germinating
Male Plants
Harvesting And Drying

Where To Grow Hydroponic Marijuana

This guide is about growing hydroponic marijuana indoors. Where to grow your marijuana depends on what space you have available. An attic, closet, or similar space is ok. But a room, or portion of a room, strictly for growing is preferred.

Things to consider include:
- airflow - has to be good
- water - easy access to water
- well concealed - minimize the chance of theft
- temperature - an area where it is easy to maintain
- electricity - access to enough power to run everything

All grow areas require fresh air from another room or outdoors, or supplemental carbon dioxide to replace carbon dioxide that the plants consume when the grow light is on.

A hydroponic system will require a certain amount of water to operate. It may be easy to transport water to a small system but a larger system might require an amount of water that necessitates a water supply that is close.

A room where the doors can be locked is a good idea for a grow room. That way when the door is locked, a person will have to break the door down to enter the room. This will give you a chance to deter entry.

Heat will probably be the main problem most growers will face because most grow lights will heat the grow area. Maintaining the proper temperature for the plants when the light is on can be a problem.

Hydroponic Marijuana Flowering Under Air Cooled Lighting

A room with an exhaust fan is a good choice, if it is available. Air cooled lighting and air conditioners are other options.

A section of a basement can make a very good area to set up a grow room. There is often a drain pipe that will make cleaning up spills easy.

Basements are often cooler than the house above them, that will help with cooling grow lights. An attic will work, but heat can be a major problem unless well ventilated.

Grow lights and other items necessary to grow hydroponic marijuana will require a certain amount of power to operate.

You will have to take into account the electrical supply you have available to determine what you can run without causing problems.

If the power available in the grow area is limited, you might have to run extensions from other rooms, update the electrical system, get a generator, etcetera to obtain the necessary power.

After you have decided where you are going to grow, you have to clean the area and keep it clean. That means scrubbing walls, cleaning equipment, washing floors, etc. Carpets should be removed, if possible.


This is to minimized chances of the marijuana plants being harmed by biological entities that could have negative consequences.

If you are going to grow in an area where the floor may be damaged by water spills, the area where the hydroponic system is placed should have some kind of floor covering that will protect it.

Once clean, you can paint the walls and ceiling with white paint to reflect light. Commercial reflectors like mylar are best for this purpose because they are more efficient.

Mylar will do the most to ensure a minimum of light energy gets wasted. The closer the mylar (or other reflective surface) is to the plants, the stronger the light that is reflected back on them will be.

Indica And Sativa

Before you can start to grow, you will need marijuana seeds or clones. There are two species of cannabis that are most commonly grown to produce marijuana, they are Cannabis indica and Cannabis sativa.

Even though there are hundreds if not thousands of marijuana strains, most strains grown as marijuana are mainly indica, mainly sativa, or an indica/sativa mix. There are pure indica and pure sativa strains too.

All things considered pure indica, or mainly indica hybrid strains, are by far the best choice for hydroponic marijuana beginners growing indoors.

Mainly Indica Hydroponic Marijuana Plant During Vegetative Stage

They are easier to grow, need less space, require less light, don't get as tall.

The main drawback is marijuana from indica plants generally has lower levels of THC when compared to sativa plants.

For the first few crops, stick with an indica or mainly indica hybrid strain that is relatively easy to grow. As a grower gains experience they may try cultivating a harder to grow strain with more sativa heritage.

Seeds Or Clones

Many people start growing marijuana from seed, but someone who is currently growing a crop might be willing to provide you with clones from female plants.

Marijuana Seed Sprouting On Hydroponic Media

There are benefits and drawbacks to seed. A benefit of seed is genetic variability.

Every seed will have slight genetic differences when compared with other seeds from the same marijuana strain.

A drawback to seed is that unless feminized, there is around a 50% chance that it will be male or female. If you start with 10 seeds, roughly 5 of them will be female.

