How to Scrog
SCROG stands for SCReen Of Green.
The idea is to place a screen above your plants and tie everything horizontally to the screen that grows through.
In order to do this you have to top the plants to make sure they get a lot of side branches.
All branches that don’t grow through the screen are pruned off.
This results in a beautiful blanket of main buds.
Scrogging enables you to optimally use your space with only a couple of plants.
This can be useful if you live in a State where you are not allowed to grow more than 5 plants.
The entire grow room needs to be covered with leaves to not waste any light.
Light that doesn’t fall on the leaves and hits the ground is wasted energy.
Indicas grow nice and wide, and not so tall, so 4 or 5 plants per 12 square feet suffice.
But if you want to grow 4 or 5 Sativas on 12 square feet, SCROG is a very useful growing technique.
In this first part I explain how you to scrog, how to install it, and I’ll post the first part of the grow journal.
I’m currently in the flowering phase, so the plants will be ready for harvesting in two months.
I will update this course every month.
Have fun!
How to scrog
Hang a screen or netting about 15 inches above your plants.
Now you have to wait for the plants to grow through the screen.
All shoots that grow about 4 inches through the screen are horizontally tied.
These shoots will grow upwards again, after which we will tie them again.
Eventually you’ll have a full blanket of buds that are all at the same height, so they all get the same amount of light.
You have to top the plants to make sure they get a lot of side shoots.
Do this when they’re about 6 inches tall and have five pair of leaves.
To top a plant, simply cut off the main top, so the underlying side branches grow upwards more.
I’ll show you exactly how to do this in the grow journal.
The grow skills section also contains a great article on this pruning technique.
As soon as the first branches grow through the screen, you put the plants into the flowering stage.
Since they’ll grow for another 2 to 3 weeks in the flowering stage, eventually enough branches will grow through.
Tie everything that grows more than 4 inches through the screen, until the plants are no longer growing. Use plant clips or cable ties for this.
The rest of the growing process remains the same.
Keep the temperature between 68 and 77 degrees and make sure the humidity is around 70% in the beginning and around 40% in the end.
I’ll provide an example of a scrog in this grow journal, but no basic growing techniques, such as lowering the pH and feeding your plants.
If you don’t have much experience with growing marijuana, I advise you to first read the Introduction section.
It’s also smart to first achieve a successful harvest by going through the From Seeds to Bud section.
I’ll now tell you what equipment and setup I use and how to install it.
Then I will post a grow journal with pictures and accompanying text every other day.
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What do you need?
You obviously need a complete grow room with lighting, extraction, reflecting wall and much more.
To find out what requirements a grow room must meet and how to set one up, read courses in the Introduction section about grow rooms.
This is my setup for this harvest.
- 1 x 3×3 foot tent
- 1 x 400 watt MH during vegetative stage
- 1 x 400 watt HPS during flowering stage
- 1 x 440 CFM Air extractor
- 1 x 6″ carbon filter
- 1 x 250 CFM Air inlet
- 4 x 6.5 gallon pot
- 4 x amnesia cuttings
- Flower Power nutrients
In addition to a fully functioning grow room, you’ll need the following for SCROG:
- Screen
- Scissors
- Large pots
The idea of scrogging is to let the plants grow through a screen.
As soon as the branches grow about 4 inches through the screen, we bend them and tie them to the screen.
They will then grow horizontally for a bit and then vertically again.
As soon as the branch grows another 3 to 4 inches, we tie it again.
By applying certain pruning techniques and bending and tying the branches multiple times, we can create a blanket of buds that all grow equally as much above the screen.
Pruning is a very important part of scrogging, so make sure you have sharp scissors.
When you prune a plant you create a wound, so always make sure your scissors are clean and sterile to prevent infections.
If you’re growing on soil it’s important to use large pots, because scrog is especially beneficial for people who can/are allowed to only grow a small number of plants and still want an maximum yield.
By properly pruning them, the plants cover a much larger surface.
If you’re growing on hydro it doesn’t matter how large your pots/slabs are.
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Installing scrog
1. Put your pots in the tent and fill them with soil.
2. Carefully place the plants in the soil and cover them well with soil.
Use cuttings with proper roots or about 4 week old plants from seeds.
