When To Re-Pot Your Cannabis Plant And Why
The size of a cannabis plant will depend on the size of the pot it is grown in. Cannabis seeds grown in small pots will become small plants and large pots will encourage larger plants. Many growers choose to start their plants off in small pots and move them into larger ones later on.
Repotting plants like this has many benefits for the root ball and general development of a cannabis plant. That said, knowing the best time to transplant can make all the difference if you’re looking to grow a high yielding plant with a robust root ball. To grow the best medical marijuana everything must be taken into consideration, not just the parts of the cannabis plant you can see.
You can get away without repotting as well, but you’ll get better results if you re-pot them into something smaller first!
How Do Cannabis Plant Roots Grow?
A cannabis seed generally starts under ground in complete darkness, its root system will naturally grow into this darkness and start to fan out while growing down. If a root encounters any light or air as it grows, it will “air prune” itself and branch off into different direction. This process is a natural, healthy way to keep the roots in the dark and helps them in their search for nutrients. Air pruning will make the root ball denser as it happens more and more. Ultimately, the root ball will hit the bottom of the pot and start to spiral along the side of the pot.
Air pruning is a process that causes roots to multiply when they come into contact with air. Fabric pots like the one in this picture stimulate air pruning because the roots get more air.
The first root that comes out of a cannabis seed is the tap root, which extends downwards and anchors the cannabis plant into the medium. This helps create the support a cannabis plant needs to grow upwards. The tap root will also be the base from which many smaller roots grow.
The smaller roots that grow from the tap root are called fibrous roots and their job is to search for nutrients and water. Most air pruning occurs in these roots, making them more efficient in their search for nutrients and water. In the same way that you can pinch out or top a cannabis plant, you can make the root zone much denser using only air.
Why Do I Need To Transplant My Cannabis Plant?
As mentioned above, the roots of a cannabis plant will dig themselves down and push through the dark, moist medium searching for nutrients. This way the roots grow into the shape of the pot and eventually become root bound. Plant roots will always end up growing in the same shape as the pot. So whether you’re using a round pot or a square pot, the root zone will still grow to this shape. The only way to prevent root bound and struggling plants, is to transplant them once you are happy with the root ball. Ideally, the root zone is compact but not too dense to breathe.
This picture is a good example of a full, dense root ball. By filling out a root ball this densely you stimulate maximum nutrient absorption and optimal yields! Can you guess which shape the pot was?
A good example is to take a healthy, well rooted cannabis plant grown in a 5 litre pot and to transplant it to a 15 litre pot. Over time the cannabis plant will expand the root zone in every direction to find new nutrients and minerals and fill out its new pot. Starting cannabis seeds off in a 15 litre pot directly may not be as rewarding as it will not stimulate the root ball to become as dense. Another benefit of transplanting is that you actively break the roots apart, encouraging new root growth in every direction.
Re-potting a cannabis plant helps build a dense root ball that uses the entire pot. Without repotting the roots will shoot down and make less efficient use of the medium.
Is A Root Bound Cannabis Plant Always Unhealthy?
When growing medical marijuana from your own home or commercially, there are serious downsides to letting a cannabis plant become root bound. The most important negative effects include small stunted plants, root rot, slow nutrient uptake, under watered plants and low levels of production.
A cannabis plant can remain relatively healthy while being root bound, but will definitely suffer in terms of production. Healthy root bound plants will stop growing at a certain point as they simply can’t make more roots, this also causes water to be used up very rapidly. Using a certain size of pot can be a practical way to keep your cannabis plant at a desired size, but does increase your chances at running into problems.
This Fast Bud Outdoor plant was grown indoor in a 2 liter pot. You can “break all the rules” as long as you know what you’re doing, whether this is the most efficient or practical is a different story though.
If a root zone is so compact that it cannot breathe, it creates the perfect conditions for root rot. This condition causes cannabis plant roots to go from a bright hairy white to a yellowing brown. Root rot is difficult to fix and can easily kill an affected cannabis plant in only a few days. The root zone is the heart of a cannabis plant so an unhealthy root zone will lead to a sick plant and can easily kill freshly germinated cannabis seeds.
