Transplanting Cannabis Plants: Why, When & How

Transplanting Cannabis Plants

Transplanting cannabis plants is the best way to develop a healthy root mass and ensure vigorous early growth. Whether you are starting from seeds or clones, in soil or coco, plants will do best in appropriately sized containers. This is true for all cannabis plants. There is a persistent myth in the cannabis community that auto-flowers should be started in final containers. However, like virtually all other potted plants, I recommend transplanting auto-flowers too. Unlike the myth, which suggests that it slows plants down, transplanting is a ubiquitous horticultural practice because it speeds plants up and produces better root structure.

In this article/tutorial I cover everything you need to know to develop and execute your transplant strategy for cannabis in soil or coco coir. I explain the benefits of transplanting cannabis plants and the horticultural reasons for the practice. I then describe the various aspects of a well-developed transplant strategy, including how to avoid transplant shock, the best containers for transplanting, when to transplant cannabis and, of course, how to transplant cannabis plants.

The Benefits of Transplanting Cannabis

Plants do best when grown in appropriately sized containers. This is true about all plants in all media, but it is particularly true about cannabis plants. In both soil and coco, transplanting helps promote the ideal conditions for early growth. Keeping small plants in small containers makes it easier to achieve the correct air to water ratio and encourages denser root growth. The risks of transplant shock are minimal even for new growers. Therefore, the benefits of transplanting cannabis plants clearly outweigh the risks.

The Benefits of Transplanting Cannabis Plants in Soil

When growing plants in soil, transplanting is critical for several reasons. As with any media, plants started in small containers grow faster, develop better root ball mass and greater root density. However, in soil, there is an even more important reason to start small and pot-up: air to water ratio.

Transplanting Promotes the Best Air to Water Ratio

One of the key benefits of keeping small plants in small containers is that they do not become water-logged. Soil retains too much water, and roots suffer from oxygen deprivation immediately following watering. With large plants, the roots themselves help absorb the water and keep the soil from remaining water-logged. However, when small plants are in large containers, they cannot absorb sufficient water through their roots and the soil remains saturated. This will stunt root growth and can lead to “damping off” and eventual plant death.

New growers often think that starting a plant in a large container of soil will be the easiest way to grow. However, you really need to be an expert gardener to be able to water small plants in large containers of soil without over or under-watering. The truth is that it is easier to learn how to transplant than it is to effectively water small plants in large containers.

The Benefits of Transplanting Cannabis Plants in Coco

Coco coir mixed with perlite is an incredible growing medium because it always retains enough oxygen in the media. This means that even after a watering the roots are not water-logged; they still have access to oxygen. However, the air to water ratio is still superior when the plants are in the appropriate sized container. Furthermore, air to water ratio is not the only benefit to transplanting. As with almost all plants in almost all media, transplanting cannabis plants grown in coco is critical to help promote the best root structure and root ball mass.

Transplanting Cannabis Produces the Best Roots

When plants grow in containers, their roots quickly seek the bottom and colonize primarily along the bottom of the container. Transplanting through a series of steps encourages roots to colonize the full volume of media.

You can think of potting-up through a transplant strategy as being a form of root training. At each step, the plant establishes a new zone of root density before potting-up. This creates a final container that has root density throughout the volume of the media rather than primarily at the bottom.

Small containers early in life encourage root ball formation and lead to greater density of roots throughout the plant’s life. Conversely, if a small plant grows in a large container it will send roots to the bottom. This leaves a huge vacant mass of medium with relatively few roots. As a result, the medium takes longer to dry and there is less oxygen available to the roots. The roots will not colonize the middle of the pot after they have grown past it. Therefore, starting plants in a large container effectively reduces the potential root area and the potential harvest.

Seedlings Grow Slowly in Large Containers

Starting plants in large containers not only limits their potential, but it also slows them down. Large containers often do not retain adequate oxygen for root growth in the center of the media and the roots will grow at the edges and the bottom. This forces seedlings to invest additional energy in root growth at the expense of above ground growth. Since the above ground growth is the source of all energy, this has a compound effect in slowing vegetative growth early in life.

Starting seedlings in small containers and potting up encourages more balanced and faster growth. Roots quickly reach the bottom and colonize the seedling pot allowing the young seedling to work on above ground growth. Potting up to a second container and then the final container continues this process of balanced growth and root colonization.