3. Water your plants (no nutrients, pH 6.0) and thoroughly spray them.
I now give them about 8.5 ounces of water near the stem of the plant.
Don’t water them too much, because a small plant doesn’t use much water, even though the pot is very big.
If you wet the entire pot, the roots will suffocate and your plants will die.
4. Cut a screen to size and place it about 15 inches above your plants.
Also take into consideration that the lamp has to be able to hang another 15 to 25 inches above your plants, since it would otherwise get too warm.
I have enough room, so I hang the screen at 15 inches.
5. Tie the screen with cable ties, so you still have a bit of wiggle room if needed.
Take a picture of the setup and post it on our forum.
It’s a good idea anyway to take pictures now and then, since problems are easier to diagnose this way.
Our growing experts are very happy if pictures can be provided.
Vegetative stage
Day 1
The cuttings are in the pots, so it’s now important to take good care of them so they can grow nice and wide and create many side branches.
Since the cuttings are used to fluorescent lighting, I’m hanging the lamp all the way at the top of the tent.
In this way they don’t get as much light and they can get used to the stronger MH light.
We’re going to top the plants a number of times and prune a lot.
We top the plants when the plants have about 5 internodes and are 6 inches tall. The plants create more main tops and more side branches if they’re topped.
They also grow wider and less tall.
Since there are only 4 plants in the tent, they have to get quite bushy to make sure no light is lost.
Light that hits the floor and doesn’t hit the leaves is not absorbed and is therefore wasted energy.
If you don’t have much growing experience, I advise you to read the course From seed to Bud.
This grow journal teaches you exactly what the right temperature, humidity, EC and pH values of your plants are.
Day 3
The temperature and humidity are good and the plants look healthy.
They had two days to get used to the strong MH light, and it seems like they ‘took’ well.
I place the lamp a bit closer to the plants, at about 25 inches.
I usually hang the lamp a bit higher when taking pictures, so what you see in the pictures isn’t always correct.
The humidity has to be nice and high in the beginning: around 70% is perfect.
The temperature with the light on has to be between 70 and 77 degrees, and no colder than 60-65 degrees with the light off.
They get a little bit of water, about 3.5 ounces each, again around the stem.
I also spray the plants, walls and floor of the grow tent to create a high humidity in the tent.
The plants will be ready for topping in about two days, to get them nice and wide to eventually cover the entire screen with buds.
Day 5
The plants are looking good, but I decided to wait until after the weekend to top them.
They have to take a bit better and get a bit bigger, because topping requires a lot of energy from a plant. So they have to be a little bit stronger than this.
Other than that, everything is looking good. The temperature and humidity are fine.
The pots are quite heavy, but I’ll water them a bit anyway: 3.5 ounces per plant to survive the weekend. And of course I give them a nice spray.
Day 8
This is looking good. The plants are ready for topping.
This is one of the most important actions to take when scrogging.
By topping the plant, you create multiple main tops to make the plant wider and not as tall.
Topping is very easy.
It’s simply the removal of the main top to make the two underlying side branches grow upwards and become the main tops.
If you do this a couple of times and prune away lower side shoots, you’ll end up with a plant with only main tops and no small side tops.
It’s important to use sterile scissors or a sterile blade and clean hands.
Take the latest shoot between your fingers and cut it off.
Only cut the latest leaf pairs and not an entire cutting.
Do this to all plants and give them some time to recover.
Here’s a photo series of the topping procedure:
Over the next weeks I will record the effect of the topping of the plants, and probably top them again.
Eventually we will prune all branches that don’t grow through the screen and create a large blanket of buds above the screen.
I give them 8.5 ounces of water without nutrients, with a pH of 6.0 and I spray the entire tent.
They won’t get much taller over the next two days, but probably a bit wider. We’ll see…
Day 10
Topping went well, and you can see the plants are getting some more side branches.
It’s now important that they grow towards the screen and get nice and wide.
I will probably top them again in a week to create even more main tops.
I eventually prune all branches that don’t grow through the screen.
They don’t need any water, but I gave them a nice spray with a spray bottle.
Day 12
They’re still doing well and are growing nicely towards the screen.
The pictures below clearly show that the wound healed nicely and that two new shoots are growing upwards.