If you discover that you are suffering from root rot and see browning of the roots, you can salvage your grow if you get to it in time. You can use hydrogen peroxide to kill the bacteria that have been building up living in your medium thanks to the limited oxygen. After this, make sure your medium dries up properly so that the roots get air. Ensuring your root zone has good aeration and room to breathe will ensure that your cannabis plant stays happy and pathogen free. Root rot is usually caused by overwatering, but if the root ball has truly become too dense to breathe, your cannabis plant definitely needs a bigger pot.
The roots in this picture are not doing well, the brown color is a clear indication of root rot!
When To Re Pot Your Cannabis Plant
Most cannabis growers transplant their crop two or three times before starting the flowering phase. Ideally, a cannabis plant should be transplanted to a pot that is around 3-5 times the size of the previous container. Smaller will have you repotting too often, larger will make the root system much less dense.
The first pot on the left can contain up to 7.5 liters, the one next to it can hold 12L. Transplanting between these two pots would not add enough room to make it worthwhile.
Generally you will want to allow a cannabis plant to grow for around 3 weeks per transplant. The most common moments to transplant are after the seedling stage, during early veg and again a few weeks before flowering. The exact timings and the number of transplantations depend on the duration of the vegetative phase, medium, training and strain. The global instructions in this article will therefore work for virtually every grow, but can obviously be optimized once you’re more familiar with your setup.
You will have to decide the size of their final pot, as well as what medium you will grow in depending on the total amount of medical marijuana you need. Make sure you repot your cannabis plant shortly before switching it to flowering. The reason for this is because you should avoid shocking a cannabis plant during flowering at all costs. Repotting a cannabis plant during flowering will stunt it and can be very detrimental to your harvest. Just like the rest of the cannabis plant, the root zone will be grown and shaped mostly during the vegetative stage.
Most growers like to start their seeds in a coco, peat or rockwool plug, these provide enough room for root development for the first week or two. After the first leaves come out your seedlings will need some more room and food, so it’s time for their first transplant. The first pot is usually smaller then 1 liter in size, some growers like to go as small as 200mL. Let’s say we’re aiming for a 10 liter pot to finish flowering in, in this scenario a 500 mL would be good to start with.
These seedlings have developed their first leaves and are in the process of being transplanted. A 500mL pot filled with hydroton will provide enough room to grow for the next few weeks.
Two to three weeks after its first transplant, your cannabis plant is ready for its second transplant. This is the time it usually takes to develop three or four sets of leaves and the moment its first full sized leaves start to appear. Without transplanting, a young cannabis plant will become root bound and stop growing at some point after these first big leaves are developed. You can tell this is about to happen when you see a sudden burst of growth and the stem becomes thick enough to hold onto gently without snapping it. At this stage, where a seedling has truly become a small plant, it is time for the second re-potting. The second pot should be quite a bit bigger than the first one and should be large enough to last for most of the vegetative stage. A good fit for our root bound plant in the 500mL plastic cup would be at least a 2 liter pot, let’s say we’re using a 2.5 liter pot in this example.
These cannabis plants have developed a few nodes, and have just started making full-sized, 5-fingered leaves. Now that these stocky little ladies have moved past the seedling stage and grown a bit, they’re ready for their next pot.
Before actually completing the vegetative stage, it is time for the third transplant. For many growers, as well as in this example, this will be the final pot in which flowering stage is completed. By moving our cannabis plant from a 2.5 liter to a 10 liter pot, we’ll add plenty of space to grow roots during late veg and early flowering. We like to start flowering two weeks after the final transplant to make sure the cannabis plant will have completely adjusted to its new surroundings. A cannabis plant that has been grown, pruned and transplanted correctly during the vegetative stage will pay off during flowering and yield an enormous amount of medical marijuana.
After a few weeks of vegetative growth these ladies are ready for their final pot. With multiple nodes worth of full sized leaves, you can tell these are mature cannabis plants that are ready to flower
The sizes mentioned here are all based on our preferences and work well for soil and soilless media like coconut coir. The best sizes for you and your setup might be very different, so experiment as much as you can to see what works best for your grows. Make it your goal to be able to feed every 2-3 days throughout the grow without overwatering. If your cannabis plant is in an appropriately sized pot, it will be able to draw all the moisture out of the medium in a few days.
The Final Pot Size
Many medical marijuana growers are under the impression that the roots of a cannabis plant will fill out its pot during flowering. This is true, but the root zone will grow the most in the vegetative state so this is the time to shape them properly. If you want a cannabis plant with an optimal root system during flowering, you have to start by growing dense roots throughout the vegetative phase. Choosing the final pot size should be based on the roots having enough room to settle and then focus on feeding during the blooming phase.