Since only females are grown to produce marijuana, all male plants will have to be eliminated when the plants flower. In comparison, feminized seeds produce a greater percentage of female plants.

Cutting From Marijuana Plant That Is Being Cloned

Clones are simply cuttings taken from a growing plant. Clones will be exact genetic copies of the plant they are taken from.

A clone will mature like the plant it was taken from, if grown under similar conditions.

Cutting From Marijuana Plant After Excess Leaves Have Been Removed

A major benefit of clones is you will know what sex they are prior to them flowering, since the sex of the clone will be the same as the plant it was taken from.

Seeds and clones will both be capable of producing quality marijuana, if provided with conditions where they can thrive. Some people may develop a preference for either, depending on their circumstances.

Clone Being Inserted Into Hydroponic Media

Make sure to get seeds or clones from a reliable source that can tell you if it is indica or sativa, relative potency, expected yield size, expected flowering time, does it grow indoors or outdoors, and most importantly is it relatively easy to grow.

The flowering time for an indoor marijuana strain is usually stated in weeks or days. It is the period from when you can see the plant start to flower to when it can be harvested.

If you grow hydroponic marijuana from seed, you can clone your plants. Instructions for cloning are located here. You can produce your own seeds by selectively pollinating a limited number of flowers on a female plant, rather than the entire plant, with pollen from a male plant.

Hydroponic System For Growing Marijuana

A hydroponic system is made to grow plants without soil. Plant nutrients are mixed with water and supplied to the plants roots by a pump or other method.

This delivering of nutrients means that the plant doesn't have to expend as much energy making roots in search of the water and nutrients it requires.

Energy saved by not having to look for nutrients and water is able to be utilized to make the plant develop its leaves and flowers faster than they would if grown in soil.

If you are going to be growing hydroponic marijuana and have chosen a suitable location, you will need a hydroponic system, also called a hydroponic garden.

There are different types of hydroponic systems available to marijuana growers. If you would like to know more about hydroponics and the different types of hydroponic systems, there is an article at wikipedia.

There is no one type of hydroponic system that works best for growing hydroponic marijuana. Think about the number of plants you want to grow and the size of the growing container the roots will grow in.

One important relationship between lighting and a hydroponic system is the shape of the reflector that the grow light is housed in, and the shape of the hydroponic garden you choose.

A rectangular reflector will focus the majority of the light energy it produces into a rectangular shaped area.
A square shaped reflector will focus the majority of the light it produces into a square shaped area.
A circular shaped reflector will focus the majority of the light it produces into a circle shaped area.

For this reason, both the light reflector and your hydroponic system should be roughly the same shape. Some hydroponic systems allow the containers the plants are grown in to be moved, this means you can adjust the position of the plants to optimize light availability.

Lighting For Growing Hydroponic Marijuana

Adult marijuana plants do best in strong light. In a perfect world sunlight would be the only source of light needed, but it's not commonly available in sufficient quantity indoors. The next best thing is a grow light.

The most common grow light types for growing hydroponic marijuana are fluorescent, light emitting diode (led), and high intensity discharge (hid) lights like metal halide (mh), high pressure sodium (hps).

Hydroponic Clones Growing Under Fluorescent Light

Fluorescent light is adequate for germinating, seedlings, clones, vegetative stages.

It is not recommended as the primary source of light during flowering because it will produce a small harvest of less potent weed. It will also take more time for the plant to mature.

Hydroponic Marijuana Growing Under Metal Halide

Metal halide can be run during the germinating, seedlings, clones, vegetative stages for faster growth rates, compared to fluorescent lighting.

Metal halide is also good light for flowering. High pressure sodium is usually run strictly for flowering.

The harvest amount reported below is based on experience with mainly indica strains that have some sativa heritage, 60% indica or higher.

Less potent marijuana strains will usually provide a larger harvest amount, when the harvest size is compared to more potent marijuana strains.