What about “Transplant Shock”?

Many growers avoid transplanting because they are worried about “transplant shock”. However, even new growers can completely avoid transplant shock when potting-up. In fact, transplant shock as a horticultural phenomenon is not related to the style of transplanting that we practice. We are “potting-up”, which is simply moving a plant to a larger container with the same medium. If we take basic precautions with the roots and the medium, then the plant will not suffer any transplant shock.

Transplant Shock Can be Avoided When Potting-Up

Transplant shock is usually a result of significant physical root damage during the transplant process. This often occurs when plants are excavated from the ground to be re-planted in a different location. In that style of transplanting, the tap root often suffers significant damage. Fortunately, with indoor cannabis, we are not doing that style of transplanting.

New cannabis growers often worry about damaging roots during transplanting. However, the root damage that occurs when plants are potted up is usually peripheral. This slight damage to peripheral roots does not lead to transplant shock. Indeed, a little root pruning helps encourage fibrous root growth. If you follow the procedure and timing that I explain below, you can safely pot-up without fear of transplant shock from root damage.

Take Simple Steps to Avoid Shocking the Roots

The other cause of transplant shock is “root shock”. This usually occurs because plants encounter different fertilizers or an unfamiliar medium in the destination. Root shock often affects garden starters that are started in seedling pots and then transferred to garden beds. It can also affect cannabis plants if the transplant medium is not properly prepared.

With simple precautions, growers can completely avoid “root shock” when potting-up. We are not changing the medium, just increasing the volume of it. However, it is important to ensure that the new media is set to the same parameters as the current media for the plants. You can accomplish this in coco or soil by pre-watering (fertigating) the new media with the same nutrient solution that is used for the plants. Be sure to measure the Electrical Conductivity (EC) of the water that flows through the new media (the run-off) and verify it is appropriate prior to transplanting.

Root shock can also occur if the roots are exposed to light and air for long durations during the transplant process. As a result, you should always get the new container prepared in advance and execute the transplant process quickly. If the transplant is done quickly and the new media has the same fertilizers and EC, then the roots will not be shocked. Rather than suffering transplant shock you can expect to see a growth surge immediately after you pot-up.

Transplanting Auto-Flowers

If you grow Auto-flowering cannabis plants, it is important to grow them quickly. They will begin to flower on their own schedule and if they are stunted then there is no time to recover. This makes it particularly important to follow a transplant strategy when growing auto-flowers.

There is a persistent myth in the cannabis community which argues that auto-flowers should not be transplanted. This myth is based on the false premise that transplanting leads to transplant shock and slows plants down. The reality is that we use a transplant strategy in horticulture because it produces faster and better growth. Auto-flowering cannabis plants are not some unique exception to this rule. Like virtually all other potted plants, auto-flowers grow faster and better using a transplant strategy.

Transplant Strategy for Cannabis

I recommend a three-stage transplanting strategy for most cannabis plants in soil and coco. The initial seedling container is small to allow the young plant to quickly develop a root ball mass. The second stage allows the roots to expand as the plant grows, but only a little. Once the roots colonize the second container, the plants are ready to be potted-up into their final container. They will move into their final containers with a significant root ball mass which will be their foundation for healthy and vigorous growth through the remainder of vegetation and flowering.

Pots: Containers for Transplanting Cannabis

You should consider the material and size of the container when choosing pots for your cannabis transplant strategy. The material of the container will affect the plant growth and the difficulty of the transplant process. The pot size that you should choose as you pot up is determined largely by the medium that you use. Plants growing in coco do better in a smaller second container than plants growing in soil. Choosing the best containers for transplanting ensures the easiest transplant process and the best plant growth

Container Material: Plastic or Fabric Pots

I prefer fabric pots or air-pots for the plants at every stage. These containers offer the best drainage and aeration. This helps maintain the best air to water ratio, which promotes the best root growth. Many growers are concerned with the difficulty of transplanting out of fabric pots. However, in practice, they can be just as easy if not easier than transplanting from plastic. I offer a step-by-step transplanting guide below.