These monster plants were vegged for over 4 months and have packed on more than a pound each during flower. This wouldn’t have been possible without multiple transplants and an enormous final pot.
The final transplant should take place 2 weeks before flowering your cannabis plant. This will allow time for the root zone to expand without becoming root bound for the rest of the cannabis plant life cycle. When flowering is induced, the root zone will continue to grow for the first 3-5 weeks, after which most of its energy will be geared towards developing heavy flower sets of medical marijuana.
We hope this article has been helpful and has increased your toolset for cannabis cultivation. We also hope to have given you some new ideas on how you can grow the best medical marijuana for your personal needs. As always, good luck growing and have fun with your cannabis plant!
Repotting a cannabis plant has many benefits for the root ball and general development. Knowing the best time to transplant can make all the difference.
When Do I Transplant Cannabis Plants?
Why Should I Transplant My Cannabis Plants?
There are advantages to transplanting your marijuana, and this transplant guide and tutorial will teach you when and how to transplant your pot plants perfectly every time. But why should growers transplant their weed plants in the first place? Why not just plant them in their final container from the beginning? The reason is that a proper transplanting regimen actually makes your plants grow faster in the vegetative stage!
Transplanting Young Cannabis Plants At The Right Time Makes Them Grow Faster!
If you start your cannabis plants in a relatively small container they will grow faster than if you planted your seedlings or clones in a big container. This is because it’s easier for a small cannabis plant roots to get the right mixture of air and water when they’re not waterlogged in a big container.
Small Cannabis Plants Grow Faster in Small Containers
But if you do start small, you need to transfer your plants to bigger containers as they grow to ensure the roots have plenty of room to expand. When roots don’t have enough room, they’ll eventually form a “wall” around the edges of the container. This can cause an array of strange root problems.
If left in a container too long, the cannabis plant will actually become “root-bound.” Think of it as if the roots are choking themselves.The plant roots are unable to effectively get the right ratio of oxygen, water and nutrients, and unless the plant is transplanted, the problem continues to get worse as the roots wrap tighter and tighter. Some growers will even use too-small containers to constrict their cannabis plants on purpose and keep them from getting bigger! So when it comes to transplanting cannabis, you want to make sure you transplant at the right time so your plant roots never run out of room. You’ll actually be hurting their growth if you wait too long to transplant!
A root-bound cannabis plant – transplant your plants before it comes to this!
Root-bound cannabis plants grow very slowly and may even stop growing altogether. In addition to proper transplantation, you can prevent cannabis from getting rootbound by growing plants in smart pots (fabric pots) or air pots since they let air in from the sides. This automatically “prunes” the roots around the edges so they can’t form a wall. Plants don’t get rootbound, and tend to grow faster overall in containers like this compared to regular containers, but they need to watered about twice as often as a similarly sized regular pot since the growing medium is constantly being dried from the sides.
Smart Pots (Fabric Pots) & Air Pots Prevent Cannabis From Becoming Root-Bound
They also make it much harder to overwater your plants. The main drawback is they need to be watered much more often than a regular pot. (learn more about them here)
It is really nice that cannabis plants just plain grow faster in pots like smart pots and air pot. I personally recommend them if you can get a bigger size so you don’t have to water as often. Besides solo cups, fabric pots are the only type of container I use for growing cannabis in soil or coco coir! But I digress…
When a marijuana plant is root-bound, it may display a host of seemingly random symptoms such as drooping and nutrient deficiencies, but usually the main symptom is slow growth.
Root-Bound Cannabis Plant in Solo Cup
Drooping, strange leaf symptoms, yellowing and other cannabis nutrient deficiencies can be caused by a too-small container, like the plant pictured below.
The roots are unable to get the right mixture of air, water and nutrients in a too-small container because the roots are wrapped around the edges. The best (and really only) way to fix up a cannabis plant that has become rootbound is to transplant it to a new, bigger container.
Remember, it is okay to plant your young cannabis in a large container right from the beginning if you want to avoid transplanting your marijuana altogether; just know that they may grow a bit slower for the first few weeks compared to if you started them in something small like a solo cup. If you do want to achieve faster growth rates with transplanting, this tutorial gives you a good general guide to make sure you transplant at just the right time, so your plants never get stressed out, and grow as fast as possible.