I give them 17 ounces of water, so they’ll survive over the weekend and I spray everything again.
If you’re growing at home, I recommend that you spray your plants twice a day to keep the humidity high.
Day 15
They’ve grown nicely over the past couple of days and they’re getting quite wide.
Amnesia is a Sativa dominant strain, so they’re fast growers.
I probably don’t have to top them anymore.
I will force the to flower as soon as the plants are touching each other and grow through the screen.
Day 17
Now we have to wait until they’re wide enough to start the flowering stage.
They receive another 17 ounces of water with a bit of nutrients. EC of 0.8 and a pH of 6.
Day 19
I’m not going to top them again, because the plants are wide enough;
you can see various main tops arise that will all grow through the screen.
They receive another 17 ounces of water, because they’re evaporating a lot.
This picture shows that this plant has three main tops that will all grow through the screen.
By tying them, the smaller side shoots will also grow upwards and receive a lot of light.
Day 22
I lowered the screen by 2 inches yesterday, because the plants are wide enough to force them to flower at the end of the week.
They receive 25 ounces of water each, with an EC of 0.8 and a pH of 6.
They’re now almost growing through the screen.
You have to give some branches a little hand to let them grow through.
Day 24
They’re really starting to grow through the screen now.
All water was used, so they’re evaporating a lot.
I give them another 25 ounces each with the same EC and pH values as before.
The branches have to grow a little bit more to bend them.
Once they’re 4 inches above the screen I’ll bend them.
I think this will be the case on Friday.
Day 26
This is looking really great. I’m going to start their flowering phase today.
If the leaves of your plants aren’t touching yet, you can hang the screen a bit higher, so they can become a bit wider.
But in my case they’re wide enough and there’s a nice blanket of leaves.
It’s also time to start bending the first branches.
Pick a 4 inch branch and gently bend it over the screen.
Tie it behind the bending point with a plant clip or a cable tie.
This branch will grow horizontally a bit more and eventually grow upwards again.
Some branches have to be tied two or three times.
During the flowering stage the plants get 12 hours of light and 12 hours of darkness.
As long as they get 18 hours of light and 6 hours of darkness they’ll stay in the vegetative stage.
As soon as the plants are big enough you can force them to flower by giving them 12 hours of light and 12 hours of darkness.
I replace the 400 watt MH lamp with a 400 watt HPS lamp, which is more suitable for flowering.
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They receive 17 ounces of water to survive the weekend and I’m curious to see what they’ll look like on Monday.
The next part of this grow journal will be uploaded a month from now.
I hope you’re inspired to scrog yourself some time.
You can always visit the forum for all your questions and comments.
Flowering week 1 to 4
Day 1
This is looking great! The temperature stays around 75 degrees and the humidity is nice and high.
The soil is pretty dry again, so they’ve evaporated a lot of water.
From now on, they’re getting 42 ounces of water each, every other day.
At the start of the flowering stage I provide plants with an EC of 1.0 and increase it by 0.1 every week.
The pH stays at 6.0.
I again tie down the branches that stick more than 4 inches through the screen.
Make sure they’re all growing in a different direction to ensure they cover the entire screen.
They’ll grow for another two weeks, so it will be a full screen!
Day 3
They continue to grow, so I keep tying them down.
I’ve already tied some of them down twice.
The next time I will prune the bottom that I know won’t reach the screen.
This is because new growth costs a lot of energy, so it’s a waste if the plant has to put effort in creating branches and leaves that won’t ever reach the light anyway.
They’re getting another 42 ounces of water and I give them a nice spray.
Just look how beautifully this branch is growing upwards again.
Day 5
Ahh, what a great field of plants.
The evaporation process continues, because the soil is quite dry again.
I once again tie down the branches that grow more than 4 inches above the screen.
And today I’ll remove most of the shoots that won’t ever grow through the screen.
This new growth takes a lot of energy from the plant and will eventually yield little marijuana.
This energy is therefore wasted.
It’s best to cut off the bottom shoots and leaves with a pair of sharp scissors.
You could also do it with your fingers, which is called pinching.
Take a young side shoot between your thumb and index finger and remove it by pinching your nails together. Always do this close to the stem.