Pot Sizes for Coco Grows

  • Coco Stage 1: Seedling Pots: 1-Pint
  • Coco Stage 2: Half to One-Gallon
  • Coco Stage 3: Final Containers: Three to Seven-Gallon

Coco coir offers roots an ideal growing environment with very little resistance. As a result, roots grow very quickly during early life. If the roots have a lot of room to expand into, they will spread out quickly. That may sound great, but it is not ideal for developing the best root mass. In order to develop a denser root mass, it is beneficial to go through 3 steps rather than directly from a seedling pot to a final container. The second step should be relatively small to prevent run-away roots and develop better root density.

Container size does not limit the plant size when the medium is coco. Instead, the ideal final container size in coco depends on your watering frequency. Three-gallon final containers are best if you practice high-frequency fertigation with an automatic watering system. Five or seven-gallon final containers are better for hand-watering.

Pot Sizes for Soil Grows

  • Soil Stage 1: Seedling Pots: 1-Pint
  • Soil Stage 2: Two to Three-Gallon
  • Soil Stage 3: Final Containers: Five to Ten-Gallon

Plants in soil should start in the same small seedling containers that coco growers use. However, soil offers less root space than coco, so as they mature the plants benefit from larger pot sizes. The second step for a soil transplant strategy should be two to three gallons. This gives the plant room to expand its roots but is small enough that it will not lead to over-watering issues.

Container size limits the final plant size when the medium is soil. Therefore, the best final container size depends on the size of the plants. Most indoor soil growers do well with five, seven or ten-gallon final containers.

The Best Pots for Transplanting Cannabis

Seedling Pots

Fabric Nursery Bags
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The best option for seedlings is fabric nursery bags. They provide a great environment for root development and are very easy for transplanting. To transplant I cut the bottom open and slide the media into its second fabric pot. The alternative is to use plastic "solo" cups with lots of holes punched into the bottom for drainage. However, we highly recommend the fabric nursery pots for the best growth.

Second Containers

1-Gallon Transplanter Pots
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The second containers that I use are no longer available. But these transplanter bags from 247 Garden seem to be even better. Transplanter pots have a velcro seam up the edge, which allows easy removal of the pot for transplanting! This is a set of five 1-Gallon transplanter pots. They are also available in 1/2 gallon and 2-Gallon.

Final Containers

When choosing final containers the media needs to be considered. For coco grows the first concern is drainage. Smaller containers drain better, but require more frequent watering. In most coco grows, 3 or 5-gallon final containers are best. For soil grows, root space is more limited, so larger pots are required for larger plants. We recommend 5-10-gallon final containers for soil. For both coco and soil we recommend either Air-pots or fabric pots because they drain well and create the best environment for roots.

#3 Air-pot
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I think these are the best container for growing in coco with an automatic watering system. They are a perfect final container for Autoflowers or Photo-period plants with less than a 6 week vegetation. You should be prepared to water up to 6 times per day with these.

#5 Air-Pot
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These pots will work great for coco or soil grows. With coco you should plan to fertigate between 2 and 5 times daily. For soil, you should plan daily fertigation. These are the containers that I am currently using with coco. They are the reason that I recommend Air-Pots. The roots that plants grow in these pots are healthy and impressive. Air-pots are a little expensive compared to fabric pots, but I really think they are worth it.

7-Gallon Fabric Pot
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These are the most versatile and least expensive final containers for soil grows. They are also suitable for coco growers who are hand-watering and limited to once daily fertigation.

When to transplant Cannabis: Potting-up

The best time to transplant cannabis plants into a larger container is when their roots have established a root mass in the current container. If you transplant the plants too quickly then it eliminates the advantage of the transplant strategy. Conversely if you transplant too late it can slow growth, which also reduces the advantage of transplanting. Although the roots are the key, you can estimate the best time to transplant by observing the above ground growth.

Stage 1: Seedling Containers Until the Plant has Three Nodes

I recommend starting seeds in a germination media such as Jiffy Pellets. Be sure to see our tutorial, “How to Germinate Cannabis Seeds” (Coming soon). When the root emerges from the jiffy pellet, it can be transferred to the seedling pot with soil or coco. Healthy plants will fully colonize a one-pint container by the time they have grown 3 true nodes. This will take about a week in coco and somewhat longer in soil. The roots may emerge from the pot earlier than this, particularly when using coco in the fabric seedling pots. That is not a problem and it is not a sign that you should transplant earlier. The roots may come out the bottom, but that does not mean they have colonized the full volume of the container. When the plant has three nodes it is safe to pot-up to the second container.

