How to grow marijuana from seed

How to grow marijuana from seed

Everything you need to know about growing marijuana from seed

This article is going to look at growing marijuana from seed for medicinal purposes using LED grow lights. We’re going to focus on growing in a small space, six to nine square feet, with three to six plants. We’ll explain plant nutrition in a little more detail in this article as we’ve been getting a lot of questions about that recently. So, here we go. How to grow marijuana from seed at home 🙂

Here are the topics we’ll be covering in this article.

  • What soil to use to grow marijuana
  • Ventilation
  • Growth Stages / Germination
  • Cloning your plants
  • Transplanting your plants
  • LED Grow lights
  • Harvesting your crops

What soil to use to grow marijuana from seed

Try and use a soil that has not been fertilized because we want to fertilise the soil ourselves. The nutrition we will be providing will be perfect for marijuana plants.

You can use standard potting soil that you buy from a garden center. Try and find soil with vermiculite mixed in (or buy separately to mix in). Vermiculite is easy to spot because you’ll notice some little white pieces inside the soil. It’s really good for holding water and keeping air in the soil. You also want a light soil. We’re not growing outdoors, so we don’t have to worry about it drawing up moisture through the soil, because we can control the humidity and the ‘rain’ ourselves.

What fertilisers should we use for growing marijuana from seed?

Fertiliser ratios - Nitrogen, phosphorus, and potassium.

Fertiliser ratios are required for different stages of growth

There’s three different types of fertiliser that you need, one for each stage of growth. These stages are the seeding stage, the vegetation stage, and the budding/flowering stage.

Plants require a certain amount of nutrients called NPKs or nitrogen, phosphorus, and potassium. They’re listed in order on the soil packages as a number. Getting your nutrients right is important, so it’s essential you get this bit right.

Many beginners try to grow marijuana and slip up with the nutrition. Too many nutrients and you can damage the roots. Too little and they won’t grow to their potential. Use the wrong mix of nutrients and we won’t get the maximum yield.

That is fine though because we’ll walk you through what you need now.

The perfect soil for the seedling stage

Plant nutrients for marijuana

Nutrients for growing marijuana

The NPK levels are normally printed on the soil pack. The NPK levels we need for the seedling stage are 20-20-20. Seedlings need a little bit of everything to get started, so just an even amount’s good for that. Just to clarify, its a mix of 20 parts nitrogen, 20 parts phosphorus and 20 parts potassium.

The perfect soil for the vegetation stage

After the seedling stage come the vegetation stage. Marijuana plants in the vegetation stage need 30-10-10 or 20-15-15 because the plant needs a lot more nitrogen to help grow and become big, and then help prepare for the budding stage.

The perfect soil for the budding/flowering stage

flowering female marijuana plant

flowering female marijuana plant

After the vegetation stage comes the budding/flowering stage. Once budding happens and your marijuana plants is getting ready to flower you want to go ahead and move to a 5-20-5 or something with a lot more phosphorous. Marijuana plants will use a lot of phosphorus during the flowering stage so you are best given it what you can to produce as much flowers as possible.

When you grow weed, you want to water your plant about one every few days. You ad add nutrients to this water. Just ensure that you’re watering regularly. You need to make sure the soil’s not dried out, but you don’t want to over water and flood your plants.

Now, in the seedling stage you want to go ahead and fertilise about once a week. Not a lot, but just enough that it can really help it. If you add too many nutrients at this stage you can burn the roots and damage your marijuana plant.

Re-potting your marijuana plants is important

Re-pot your marijuana plants into different pots

Use the 3-1 rule where you water the plant with nutrients three times and then use just water the one time. This is a fairly accurate rule of thumb.

What pot size to use

You will start small and then you will finally go up to a five inch, eight inch, and 12 inch pot. You really want to keep it to a one plant per square foot. It’ll really help you for your grow light calculations later. Just try to imagine 12 inch pot is the largest you want to go.

It’s normally a good idea to put some drainage at the bottom of the pots too in case you over water. This prevents the roots from rotting.

How to ventilate your growing area

Fans when growing marijuana

Fans are useful when growing marijuana

Ventilation is really important when growing weed because you really need a lot of CO2 (carbon dioxide) coming in and hot air being extracted so we can keep the room cool. This is particularly important when you are growing indoors. Sometimes even an open window will work but it all depends on the grow room set-up.

One thing you will need when growing weed indoors is a standard fan. The fan not only replicates natural wind and induces strains steams but it also really healthy for the plants. It blows off dust. You want some good strong limbs. It promotes healthy plant growth. The fans will also help control the humidity and temperature.