There’s nothing wrong with planting seeds directly in a big container! The cannabis just grows a little bit slower at first.
How Can I Tell If My Cannabis Plant Is Rootbound?
It can be hard to know exactly when to transplant your cannabis plants into a new container. Here are some scenarios where you might consider transplanting your plants:
- Soil is drying out too quickly – When your container is drying out only a day or two after each watering it means your plant is drinking fast and needs more water than your current container can hold
- Plant is getting root problems – A cannabis plant can start showing root problems when it’s kept in a too-small container or if it’s become root-bound. These root problems can cause the plant to become droopy, or show unexpected leaf symptoms or deficiencies (such as spots or yellowing leaves). Whenever literally everything else is right but you’re still experiencing these problems, it may be a sign you need to transplant.
- Plant has grown a lot or been in the same container for months. If you’re keeping a mother plant for months, or if a plant has doubled in size in the same container, those are signs you may need to transplant to prevent your plant from getting rootbound.
- Plant is tipping over from its own weight. When your cannabis plant is much wider and taller than its container, it’s easy to tip over and therefore should be transplanted to a bigger pot that can hold it steady.
- Plant is just plain too big for container (pics below) – There are some pictures below to give you an idea of what a plant looks like that needs to be transplanted. Some plants are just plain too big for the containers they are in.
Now let me give you a few real-life examples you can use to refer to. The following transplanting pictures should help give you an idea of exactly when to transplant your cannabis plants!
These marijuana plants are ready to be transplanted
This cannabis seedling is ready to transplant – you can transplant a cannabis plant from a solo cup once its leaves reach the edges. Don’t wait much longer than this for a seedling in a solo cup!
This next cannabis seedling is huge for a solo cup – it should have been transplanted weeks ago! The strange curling symptoms are a sign that the roots aren’t happy. Once this plant was transplanted it started growing perfectly again.
Sometimes a rootbound cannabis plant shows strange symptoms that almost look like nutrient deficiencies and/or overwatering, when the real problem is it just needs a bigger container!
This next marijuana plant is also way too big for its solo cup. Although it still looks relatively healthy, notice the yellowing bottom leaves with spots and bluish color. If this plant isn’t transplanted to a bigger container, those leaf symptoms will continue moving up the plant and start causing problems. Additionally, most likely this plant would already be much bigger if its roots weren’t being constrained by the solo cup.
These marijuana plants aren’t showing symptoms yet, but they’re getting too big for their pots and should be transplanted soon, especially before they start flowering!
These cannabis plants are way too big for their containers and they’re starting to show strange leaf symptoms, drooping and curling because roots aren’t getting what they need
When a cannabis plant is much wider than its pot, it should be moved to a bigger container even if it’s not showing signs of being root-bound. Not only will the plant roots love the extra space, your plant won’t be so easy to tip over!
This cannabis plant was not transplanted before it started flowering. Although it was healthy its whole life, in the middle of the flowering stage it started drooping and showing these symptoms, because the plant was rootbound. Although it’s generally not recommended to transplant a marijuana plant in the flowering stage, that’s what was needed to fix up this plant and get to harvest!
Seed to Final Container: When to Transplant
1.) Start seeds or clones in a seedling plug/cube or germination station and wait until you start seeing roots come out the bottom (or skip this step and plant seeds directly in a solo cup).
This grower has waited too long before transplanting to bigger container
(it’s good to transfer once you start seeing roots)
2.) Place young plants in a solo cup with holes in the bottom to allow water to drain freely.
Make sure to cut holes in the bottom of the solo cup first, so water can drain out the bottom easily!
Just dig a small hole and stick the starter cubes directly into the new growing medium.
Allow them to grow a few sets of leaves, until the leaves reach the edges, like this…
Once the leaves have reached the edges of the solo cup, it’s time to transfer to a bigger container to prevent your seedlings from getting rootbound.
3.) Transfer plants to a 1, 2 or 3 gallon pot
Instead of pulling the whole plant out of the container, it’s often easier to just cut away the solo cup when you plan on transplanting. This is one of the advantages of starting in disposable cups – it makes transplanting easy and stress-free.
4.) Transfer again when plants double in height
Plants are ready to transfer again when they have about doubled in height.
They should look something like this…
If you’re growing big plants and your cannabis plants double in size again, you may need to transfer one more time!
