How to grow weed

LED grow lights for growing weed

How to grow weed

Introducing: How to grow weed in your home quickly and easily using LED grow lights

Growing weed* for medicinal purposes is becoming more popular. Growing marijuana in your home is becoming much more affordable and easier thanks to advances in technology and especially with the introduction of LED grow lights. In this brief guide, we are going to cover the basics so you can start to grow your own marijuana at a fraction of the cost easily and quickly.

* We will be using the term marijuana for simplicity but we also mean cannabis, marijuana, mary jane, pot, grass, dope, ganga, herb or whatever you may call it)

How to grow weed: Choosing a grow area

how to grow weed - grow area

How to grow weed in your home

With the right care and attention and a little bit of knowledge, you can grow weed in a simple indoor environment safely and easily. You can grow anywhere in your home thanks to LED grow lights and simple, easy to obtain growing materials.

Let’s take a look at a very basic setup and some important features that we’ll be working with in order to get a great yield of weed for personal medicinal use.

How to grow weed: Keep your growing area clean and bright

It’s important when growing weed to keep the plants healthy and free of disease. So, wherever you decide to grow, ensure the whole area has been vacuumed and cleaned with a household disinfectant. Once it’s clean we’ll need to keep it that way.

Also, to maximise the effectiveness of your LED grow lights, which will provide the light for your weed, it’s important to reflect as much of that light as possible back into the growing area. The reflected light is not as efficient as direct light but is better than completely losing it. To reflect the light, you can either paint the walls white or use silver foil or even a grow tent. When you grow weed indoors, it’s important to keep a consistent temperature so make sure your growing area is set up from the beginning.

How to grow weed: What is the best temperature?

Growing weed is easy as long as you get the basics right. One of the keys to success is a consistent temperature. For that reason, we recommend a basic thermometer. We will be aiming to keep a temperature of between 20 and 25 degrees Celsius.

Sometimes, you may wish to include a fan in your growing area which can distribute the heat a little and also replicate natural wind which can help your weed plants grow stronger. Keep in mind that fans may change the base temperature of your grow area.

How to grow weed: What grow lights are best?

We recommend LED grow lights for growing weed in the home. LED grow lights consume electricity (so no suspicious peaks in electricity usage), provide the perfect light required for growing weed and you don’t get the heat signatures that can cause damage to plants or alert authorities to your activities.

One of our recommendations for LED grow lights is that you buy the highest quality ones available. When you buy cheap LED grow lights, the drivers can be poor quality which results in low power output and failure. Buying cheap LED grow lights is often a false economy that home growers quickly regret. You will also require adjustable hanging mechanisms so you can easily raise and lower the LED grow lights as required.

At some point in your growing project you will require a timing mechanism because during the first growing stages you will have the lights on for 18 hours a day and when you want your weed plants to flower you will reduce this to 12 hours a day. Again consistency is required so you need an automatic timing mechanism.

When you grow weed indoors, there is always the inherent danger of water and electricity coming into contact. We obviously recommend that you keep all electrical power points away from water as much as possible. This is another reason why we recommend LED grow lights as they are less susceptible to water. One thing to check is the IP rating of your bulb. An IP rating of IP5X or IP6X is ideal.

In summary, you want;

  • An LED grow light that emits blue/red light
  • An LED grow light with a timing mechanism
  • An LED grow light with adjustable height mechanism
  • An LED grow light with good drivers (not cheap)

Beginners guide to growing indoor plants using LED grow lights

How to grow weed: What’s the best humidity?

How to Grow Weed - Regulate Temp / Humidity

Regulate the temp and humidity

Humidity is another consideration to take into account when growing weed in a confined space. We use a simple hygrometer, which will tell us how humid our growing space is. Throughout our project, we’ll be working between 50% to 80% relative humidity.

When the air is too dry, it’ll affect the growth of our plants and promote unwanted insects and pests. If it’s too wet, we could get fungus, which in turn can rot the buds (which is the bits of the marijuana plant we really want to harvest).

We’ll be able to help regulate the humidity of the growing area with a simple fan and air extractor. Our fan will cool the light, circulate the air and even stimulate nature’s breeze to promote a strong, healthy marijuana plant. You can use an air extraction unit to extract stale air, a window that could be open on a semi-regular basis would work just as well. One thing to bear in mind is that your marijuana plants may give off a strong smell when they start to flower.