The figures are based on flowering under metal halide or high pressure sodium lights. You could get a larger harvest with high yield strains, like big bud.

- A 250 watt mh or hps grow light for flowering will supply enough light to produce about 2-5 ounces of marijuana per harvest.
- A 400 watt mh or hps grow light for flowering will supply enough light to produce about 4-10 ounces of marijuana per harvest.
- A 600 watt mh or hps grow light for flowering will supply enough light to produce about 6-16 ounces of marijuana per harvest.
- A 1000 watt mh or hps grow light for flowering will supply enough light to produce about 10-24 ounces of marijuana per harvest.

Female Hydroponic Marijuana Plants Flowering

Many marijuana growers choose fluorescent light for germination, seedlings, clones, vegetative growth. Then they switch to metal halide or high pressure sodium for flowering.

Sometimes stronger fluorescent or metal halide is introduced at some point during the vegetative stage in order to make the plants more robust and grow faster.

More information about marijuana grow lights can be found here. Be sure to check it out before investing in a grow light or hydroponic system.

Nutrients, pH, Germinating

After you have acquired and installed the items needed to set up your grow room, see the required item list to make sure you have everything, it is time to test everything.

Set up your hydroponic garden, check the light and other accessories to make sure things function properly. If everything looks ok, it's time to add water to your hydroponic system.

With most hydroponic systems, water is mixed with hydroponic nutrients and stored in a reservoir. A pump delivers the water and nutrient mixture, called the nutrient solution, from the reservoir to the plant roots.

When you have the water to fill the reservoir ready, add it but don't add any nutrients. Turn on the pump that circulates nutrient solution and check for leaks.

When you are satisfied there are no leaks, leave the pump running for a while and check to make sure there are no leaks again.

When you are sure that your garden functions properly, you can add hydroponic nutrients to the water in the reservoir.

It is assumed that you are starting with seeds or clones. The amount of nutrient for seeds or clones is very small for the first 1-2 weeks, until you see new roots and leaves forming.

Roots Of A Marijuana Clone Emerging From Hydroponic Media

Until new roots form, some growers add no nutrient to the water supplied to the roots of the plant.

While others, like the author of this grow guide, only add a fraction (1/10th or so) of the amount the nutrient manufacturer recommends for adult plants.

After roots and leaves form, the strength of the nutrient solution is increased gradually. See the page on nutrients and hydroponic marijuana for a more in depth discussion on the subject.

Marijuana plants have an optimal pH level that needs to be maintained. You will have to measure, and if necessary, balance the pH of the nutrient solution.

See the page about pH and hydroponic marijuana here before adding seeds or clones to your garden. When pH is within optimal levels plants will be able to mature as quickly as possible.

Growing Hydroponic Marijuana

This is the time to germinate seeds or introduce clones. Instructions for seed germination are here. With clones, you just have to put them into your hydroponic system according to the hydroponic system manufacturers instructions.

Marijuana Seedling Growing Under 64 Watts Of Fluorescent Light

Hang the light far enough from the tops of the plants so that the heat from the light does not burn the tops of the plants.

As the wattage of the light increases so does the amount of heat it produces. For this reason stronger lights have to be positioned a greater distance from the plants.

Marijuana Clone Starting Vegetative Growth Stage

After a few weeks in the right growing conditions, the germinated seeds or clones will establish a solid root system and produce several sets of leaves.

This is when the plant goes from the seedling stage to the vegetative stage. The plant will grow at a fast rate during veg.

At this point you can either keep supplying fluorescent light, plants grow slower, or you can introduce metal halide light, plants grow quicker.

Marijuana Plant In Vegetative Stage

As the plant grows, some leaves may die. Dead leaves should be removed by cutting them at the stem, rather than pulling them off by hand.

When growing hydroponic marijuana indoors, the germination, seedling, vegetative stages usually take about 4 weeks to complete.

