When to transplant cannabis and how to do it

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Dani Alchimia

Whether in an outdoor indoor cultivation, transplanting cannabis is a sensitive phase in the life of your plants, which need enough space to develop an extensive root system in order to reach their full potential. A plant with little room for its roots will never perform as well as another with a well-developed root ball! For this reason, it’s a very important moment for the plant growth, and you must transplant your marijuana at the right time and into the right pots.

Today we are going to take a closer look into this operation, which must be carried out with utmost care in order to minimize the stress caused to the plant. If you do it right, you will be able to make the most of the available space, save substrate and nutrients, reduce the risk of fungi, accelerate plant development, and obtain maximum yields… It’s worth trying, don’t you think? Let’s do it!

Healthy roots need some basic care

Healthy roots need some basic care

Why transplant your cannabis?​

In nature, cannabis seeds germinate and rise directly from the ground after winter; these plants usually grow without any restrictions in regards to space for their roots, which can freely develop in all directions. This way, in addition to being able to better withstand the lack of irrigation, the plants grow and flower unrestricted, potentially reaching very big heights and yields with just some basic care.

However, when growing in pots you are limiting the space available for their roots, which naturally affects the plant’s overall development, both in the aerial part and the root system. Unsurprisingly, a plant cultivated in a small pot until harvest won’t yield as much as another plant that has plenty of room to develop a healthy root system, since the link between the size of the pot and the size of the plant is quite clear; but, why not germinate the seeds directly in large containers? Why keep changing pots periodically?

As we have already mentioned, if you do it right, you’ll be able to enjoy a number of benefits, among them:

You can save space, nutrients and substrate: when starting you cannabis grow, you don’t need large pots or huge amounts of soil. A straightforward 1L (or even smaller) container is more than enough for the first stage of your plant’s life, until it develops 3-4 sets of leaves. As you won’t need so much substrate or nutrients as with larger pots, the savings are obvious. Also, during this first phase, you probably won’t need much space or light, and certainly much less than during the vegetative and flowering phases, or if you start growing in a big pot and in a much larger cultivation area.

When growing in smaller pots you’ll save space, substrate and nutrients

When growing in smaller pots you’ll save space, substrate and nutrients

Growing speed: when cultivating cannabis in a relatively small pot, you need to water your plant more often than with larger pots. When the dry substrate/wet substrate cycle is repeated more often, it results in a phenomenon similar to hydroponic cultivation: the more you water a plant, the faster it grows. It’s a matter of maximising this period until the transplant becomes necessary for the reasons we’ll see later on.

Lower risk of pathogenic fungi: imagine you sow marijuana in an 11L pot; if you moisten the whole substrate, it will be wet for several days, and given there are hardly any roots to absorb the moisture, it will take a long time to dry. This – especially when over-watering – can result in an increased risk of the roots developing pathogenic fungi, something that every cultivator would want to avoid at all costs.

Better performance: on the one hand, if you transplant your cannabis at the right moment using the right type of pot (basically, big enough for the plant you are growing), you’ll maximize the plant’s production. On the other hand, and as we have seen, when speeding up the process, you will save a few days at the end of the cultivation period, which will also improve the setup.

The same clone of the previous photo a few days after the transplant

The same clone of the previous photo a few days after the transplant

How many transplants do cannabis need and when to carry them out?​

Generally speaking, a marijuana plant is subjected to 2-3 transplants throughout its life cycle. A classic example of indoor cultivation would be a 1-2L pot followed by a 4L pot, and a final 7-10L pot. This could vary depending on the cultivation method and the grower needs and preferences, as it won’t be the same using the SOG than the SCROG techniques! Larger pots are usually used outdoors, where you can begin with a 3-4L pot followed by a 10-15L pot, and end with a final container of your chosen size (the larger the latter, the sooner you’ll have to perform the last transplant, so the plant has time to adapt and develop the maximum amount of roots before flowering).