How to grow weed: How much to water your plants

OK, so now we have our clean grow area, LED grow lights, thermometer, hygrometer and are now ready to start to grow our weed. Is there anything else we need to consider?

how to grow weed - using rainwater

Marijuana likes natural rainwater

Another important thing to consider to grow healthy weed plants is the water you give them. Because marijuana grows at such a fast rate, our plants will need lots of water by the time they mature, but too much or too little water can make the difference between a perfect crop or just plain disaster. As a general rule of thumb, you are best under watering your weed plants as its easier to revive an under watered marijuana plant than one that has rotted roots from too much water.

Ideally, our water should have a pH value of somewhere between 6.3 and 6.9. A pH scale reads from zero to 14. So, we want to fall almost in the centre. At 7.0, it is neutral, and the closer it gets to zero, the more acidic it will be.

On the other side of neutral, as it moves towards 14, it will become more alkaline. So we’re aiming for water that is slightly on the acidic side.

Most rain waters will have the desired pH or come very close. Rain water is popular mainly because it’s natural and it is free. However, when rainwater is in short supply, tap water is okay to use. We can measure this by using a simple pH litmus strip and we can adjust our water by adding a pH solution.

Rainwater is the most suitable for growing weed but if that is hard to source, you can use tap water. Tap water is usually alkaline, and we can bring it down by adding one of the two pH minus solutions. The first is a diluted nitric acid and is used for when the plant is in the growth cycle. That is when it’s getting 18 to 24 hours of light a day. The second is a diluted phosphoric acid, which we’re using for the flower cycle when the plant is getting 12 hours of light a day.

Our tap water is a little on the alkaline side, and we can bring it down to slightly below seven by adding some pH minus (you can normally get this from pet shops for home aquariums).

Growing weed indoors: What is the best soil to use to grow weed?

how to grow weed - soil

Soil feeds your marijuana plants

Soil is pretty easy to get right. The ultimate soil would be homemade organic compost but it is quicker and easier just to buy in the right type of soil. The human body need quality food and nutrients to thrive as does marijuana. In order for the marijuana plant to develop and grow to its full potential, we’ll need to choose a well balanced soil mixture, one that will provide good drainage and anchorage for the roots and allow the plant to receive it’s water, air and food.

Think of the soil as food. To get the best crop yield from your weed plants, use the best mediums possible.

We will be looking at potting soil, building sand and a little perlite as a minimum. When growing weed, we want good drainage and aeration for the roots so we will blend our potting soil with other materials.

The ideal soil mix for growing weed is;

  • 60% quality, potting soil (we want sterlised soil with no undecayed matter)
  • 15% perlite which will help aerate the soil and aid drainage
  • 10% building sand to help drainage (not beach sand which will contain harmful salt)
  • 10% worm castings which is an excellent food source and a real natural fertiliser.
  • 5% premix which contains some very important nutrients for keeping our plants healthy as they grow. We are looking for a high nitrogen content here

If you cannot get all of the above, then an 80% soil and 20% perlite mix will be satisfactory.

It’s important to not overfeed with premix. Giving too many nutrients can result in burning the roots. Once you damage the roots it’s game over.

The final mix should result in a soil that is moist, but not sticky. It should also stay fairly loose when wet. When you give it a squeeze, it should break up fairly easily. Our roots should have no problem getting through the soil. You should be able to use any quality potting soil from a garden centre. Bear in mind that Marijuana plants like a soil that is slightly on the acidic side.

Growing weed indoors: How to germinate your marijuana seeds

how to grow weed / germination

Germinating marijuana seeds is easy

Now we have the correct soil to grow weed, we are ready to germinate the marijuana seeds. At this point, we can be selective and choose seeds, which have a good brown or grey colour. The pale green coloured seeds will have little chance of germinating. So, we’ll simply discard them.

NOTE: We are only looking for female marijuana plants

It’s important to remember that we only really want the female marijuana plants and we cannot tell which ones are male marijuana and which ones are female marijuana plants until the end growing phases. The seeds on average will be 50% male and 50% female. So, always have in the back of your mind that of the seeds that will germinate, you will probably discard 50% down the line.

How to grow weed from seed – related article on growing marijuana from seed

Germinating marijuana seeds

Method one:
Using our rainwater, first, we’ll moisten some tissue paper / kitchen roll, place our seeds on top, fold over and add some more rainwater and insert into a plastic bag. Finally, sealing with a little sticky tape to prevent any moisture from escaping and place on our windowsill for two to three days. After about three days, our seeds will have sprouted.