The marijuana plant is allowed to remain and grow in the vegetative stage until it reaches the state where it is ready to flower.

Hydroponic Marijuana Plant Late In Vegetative Stage

To force marijuana plants to flower, the period the light is turned on each day is decreased to 12 hours. For the other 12 hours, the plant remains in darkness.

Flower plants when they:
Are healthy and robust.
Have several sets of leaves.
Have a strong root network.
Are 6 to 12 inches/15 to 30 cm tall.

If they are allowed to grow any taller before flowering is started, there is a good chance they will get too tall, as they continue to grow in the early flowering period.

They won't stop growing for several weeks after flowering has started, so as soon as the plants are ready you should initiate flowering.

Amount of time light should be on:
Germination, clones, seedlings 16-18 hours a day.
Vegetative growth 18-24 hours a day.
Flowering 12 hours a day.

During vegetative growth, you can run the light from 18-24 hours a day. The longer the light is on the faster the plants will grow, plants are healthiest with at least 2 hours of sleep per 24 hour period.

When switching from fluorescent to metal halide or hps light for flowering, do so no later than when you start the 12/12 light cycle to force flowering.

You could start mh or hps for germination, clones, seedlings, vegetative stages. But as was mentioned, don't wait any longer to introduce mh or hps than when the 12/12 light cycle is initiated.

If you are switching from fluorescent or led to metal halide or high pressure sodium lighting, remove the fluorescent or led lighting.

Then install and adjust the height of your metal halide or high pressure sodium grow light reflector hood, where the bulb is placed.

When you first start the metal halide or high pressure sodium, the distance from the top of the plants to the light source should be started at the following height and lowered daily until you find an optimal distance:
--- 18 to 30 inches for a 250 watt light
--- 3 to 4 feet for a 400 watt light
--- 4 to 5 feet for a 600 watt light
--- 5 to 6 feet for a 1000 watt light

Most people recommend starting metal halide light or high pressure sodium closer to the plants but stating at the distances above have worked well for the grower of the plants pictured on this page.

He waits for a day or two after, to see how the plants respond to the increase in light, before moving it closer. You want the plants to be close to the light without being harmed.

If the parts of the plants closest to the light burn and dry out it is a good indication that the light is too close to the plant. Raise the height of the light source.

If the plants are too far from the light they will stretch and get tall. Start high and lower the light daily, until you think the height is right. Don't forget to raise the light as the plants grow, they can grow a few inches in a single day.

Hydroponic Marijuana Flowering

Flowering is the stage of life in a marijuana plant where it produces almost all the THC. Since THC is the primary reason people grow mj, this stage is especially important.

When you are ready to force the plant to flower, after the light turns off, unplug it and don't let it come on the next day. That is, skip 1 day of light and allow the plant to remain in complete darkness. You don't have to do this but it helps the plants start to flower faster.

Hydroponic Marijuana Plants That Started The 12/12 Light Cycle 14 Days Ago

To force the plants to flower, adjust the light timer to turn the light on at the same time it usually does, but only for 12 hours a day.

If the plant got 18-24 hours of light per day prior to flowering, it will flower when the light is on for 12 hours a day.

The height of the plant will continue to increase for a few weeks after the 12/12 light cycle has been started. Strains with more sativa heritage will get taller than strains that are mainly indica.

After several weeks of flowering, the height of the plant will slowly stop increasing and most of the female plant energy will be used for flower production, unless pollinated when some energy will be diverted to produce seeds.

During flowering, the dark period must be perfectly dark. No room light, sun light, or any other light should reach the plant in the hours of darkness that the plant must get everyday.

The strongest light that should reach the plant during the dark period of flowering would equal that of moonlight and only for short periods.


This is more important in the fist 2 weeks after the 12/12 light cycle was begun. When you see the plants have started to flower, small amounts of light for short periods of time during the dark period are not as harmful.