In regards to the best moment to transplant cannabis, several indicators will let you know the time is right:

  • Roots condition: when the roots start filling the pot’s drainage holes (and even sticking out through them), this is a symptom that they need more room to continue expanding.
  • Plant size and structure: in the case of a poor or non-existent horizontal growth (lateral branches), it could be necessary to move the plant to a larger container. And the same applies when the plant begins to stretch; it’s very likely that it needs more space for the roots.
  • Irrigation: when the plant has colonized all the substrate with its roots, it could barely retain moisture, so you should water it more often (every day or even several times a day). This is a clear sign that your marijuana needs transplanting into a pot with a bigger amount of substrate.

All these symptoms can overlap and take place simultaneously, something that is very common. If you monitor any of them, you’ll know whether the other signs are also present, which would confirm 100% the need of transplanting. But… how do you transplant your cannabis causing minimal stress to your plants? Which pots are most suitable? We explain this below!

This plant is beginning to need transplanting

This plant is beginning to need transplanting

Pots sizes​

As you know, the market provides plant pots of many types and sizes, from small containers for germination to large receptacles with a volume of hundreds of litres. As a guide, we propose the following pot sizes depending on the chosen technique:

Indoor transplants​

Depending on the chosen cultivation method, the size of the final container can differ greatly. Here are some examples:

  • SOG: 0.5L pot, followed by 1.65L pot, and a final 3.25L pot. Remember that the purpose of this method is to grow many small-sized plants with a single main central cola.
  • SCROG: in this case, you can start with a 1.65L pot, followed by a 3.4L pot, and depending on the number of plants, a final 10-20L pot. Here we are aiming for a few large plants.
  • Standard cultivation: many growers use a mixed technique, with more plants than in SOG but less than in SCROG. You can start with a 1L pot, move to a 2.5L pot, and conclude with a 4-7 litres container; again, depending on the number of plants you are growing.
Depending on the cultivation method, you can choose a different type of container

Depending on the cultivation method, you can choose a different type of container

Outdoor transplants​

Similar to indoor cultivation, the pot size will also have a strong impact on the dimensions and production of the final plant. As we have seen, outdoor cultivations use larger pots than indoor grows from the beginning, as the vegetative period is much longer than when cultivating under artificial lights. For this reason, outdoor plants sometimes need more transplants, especially during the early stages of the vegetative period.

Either way, you need to apply the same criteria to determine whether the transplants are necessary or not, trying not to delay the right moment so the plant’s growth rate does not drop. It may also happen that after several transplants you’ll end up growing on the ground. In this case, we recommend you to perform the last transplant as soon as possible, in order to achieve maximum root growth (just like when using a final pot of more than 60-70L). To accelerate this process, and especially when growing on the ground or reusing a substrate, adding microbial life can greatly help with root growth.

How to transplant cannabis​

Let’s have a look now at how you can transplant cannabis causing the least possible stress to your plants. Remember that, on the one hand, you are placing your plant in a new location with more room and nutrients, but on the other hand, you are causing stress by tampering with it and taking it out of its old “habitat”. Ideally, you should water it 1 or 2 days before performing the transplant; if the substrate is too dry, it could come apart when extracting the root ball, whereas – similarly – if it’s too wet, it could crumble. You need to achieve a medium humidity level.

A great trick to cause minimal stress is to proceed as follows: fill the new pot with soil until when placing the old pot on top, there are still 2-3cm of the new container above the plant. Leave the old pot in the substrate and continue filling the new one until it’s completely covered, as if you’d wanted to bury the old one. Water the new container’s substrate, and carefully remove the old pot, so there’s a hole in the substrate which is a “mould” of the plant’s root ball. The only thing left to do is carefully remove the plant from its old container and place its root ball in the hole you made in the substrate. Cover everything with 1-2cm of soil and water a little more. You’re ready!

Usually after each transplant, root stimulators are used to maximize root growth and promote the plant continuous development. As we have pointed out, you can also use microbial life, such as beneficial bacteria or fungi, to speed up this process.

And here we end our article on how, when and why to perform a transplant. As you can see, if it’s done at the right moment and in the right way, the final yield can increase considerably. Don’t hesitate to share your transplant tips and techniques with us.

Happy growing!

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