Remove as many young shoots as possible.
You’re going to have to do this several times, because new shoots will continue to form.
This is by the way a good time to preventively treat your plants against pests.
You will have a lot of room to spray them, since you removed all those leaves.
Make sure you especially spray the bottom of the leaves, because this is where spider mites and thrips can be found.
Day 8
Your plants always have to recover for a bit after such a drastic pruning session.
You can see that they haven’t grown much over the weekend.
The cuts from the pinching have healed nicely though, so they’re ready to grow again.
The leaves often discolor a bit, but that’s all part of it.
They’re quite dry again, so they’ll get 42 ounces of water and I increase the EC by 0.1 to 1.1 and keep the pH at 6. Everything else is looking good.
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Day 10
You can see the leaves are glistening a bit.
That’s because of the stuff I sprayed on them.
This is oil extracted from chrysanthemums, which is harmful to spider mites and thrips.
They won’t be bothering us for a while.
Some branches are growing through the screen again so I’m tying them down.
Keep an eye on the height of your lamp.
All tops will now stay at the same height, so you can now determine the ideal distance between plant and lamp.
Calculate 0.1 cm (0.04 inches) per watt.
So this 400 watt lamp will hang at about 40 cm (16 inches).
Day 12
The screen is getting full, and you can see the first little buds appear.
This means I will prune the bottom of the plants one last time today.
I remove all new growth that doesn’t grow through the screen.
I leave the larger leaves on, because they provide energy to the plant.
I’ll give them a lot of water, because the weekend is coming up and I won’t be seeing them until Monday.
They’re getting 68 ounces each.
I’m excited to see what they look like on Monday.
Day 15
This is looking great. The buds are really starting to become nice hard balls with a lot of white little hairs.
The color of those hairs shows when a plant is ready for harvest.
As the plant ages, the hairs slowly become brown or red.
When about 2/3 of these hairs is red, your buds are ready to be harvested.
Full harvest course at this link here.
The plants evaporated a lot of water, so they absorbed a lot of nutrients.
I once again increase the EC by 0.1 to 1.2.
They’re getting 50 ounces of water each. I hope they evaporate all of this.
Day 17
I don’t expect these plants to grow much anymore, so they don’t need to be tied down.
It turned out to be a nice patch with a lot of buds. I think I can get a nice yield from this.
I once again give the plants 50 ounces of water each.
You no longer have to spray the plants once they get their first buds.
You can also slowly lower the humidity.
Day 19
Some leaves are starting to discolor a bit.
This could have to do with the pruning I did, but also with the nutrients.
I’m giving them water without nutrients this time, with a pH of 6.0.
The buds are looking great; very healthy white balls.
From now on I will post more pictures of the buds and fewer of the whole tent.
Day 22
The plants had a great weekend and are looking beautiful.
It’s always nice to see a patch full of buds.
They used a lot of water, so I’m giving them 50 ounces each again.
The EC should be increased to 1.3, but I’m going to keep it at 1.0, because of the discoloration of the leaves.
More and more buds are forming and these little buds will grow towards each other over the next period of time.
Multiple small buds will become a single big bud this way.
They’ll never be huge, because we topped the plants.
Day 24
The development of the buds is still excellent.
They keep growing closer to each other and are almost touching.
All hairs are white and will stay this way for a while.
Here are some pictures of the damage to the leaves.
This looks a bit like root damage, caused by larvae that feed on the roots. But there aren’t any.
The plants had a bit too much nutrients, but this also isn’t the cause of this discoloration.
To be honest, I don’t really know what’s going on.
I don’t really mind it that much, because the plants are still evaporating a lot of water and the buds continue to develop properly.
I will obviously keep an eye on this and the discolored leaves will probably discolor even more.
Day 26
Everything is still quit at the front.
The buds continue to grow and the evaporation process is going well.
It’s right before the weekend, so I’m giving them 85 ounces each, with an EC of 1.3 and a pH of 6.0.
I expect them to have grown quite a bit after the weekend.
The last updates on this course on scrogging will follow in a couple of weeks.
Then I will cover the last weeks of the flowering stage and we’ll chop, cut and dry the plants.
And we’ll of course find out what the yield will be.