Without a fan you’re going to get really hot air in there that’s not blowing around and the temperature’s going to become too hot. It can also help control humidity. If the humidity’s too low you can just put a little bowl of water in the centre of your closet or your grow area and really that will help increase the humidity.

Temperature in your growing area

What is the ideal temperature for growing marijuana? One thing you will need is a simple thermometer. Nothing fancy, just a standard household thermometer will be fine. Keep your temperature anywhere from 70 to 85 degrees Fahrenheit. You definitely do not want to go over 90 degrees. Open windows and air fans can reduce temperatures.

Humidity in your growing area

What humidity do you need when you are growing weed? One thing you will need is a simple hygrometer. Humidity needs to be around 60 to 80%. Don’t get your humidity above 80% because it will promote mold growth and that will just ruin your entire plant.

After you have harvested your marijuana plant, you need to keep humidity down during the drying process because if the humidity is too high and mold grows, your crop will be ruined.

When your marijuana plant has entered the flowering stage and the small flowers have turned brown, you should reduce humidity down to 60%.

If you need to increase humidity, a simple bowl of water in the growing area should work just fine.

Growth stages of a marijuana plant

When you are growing marijuana, it’s important to understand the different grow stages. It’s pretty similar for every plant. They all start at the seed stage, then they grow, then they bud and flower then they die. Well, marijuana is the exact same there. You just need to understand the growth stages, how long these last and what to do with these things.

The seedling stage lasts anywhere from one to three weeks. Your seedling sprout will grow leaves and your plant will grow rapidly. It will eventually start spreading some leaves and they’ll reach the vegetation stage.

The vegetative stage will last three to five weeks. In this stage, the plant is putting all its energy into growing.

The budding/flowering stage finally comes on at seven to eight weeks. This stage means your marijuana plant is almost ready to harvest and will start to get ready to ‘flower’ and then get ready to die.

As your marijuana plants grow and go through the different stages, you will require different size plant pots. During the seedling stage, you are looking at three to five is three to five inches. The vegetation stage is five to eight inches, and budding/flowering stage is eight to 12 inches.

Germinating your marijuana seeds

Our first stage here is germination. It’s when you take the marijuana seed and you germinate them by ‘waking them up’ and getting them to start growing.

There’s three ways of really doing this.

The first way is just putting it directly into the soil, a half inch or whatever down, and just throw it down in there hoping they’ll grow. This is the least effective.

If you use this method, it’s important to ensure you use the best seeds. The best marijuana seeds and most likely to germinate are darker and kind of spotty. Good marijuana seeds look like a tortoise shell. They are dark, spotty and have a ’shell’ like quality about them. You can just drop those directly in the soil and that has anywhere from a 60% to 70% success rate.

The next best way to germinate your marijuana seeds is by taking a paper towel and moistening it. Then place some seeds on that player before placing another moistened paper towel on top of that. This should take about two or three days. That has a 80 to 90% success rate.

The best method has a 90 to 100% success rate. You literally just drop the seeds into a cup of water. You don’t need the water to be distilled or anything. The chlorine will actually help kill the bacteria in the seeds. Drop them in the water and wait anywhere between two to three days. Do not go over two days as you can damage the seeds.

When you first put the marijuana seeds in the water they’ll start floating. After about an hour or so they’ll slowly start dropping down. You can start poking them down with your finger if you like. Leave them for about 24 hours. After 24 hours check the seeds and if you see little orange marks on the seeds, they are good ones for planting. That is the beginning of the seedling.

We are looking for seeds that sink ideally. If any of your seeds aren’t sinking after a 12 hours you can push them down with your finger to see if you can get them to sink. They should always sunk after those 48 hours, but if they’re not and they’re still floating, these seeds are unlikely to germinate.

After about 48 hours, you’ll notice the seeds have the little growth. This is exactly what we want. After about 48 hours, it’s time to plant these seeds.

We are now about to enter the seedling stage.

The seedling stage

After the germination of the seeds follows the seedling stage. Marijuana growers actually class this as the first stage. The germination is a pre-stage. The seedling stage will last one to three weeks. The first leaves to grow will be seedling, rounded leaves and following those you’ll start seeing the jagged-edge marijuana leaves.

The vegetation stage

The vegetation stage follows the seedling stage. This will last anywhere from three to five weeks, but can really last as long as you want. The marijuana plants will be craving blue light during this stage (there is more blue light in the air during the spring and early summer in nature). You’ll be using LED grow lights here and running an 18 hours 6 hours off cycle during the vegetation stage.