White Hairs (Pistils) Developing At Bud Site Of A Female Marijuana Plant

You will know the plants are flowering when you see what look like white hairs, called pistils, developing at bud sites of female plants or little sacks appearing on the male plants.

Pistils and pollen sacks will start to become visible about 10-14 days after the flowering 12/12 light cycle was initiated. The white hairs turn color as the plant ages. They will eventually be the red, brown, or in some cases yellow hairs that you see on marijuana buds.

Male Marijuana Plants

Sinsemilla marijuana is a term for female plants that have not produced seeds. Not producing seeds allows the plant to devote more of its energy during flowering to producing THC.

Sinsemilla is the result of removing male plants from the grow environment before they have a chance to fertilize the females.

Male Hydroponic Marijuana Plant Flowering

People who grow marijuana indoors or with a greenhouse always grow sinsemilla. Growing sinsemilla outdoors is harder.

Outdoors, a single male plant can fertilize females within an area of a few hundred feet, or even further depending on the wind.

Indoors, a single male plant will fertilize all females plants in the grow room. Which will result in thousands of marijuana seeds, and lower potency marijuana.

If you have started from clones you can skip this part as the clones you obtained were female but if you have grown from seed, you will have to separate the male plants from the female plants before the male plants flower and produce pollen, unless you wish to produce seeds.

Pollen Sacks On A Flowering Male Hydroponic Marijuana Plant

Unless feminized, there is approximately a 50% chance a seed will be either male or female.

Assuming all the seeds are of the same strain, the male plants will generally mature before, or at the same time as the females.

The male plant will have small oval pollen sacks that the female lacks. Once you see these sacks, remove the male plants from your garden. In contrast, white hairs (pistils) will begin to develop at bud sites of female plants.

Harvesting And Drying

With most marijuana strains grown indoors, about 7-10 weeks after a plant has shown the first signs of flowering it will be time to harvest. It is important to harvest at the right time.

Harvest too early and the marijuana will not be very potent and the amount produced will be minimal. Wait too long and the harvest size increases but the potency suffers.

The optimal time for most growers to harvest marijuana plants is just after THC production has reached its maximum, and is starting to slow down.

Hydroponic Marijuana Plants That Are Ready To Harvest

A rough guide as to when to harvest is to wait until 50%-80% of the white pistils (hairs) have turned dark, usually brown or red.

Other clues that a plant is ready to harvest include: a stronger aroma than usual from the plant, a frosted appearence around the buds, and calyxes (seed pods) swelling.

But a better method of determining when to harvest is to wait until certain trichomes on the plant have matured. There are trichomes on marijuana plants that develop a round head on the top.

Capitate Trichome On Marijuana Plant

They are a rich source of THC and other cannabinoids, and monitoring them will help you judge when the plants are ready for harvesting.

A more detailed description of harvesting directions can be located here.

After the plants have been harvested, large leaves should be cut off, buds should be cut from branches and manicured, bud trim and buds are cured and dried.

You Can Harvest A Marijuana Plant One Branch At A Time

Marijuana is not at peak potency just after harvest, it can also be harsh and bad tasting.

Curing and drying will make certain that the potency and taste are most favorable. After the plants are cut down, most of the thc is in a non-psychoactive acidic form.

Besides improving the taste, curing and drying marijuana will convert some of the non-psychoactive acidic compounds into psychoactive thc. Instructions for cutting off leaves, manicuring, curing, drying are here.

Marijuana Bud After Being Manicured

If your marijuana is going to be stored for any amount of time, it should be put in an air tight container and be stored somewhere that is dark, dry, and cool.

Remember that light, air, and heat are the things to avoid. They will degrade THC and make marijuana less potent.

Required and optional items list is here.
Intermediate marijuana hydroponics is here.
Growing hydroponic marijuana index is here.

Related Books

Grow Great Marijuana
Grow Great Marijuana

The Cannabis Encyclopedia

The Cannabis Encyclopedia