Stage 2: Second Containers Until the Plant Doubles in Size

The second step in the transplant strategy is important to nurture the growing roots and develop the best root mass. Although the pot sizes are different for soil and coco, the general rule about when to transplant is the same. Plants should at least double in size in their second container before potting-up. If a plant has three nodes when it comes into the second container, then it should have six or seven before you pot up. When plants are growing very well this may take less than a week. That doesn’t mean the second step was pointless, rather it means that it worked brilliantly!

How to Transplant Cannabis Plants

The actual practice of transplanting is straight forward and easy to master. It should not intimidate growers and does not need to be traumatic for the plants. Different media and different containers must be handled differently, but the basic principles are largely the same. Here, I provide a step-by-step guide to transplanting cannabis.

Transplanting Cannabis Step-by-Step

Step 1: Prepare the new container and media

The first task is to prepare the new media in the new container. The goal is to create a medium with the same nutrients, Electrical Conductivity (EC), and pH as the plants already experience. Depending on the media, this may be as simple as filling the pot and getting it wet or it may require pre-fertilization and measurements.

Fill the pot with the new media but leave some space for the transplant. The new media should be thoroughly saturated at the time of transplant. If you are fertigating your plants (adding fertilizers to the irrigation water), then the new media should be saturated with the same nutrient solution that the plants have been receiving.

When you saturate the new media, you should collect some of the excess that runs-off and measure the EC. Coco that comes straight from the buffering process is often too high in EC for the plants. It is common to get new soil that is too high in EC as well.

High EC in the new media is the main cause of “transplant shock”, but it can be completely avoided. If the EC reading is outside the current range for the plant, then continue to flush the new media until the run-off EC is in range.

Once the media is saturated and the EC is confirmed then it is time to make a hole to receive the plant. I usually dig out the hole with my hands and push the media into the edges of the pot. Be sure to make the hole larger than the current pot. You can eyeball this or actually lower the plant into the hole while it is still in its container to judge the size.

Step 2: Prepare the Plant

In soil, I recommend to allow the plant to dry out somewhat prior to transplanting. This can help to reduce root damage and ease the transition to the new media. However, I do not advise this in coco. Coco should always stay wet and being wet helps the coco to stick together better during the transplant process. Because of this, I fertigate my plants in coco immediately before transplanting them

Before attempting to remove the old container, it helps to separate it from the plant and medium. In most containers you should be able to slide a butter knife, or other similar tool, around the inside edge of the pot. If you are growing in fabric pots, you may cut through several roots while doing this. It is not a problem to cut these peripheral roots.

Step 3: Remove the Old Container

The standard procedure to remove the old container involves flipping the plant upside down momentarily. Simply cover the top of the media with your hand as best as you can. Then flip the plant over and pull the pot off the media. Plastic pots will come off easily, but fabric pots may need to be worked off the media with some caution.

The easiest way to remove fabric pots is to use scissors and cut them. The fabric seedling bags are very cheap, so I use scissors and cut the bottom out of the bag. I then cut a slit up the side and peal the pot away. The second containers are more expensive and durable, so I try to save them. The “Velcro transplanter” pots make removing the containers much easier. If you do not have transplanter pots, you can turn a standard fabric pot into a “transplanter” pot by cutting a slit up the side. Afterwards, you can close the slit with safety pins to use the pot again.

Step 4: Transfer to New Container

This step should go quickly! Simply take the pot-less plant and media and place it in the hole that you prepared in the new container. Fill-in the hole by pushing the media down from around the sides. That’s it, transplant complete!

Step 5: Post-Transplant

Following the transplant, you should monitor the plant and ensure it is growing well before resuming any plant training. Most plants will perk up and grow happily in their new containers. If they are happy then you can resume training and topping 24 hours after the transplant. However, if the plant is a little grumpy about the transplant, give it time to recover before applying additional stress.

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Author: Dr Coco

I am a university professor and have taught courses in horticulture. I am coco for cannabis and I hope you are coco for cannabis too :) Grower Love!