Some people will keep their mother plants in the vegetation stage so they can clone them. You clone a marijuana plant (or any plant for that matter) and clipping them and creating more plants with similar characteristics. Every 30 days you can just go ahead and trim up your mother plants, take some clones off, and then you get anywhere from 5 to 15 clones or new plants. If you try to clone during the flowering stage then you can stress the plant too much an damage her.

The flowering stage

After the vegetation stage follows the bud or flowering stage. The stage will last anywhere between 7-8 weeks. Your marijuana plants will be craving red light at the minute from your grow lights. Everything changes and things start budding. You’ll find out the sex of your plant now. The female plants will have small white hairs near the flowers. Once the white hairs start to turn orange, the flower is ready to harvest.

You’ll still be using LED grow lights here and reducing the lights to 12 hours 12 hours off cycle during the vegetation stage.

Male or female plants?

female marijuana plant flowers

female plants have flowers

We are looking for females only – no males. We want to kill any males and keep all the females. The males will have small ‘bulbs’ or ‘buds’ appear near the stems. The females will have small white hairs. It’s important to keep the males away from the females as we do not want the males to pollenate the females. This reduces all the potency of the plants.

You don’t really need seeds anymore since you’ve had your first females. You can clone these female plants.

You don’t want to use males for cloning. Males are really just absolutely useless. Sorry guys…

Cloning your marijuana plant

cloning a marijuana plant

Cloning marijuana is easy

Cloning is a great was to increase your pant yields. You wont have to buy seeds anymore. Cloning is why you really don’t need that male plant. You just take a mother plant, it has to be female (I’ll say it again – it’s that important) and really just cutting it with a razor blade. You’re just going to cut it down on a nice healthy stem, dip it in some rooting powder and plant that directly into a pot.

You really just need to cut it at a 45 degree angle to create the maximum surface area and then cut right down the middle so you have two parts that really stimulate root growth.

A great tip is to stimulate root growth is a rooting hormone. It helps induce the rooting growth, which will have a higher success rate for your clones.

You need to make sure you’re only cutting in the vegetation stage, not the flowering, because it will stress out your plant too much. Because of this I normally take a few cuttings from various plants and make a note of the parent. If the parent turns out to be a male I kill it off. If it turns out to be female – BINGO! It gets easier then as all your plants will be female.

Transplanting your plants

As your pants get bigger and go through the various stages, you will need to start to transplant them. This is pretty easy. It’s just moving one plant from a small container to a large container to help the roots. A general rule of thumb is a one gallon pot usually means about one foot of growth, give or take.

Checking your roots before re-potting

It’s important to keep an eye on your roots so you can re-pot your plants effectively. Roots that are not tangled can draw water better. We need to ensure the plants roots have plenty of room so they can better draw nutrients and water. It is much better to re-pot plants when the roots are in a healthy state rather than leaving it too later and re-potting them when they are a mess.

Having healthy roots is key to having healthy marijuana plants. If your plants roots are healthy, they can take in more water more efficiently, the soil will drain better and they can absorb more nutrients helping them grow bigger and faster.

What grow lights to use for growing marijuana

So, what grow lights should you be using for your marijuana growing project? Well, you need to pay close attention now because this is REALLY important. Out of all the pieces to your growing project, you need to get this right.

The rule of thumb is that great lights make for a great harvest. You can get it wrong on a few things such as temperature, humidity, nutrients but if you get the lighting aspect wrong, your project is doomed.

Incandescent light bulbs

To understand lighting you have to understand the types of grow light you can use. The first off you can use your basic incandescents. They’re the basic lights you get from about 10 years ago. They are cheap but they are expensive to run. They lose a lot of energy in heat so not only do you get excessive heat from your lights but they also cost a fortune to run. These are standard lights designed for humans to see in the dark and are no good for growing plants.

Fluorescent light bulbs

The next type of grow light is fluorescents. You’ve seen these probably in an office building or school. Again, these lights are designed for humans to see in the dark and are not designed to grow plants. They are a bit old fashioned now but they were commonly called ‘energy saving lightbulbs’ or CFLs. They are better than incandescence in the sense that they use less energy but are still not super effective as grow lights. Or, not as effect as other grow lights on the market.