5.) Transfer cannabis plants into their final container! That’s it. You’re done with transplanting your weed plants!
Now you just need to worry about taking care of your plants until you’re ready to start flowering/budding. Remember plants will usually double (or even triple) in size from when you first initiate the flowering stage.
Note: You can skip some of the steps in the cannabis transplant guide above. Just make sure you’re careful not to overwater small plants in too-big containers. Once plants start growing vigorously, you don’t need to worry as much about overwatering.
Tips For Easy & Stress-Free Transplanting
- Water your cannabis plants 1-2 days before transplanting. This will help the growing medium stay together (since it’s moist), but still slide out easily (since it’s not soaking wet).
- Before you get started, fill your new pot with potting mix. Don’t fill the pot to the top, instead leave about 2 extra inches (5 cm). That way you can easily water the plant without all the water running off the sides.
- Water this new container of potting mix before you begin the transplant so it’s nice and moist. If you don’t water the new soil first, it can have a hard time absorbing water after the transplant, and your roots won’t like that!
- Since you will soon be adding a new plant, you want to dig out a hole in the middle that’s about the size of your old container.
- Take your plant, and carefully slide a butter knife inside the container all around the edges to help separate the rootball from the sides of the pot. Avoid grabbing the plant directly by the stem. Try to grab the whole top with a flat hand, and turn the container upside down so you can gently pat the rootball out and catch it with your flat hand. You may have to gently pull the plant out of the container, but go slowly and be gentle!
- Plant the rootball directly into the new container, placing it in the hole you dug out earlier. You may need to add some extra soil to ensure a nice flat topsoil.
- Gently pat down around the roots, to help press everything together slightly, then water your plant immediately. If you do it right, it won’t stress your plants at all!
Minimize Transplant Shock
The process of transplanting can shock your cannabis plants, especially if you wait too long to transplant.
Learn how to avoid cannabis transplant shock!
You can help avoid causing your cannabis plants stress during transplant by following these principles:
- Transplant your cannabis plants after their roots have begun to fill container (to help hold all the growing medium together) but before the roots have started wrapping around the edges (plants have become rootbound).
- Water your cannabis plants 1-2 days before transplanting. This will help the growing medium stay together (since it’s moist), but still slide out easily (since it’s not soaking wet).
- It’s better to transfer too early than too late!
- If the roots haven’t grown all around the sides of the root ball (plant isn’t rootbound), avoid disturbing the roots if possible. There’s no need to shake out dirt, just carefully move entire root ball directly into the next pot.
- Make sure your plants are in their final container at least 1-2 weeks before you switch them over to the flowering stage, and avoid transplanting plants during the flowering/budding stage if you can since the stress may affect your final yields.
- If your cannabis plants seem like they are suffering from transplant shock (leaf symptoms, drooping, slowed growth), it can be helpful to use a seaweed kelp extract (often available as a liquid fertilizer) to help your cannabis recover more quickly.
- If transplanting seems scary, it’s okay to plant your seed or clone in its final destination right at the beginning, just be wary of overwatering until the plant is growing vigorously and has a few sets of leaves. You can increase the amount of oxygen available to your plants by adding extra perlite to loosen the soil and allow water to drain through more easily
- Water your cannabis properly after they’ve been transplanted for the best results!
If you follow all these steps, you may notice that your plant doesn’t show any signs of stress at all!
What Size Should my Final Container Be?
This depends on what size plant you plan to grow, since bigger plants require bigger containers, while smaller plants grow fastest in a relatively small container. For the best results, you need to match the size of your plant with the size of your container.
A general guide is to have up to 2 gallons per 12″ of height. This isn’t perfect, since plants often grow differently, and some plants are short and wide instead of tall, but this is a good rule of thumb.
So if your final (desired) plant size is…
2-3 gallon container
3-5 gallon container
5-7 gallon container
6-10 gallon container
8-10+ gallon container
Go Bigger If You Need to Spend Time Away From Your Cannabis
However, if you plan on being away from your plant for more than a day or two during the grow, it can’t hurt to go up a size or two. The bigger the container, the less often you need to water. So even if you get slightly slower growth in a too-big container, you will definitely be able to spend more time away from your plants without having to water them!
Did you know that transplanting your cannabis at just the right time will actually make your plants to grow faster? Luckily transplanting is easy with a little planning, and only take a few minutes!