Method two:

germinating marijuana seeds

Germinating marijuana seeds using paper towels

Get a small plate and place your tissue paper / kitchen roll on top. Moisten this kitchen roll and place the marijuana seeds on top and then fold over the kitchen roll and moisten again. Look at making the paper damp but not soaking. Then, place another similarly sized plate on top and leave for a few days. After about three days, our seeds will have sprouted.

Once your marijuana seeds have sprouted, it’s time to pop them into their first pot. The goal of this stage is to establish some strong roots. Your first pot should be about 10 centimeters deep.

Planting your marijuana seeds

Make a small hole about two centimetres deep and place the marijuana sprout root down five millimetres below the surface. Cover lightly with soil and water lightly. At this point in the project, it’s important to keep the surface moist until our sprouts have come through.

This grow cycle will take about two to three weeks. Our aim is to get some roots and small tiny leaves on our marijuana plant. We will need to give, our marijuana seedlings constant light throughout this period. We just need to ensure that the soil does not dry out too much.

After only a couple days in soil, the first signs of life appear. After one week, the progress is quite rapid as the marijuana plants are trying to compete for light. It’s important to keep the surface of the soil moist, but not saturated. Too much water can damage the roots at this stage.

In approximately two weeks and the root system is well developed, and we’re ready to transfer our marijuana seedlings into larger pots, using our original soil mix. At this point in time, something important is going to happen. We’re now going to use our LED grow lights to accelerate the growth pattern.

Growing weed indoors: Using LED grow lights to accelerate growth in the early stages

In the early stages of growing weed, we are looking to promote big growth with strong healthy stems. The marijuana plants will be craving blue light at this point as it replicates what they get in nature (blue light is more prevalent in the early seasons). If you are using a fan, this will replicate natural wind and this promotes marijuana plants in the wild to resist by growing stronger stems and leaves. At this stage, we will be using the LED grow lights for 18 hours per day with 6 hours darkness. This allows the plant to get some rest from growing. It is wise to use a timer here so you can regulate the amount of light your plants get and stay consistent.

During this stage (called the vegetative stage) your marijuana plants will require about 3.5 weeks of light and enough water to keep the soil damp but never bone-dry or saturated.

Keep your eye on the temperature and the humidity.

After about 3.5 / 4 weeks we will want to start the flowering stage. When growing weed indoors with LED grow lights, it’s crucial that you do not grow too much during this first stage and let your plants grow too tall.

Growing weed indoors: Using LED grow lights to start the flowering phase

A female cannabis plant starting to flower

A female cannabis plant starting to flower

Once your marijuana plants have been under the grow lights for about 4 weeks, they should be nice and healthy looking and ready to flower. It is the flowering stage we are most interested in when growing weed as this is when we are looking to yield our crop.

Just as in nature when the days become shorter, we do the same with our lights. We swap the 18 hours on / 6 hours off to a 12 hours on / 12 hours off. If possible, we also let our marijuana plants receive as much red light from our LED grow lights as possible (replicating the more red light in the end of summer in nature).

Our LED grow light will be approximately 1 metre above the plants. We’ll maintain the temperature at around 20 to 25 degrees Celsius and the humidity at 60%.

Water your plants every two or three days and we may need to increase nutrients during this stage. Your marijuana plants will be craving nitrogen at this stage. If any of your marijuana leaves are a lime green/yellow, then you will need more nutrients.

A great way to keep a track on how much water your marijuana plants need is to place a finger down into the soil (take care not to damage any roots). We can now feel if the soil on average is moist or dry. When it is dry, we can slowly saturate the soil with water until it runs out the bottom of the pot. Check back in a couple of days, and when the soil is dry again, repeat the process.

The main idea is not to overwater, which can kill a plant’s root system. Once yoru marijuana plants root are runed, it’s game over. By keeping track of what’s going on, we soon learn how much and how often we have to water in our growing environment.

Growing weed indoors: finding out the sex of your marijuana plants

All marijuana plants may look the same, but in reality, probably half are male marijuana plants and half female marijuana plants. We are only after the female marijuana plants and will discard the male marijuana plants.