HID grow lights

The best fluorescents grow lights are the HIDs (high intensity discharge). These are in fact designed more to grow plants as oppossed to helping humans see in the dark. They are great at growing weed but again, they are expensive to run and get really hot which will give off tell-tale heat signatures and use a lot of energy.

What’s the difference between fluorescents and the HIDs? Well, it’s lumens. Lumens is really just a measurement of how much power is emitted. Some fluorescent grow lights will emit 60 to 80 lumens per watt. The metal-halides may emit 90 lumens per watt, and the high pressure sodiums (HIDs) may give off 120 lumens per watt. In fact, it’s not lumens we are looking for with grow lights, it’s PAR ratings when we talk about grow lights but we have used lumens purely for an easy to understand example.

LED grow lights

The best type of grow light available right now are LED grow lights. A few years ago, people who grew marijuana pretty much write these off. However, LED grow lights are much more sophisticated now and one of the main benefits of LED grow lights is that they can emit specific light colours. For example, with standard metal halide or HID grow lights, they emit the full range of lights which blend together to form a white / yellow light. Plants do not use all the lights emitted (for example, plants reflect a lot of the green colour which is why they appear green to the human eye).

Another big benefit with LED grow lights is that they use much less energy but still emit a lot of power. This means you can grow marijuana without massive energy consumptions (which won’t alert the every boards to your sudden increase in energy consumption) and that the lights wont create excessive heat which can damage your plants.

here is an article that goes into a bit more depth about choosing LED grow lights.

In the past, some growers would use metal-halide grow lights for the early stages of marijuana growth because they emit a cooler (blue) light which is great the vegetative stage of growth and then HID for the flowering stages as HIDs emit a warmer, red light. This always meant buying two sets of lights and using them at different stages of growth. LED grow lights means you can use one grow light consistently.

The colours of the lights and kelvin ratings

Colour spectrum for plant growth

Marijuana plants mainly use blues and reds in the light spectrum. These are the lights we want.

When we talk about colours of light, we are referring to the Kelvin rating. This is the main difference between that metal-halide and HPS (high-pressure sodium). Metal-halide is your cool white and your HPS is your warm light. Sunlight in the early part of the year June and July, is bright and has a Kelvin rating of 6000k. That’s the type of light we need for your vegetation stage. If you place this type of light on the light spectrum it would be in the blue wave length.

When the autumn comes, the suns light has more red as the sun falls lower in the sky. The light in this stage is about 2,700k. So, this is the light we need for the budding/flowering stage.

Many LED grow lights have a majority of output in the blue and red wavelengths

A long as you have enough power then you’ll be fine. In fact, too much power is better than not enough power.

Grow light timings

Getting your timings right when growing is important. What we can do is start to trigger various stages in the marijuana growth cycle by using timings. It’s a good idea to get a timer which can automatically turn on and off your grow lights. This keeps things nice and constant.

Vegetation stage

For example, when we go through the seedling/vegetation stage, we keep the lights on for 18 hours on and 6 hours off. The 6 hours are important for the plant to rest and recover (just like humans). Its important to keep the light constant. For example, constant light for 18 hours and then constant darkness for 6 hours. Just like you would in nature. This replicates the longer days of spring and early summer.

Flowering stage

When your plants are ready to go to flower you can induce this but reduce the hours to 12 hours on and 12 hours off. You can also fire more red light. This simulates the end of summer. The days are getting shorter. These plants are like, “Whoa. We need to go ahead and bud, we need to go ahead and flower.” That just really helps these plants get huge, dense buds and that warm, warm light that you have will get them really dense. You’re really nailing it to what it would be outside. The closer you can get outside, the better.

Harvesting your crop

Now, we have the best part. You’ve waited all this time, your marijuana buds have finally grown, and it’s time to harvest. Well, when is a time to really harvest? You’ll only have female plants at this point and they will be producing little white hairs. Once these hairs start to turn brown / orange then you’re ready to harvest. The plants at this stage really start to get that characteristic smell too.

A week before you harvest your weed, you need to stop fertilizing. You just want it to go pure water. In two to three days before you’re going to harvest, cut off the water and cut off the humidity to really low humidity, and no water. You want to dehumidify your room and you want to go ahead and start drying out really while it’s still growing, and then you can clip them and go in to hang them.

The low humidity and the low water from when it was growing are going to keep mold away which is what we want. It’s going to take anywhere from two to ten days to 100% dry, and then boom, you’re done. When you’re harvesting you just want to cut off the leaves, separate the buds and hang them, and then when they’re done you can just cut them off.

We’ll create another article on how to process your marijuana plant.

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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