It is the female marijuana plants that will create the flowers that we will use. Male marijuana plants have pollen sacks on the ends of the branches and where the branches come off the main stalk. They look like bunches of tiny green seeds. If we let a male marijuana plant to keep flowering like this, it will develop to this stage of maturity. The pollen sacks will open and release pollen, which will fertilise the female marijuana plants. We do not want this. So at the first signs of pollen sacks, we’ll carefully dispose of any male plants. This is crucial!

Female marijuana plants look much different when they flower. At the ends of the branches and where the branches come off the main stem, there are little white hairs, which will develop into a female flower. We can determine that this is a female marijuana plant, because instead of male pollen sacks, which look like little tiny balls, the female has very small white hairs coming out of it’s nodes. By removing the male marijuana plants before they release their pollen, the females flowers will grow more and more white hairs, and the top will develop into a sensimilla flower top. That’s what growing strong marijuana is all about. That is why we grow weed!

Growing weed indoors: feeding your marijuana plants

From here in, our marijuana plants will require liquid nutrients to supplement the nutrients in the soil which will be running low. You can use liquid food but it must be diluted otherwise it can kill the plant. Most fertilisers will work including tomato fertilisers but specific marijuana liquid plant food is best.

You can start to give you marijuana plants fertilizer from two weeks in. Its is essential that you give fertiliser during the flowering stage. When growing weed, you can use the 3-to-1 rule. So, you give nutrient rich water 3 times and then just water once. Then, rinse and repeat. We will put matches in the soil every time we water the plants with nutrients so we can keep a record of when we need nutrient water and when we need just water.

You can get a indication of the health of your marijuana plants by the colour of the leaves, They should be a deep green colour. If they are a lime colour or slightly yellow, then your marijuana plant will require more nutrients.
We do not want the marijuana plants to grow too tall at this point and want the energy going into the flowering stage. We normally lower the LED grow lights at this stage to take them closer to the plants. We sometimes will reduce to as close as 50 centimeters.

Growing weed indoors: the flowering stage and increasing potency

A mature cannabis plant ready to harvest

A mature cannabis plant ready to harvest

After a further two weeks, the first signs of buds may begin to show. We want to ensure that the buds do not become too moist. We need to reduce the humidity to around 50% to 60% by increasing the ventilation.

We want to increase the yield on the plant now and allow the marijuana plant to concentrate on putting it’s energy into creating THC (the active ingredient in marijuana) and the flowers. We can achieve this by pruning back some of the lower branches.

A further three weeks, and you may need to add support to the plants. The marijuana plant is likely getting quite big now and we don’t want it collapsing under its own weight. As the marijuana plant grows, some of the larger leaves may turn brown. Simply pull them off. This is natural. The hairs on the buds may turn brown, and this is the sign that they are reaching maturity. This is a sign that we are almost ready to harvest.

Growing weed indoors: Harvesting your marijuana plant

Once we have reached this stage, we’ll stop feeding, watering and spraying. After a further five days, we can harvest our crop.

NOTE: when growing weed it’s important to know what type of high you’re looking for. The longer you leave the harvesting after they ripe th eheavier, and sleepier the high. Early harvests tend to give a more activated high.

On average, the flower cycle can take between 8 to 12 weeks depending on variety. It’s best not to rush the flowering stage as the marijuana plants are creating all that THC which is what gives the weed it’s potency.

We harvest the weed by removing all the big leaves and gradually work our way down to the buds. Any leaves should be discarded. Any leaves with a sticky residue should be kept and put aside. Any flowers and buds should also be kept and put aside separately.

The fine cuttings around the buds can be dried and placed in a plastic bag and stored in the freezer. These can be used to make hashish.

We’re finished with trimming when only buds remain. We’ll need to hang our buds somewhere in a dark, draught free place and keep them at around room temperature. We normally use a storage cupboard. Somewhere dark, dry and enclosed.

You can expect a weight loss of around 70% to 80% (which is mainly water), which can make the environment quite humid. Any draughts or drop in temperature can introduce fungus, which in turn could rot the buds.
After about five to eight days, our buds are dry, and we can cut them off their stems. Once we’ve bagged

them, we can simply squeeze out the excess air and seal and store in a cool dark place. For longer-term storage, we can use a vacuum machine and store the buds in a freezer.

If you have reached this stage then congratulations on successfully growing weed indoors. Your biggest financial outlay (LED grow lights) can be used time and time again and can provide a great return on investment.

About the Author

I first got into LED grow lights when a close friend started suffering from multiple sclerosis and needed medicinal solutions to help manage their condition.

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