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Image by Felipe Vieira
Writer's pictureJim Jones

How & When to Transplant Cannabis Seedlings?

Updated: Oct 17

Transplanting cannabis seedlings from their initial germination medium to a different pot is crucial for their development. As a weed plant grows, it needs space for the roots to spread out, collecting nutrients to grow to its full potential size. Failure to transplant correctly can lead to stressed weed plants, stunted growth, or even death. This introductory guide will highlight the importance of transplanting at the right time and the negative impacts of neglecting to do it correctly.

TL/DR | Key Takeaways

  1. Monitoring seedling development through roots and node growth is crucial for optimal transplant timing.

  2. Choosing the right container size and material helps promote healthy plant growth.

  3. Using techniques that minimize transplant shock and maximize root development is essential.

  4. Using proper container sizes for your cultivation goals is as important as monitoring stresses and root systems.

When is it the Right Time to Transplant Cannabis Seedlings?

Cannabis cultivation is an art and science; pinpointing an exact transplanting date isn’t always feasible. My rule of thumb is to consider transplanting young plants just before they outgrow their container. Roots poking out of the bottom indicate it’s time to repot. When the true leaves of the seedling cover the circumference of the container, it’s time to transplant. Don’t wait too long, as rootbound marijuana plants can be permanently stunted.

Look for specific signs from your seedlings to determine the right time, and consider the following:

Transplanting Autoflower Seedlings vs. Photoperiod Seedlings

When transplanting autoflower seedlings, it’s crucial to place and/or germinate them directly into their final container to minimize stress and ensure optimal growth. Autoflower plants, as opposed to regular photoperiodic ones, have a limited vegetative period. Any disturbance will hinder their development since autos have less time to recuperate and re-establish themselves after stress.

The size of the final container also significantly influences the overall size and yield of the plant. A larger container allows for the development of a more extensive root system, which supports a bigger and healthier plant. For best results, choose a container size that balances your space limitations with the potential growth of your autoflowers.

What Size Pot or Pellet is Your Weed Seedling In?

Timing depends on the size of the starter pot. Seedlings take 7-10 days to outgrow small pots. Quickly transplant pellets to keep your plants from stretching; with a solo cup, you can wait until the seedling has around three true sets of leaves. Use these pointers as a guide, but the best practice when transplanting cannabis plants is to keep an eye on your plants.

Is Root Development Visible and Robust?

The classic saying is, “The bigger the roots, the bigger the fruits.” It means healthy roots are crucial for a plant’s growth. The size and structure of the roots can indicate the plant’s health. The color is also important; healthy roots are milky white.

The roots should be wrapped around the growing medium if your seedlings are in small pots, such as solo cups. If you have used starter pellets, you should be able to see the roots poking out the bottom.

Hemp plant rooted in a soil clump

Cannabis plant in a soil block with visible roots.

Choosing the Right Container to Transplant Your Weed Seedlings

Selecting the correct container is crucial since it influences your seedling’s health, efficacy, and growth.

Assorted Pots for Cannabis

Various options of Cannabis Pots.

Choosing the Right Pot Size for Your Cannabis Seedling

The pot size you choose for your baby plants will impact their root development and overall health. A general rule of thumb for size would be:

  1. Small plants & Seedlings: 2-3 gallon pots

  2. Medium plants: 3-5 gallon pots

  3. Large plants: 5-10 gallon pots

When choosing a size for your pots, consider the environment you’re cultivating and see what works best. If you want to grow many plants in a confined space, you may opt for small/medium pots for the final container. If you focus on growing large individual plants, get a larger pot. Remember: “The larger the roots, the larger the fruits!”

What is the Best Material for Cannabis Plant Containers

The material you choose for your pots will affect moisture retention and breathability. Fabric pots offer excellent drainage and air circulation, which helps maintain healthy root systems. My pro tip is using fabric pots since they are softer for roots as they push against the container. They also give you a good idea of how much water is in your pot when you feed. On the other hand, plastic pots with drainage holes are easy to move and cost-effective, though they aren’t very porous and have problems with breathability.

How to Transplant Weed Seedlings to Their Next Container

When your seedlings are ready to be transplanted, in general, it’s a matter of making a hole big enough to incorporate the rooted cannabis seedling within the new medium. However, below are a few considerations to keep in mind:

When Transplanting Peat Pellets into Soil Mix

Peat pellets are designed to be transplanted directly into their next medium to reduce transplant shock. When transplanting these, make a hole in the final medium that’s the same size, if not slightly larger, than the size of the pellet. Then, place the pellet in it and cover it with more soil before watering.

How to transplant Jiffy Peat Pellets

The Process of Moving Jiffy Peat Pellets to Another Growing Area

When Using Rock Wool Cubes

When using Rockwool cubes, you need to buffer your cubes in a nutrient/water solution since these cubes dry out quickly. Afterward, drain the cubes to ensure they maintain a proper amount of nutrients and pH balance. Make a hole the size of the plug you used and transplant it into that final cube.

How to Transplant Rockwool Cubes

Transplanting Rockwool Cubes into a slabs is an option.

Transplanting Into Coco Coir

Initially, you should fill half of the pot with coco before transplanting. Similar to soil and rock wool, water your coco before placing the seedling. After watering your coco, drain it to ensure a proper balance of pH and nutrients. Then, place your plug/plant into the coco, fill it until the base of the plant is covered in coco, and water it over again to saturate the medium.

How to transplant Coco Pellets

Moving Coco Coir Pellets to a New Growing Environment

When Planting Outdoor

If you’re starting your plants indoors and transplanting them to an outdoor environment, you must give them at least 4 feet (1.25 meters) of space and plant them early in the outdoor season to ensure taller, wider plants that produce more biomass. I recommend starting your seedlings in a small 1-gallon pot, so they grow larger before exposing them to outdoor elements. After two weeks, transplant a seedling from its container into the outdoor medium you’re using, whether in the ground or a larger 10-20 gallon pot.

A marijuana plant maturing in the scenic countryside of Colorado.

A marijuana plant thriving in the rural landscape of Colorado.

How to Prevent Transplant Shock in Cannabis Seedlings

Transplant shock occurs when stresses hinder the growth of the cannabis plant. It’s caused by disturbed roots or when the plant itself is messed with too much. To avoid shocking your plants unnecessarily, keep it simple. I recommend limiting the number of times you transplant your plants and watering the soil lightly before and after the process.

Cannabis Plant Suffering from Transplant Trauma

Cannabis Plant Experiencing Transplant Shock.

How Many Times Should You Transplant Seedlings?

In most cases, you should transplant your seedlings twice. First, they should be transplanted into a small one- to two-gallon pot and then transferred to their final pot when they outgrow the first one. If you are growing multiple pots of the same plant, it’s possible to start them in their final container so they go through the vegetative and flower stages simultaneously. Remember, if you are growing autoflowering cannabis plants, you can still start them in pellets or cubes. Still, because of their shorter lifecycle, you will want to transplant them directly into their final container.

Top Tips When Transplanting Cannabis Seedlings

  1. Always handle your seedlings gently to reduce stress on the plant.

  2. Ensure you don’t overwater or underwater your medium post-transplant (this mainly applies to soil).

  3. Choose a pot size and a medium to transplant into that works best for your cultivation style!

Conclusion

Properly transplanting cannabis seedlings sets the pace for your successful cannabis growth. Understanding and learning when and how to transplant your weed plants lets you maximize your plants’ growth potential and produce high-quality buds. Whether you are a novice or a seasoned veteran cultivator, paying attention to the needs of your plants when helping them grow will ensure proper and abundant yields.

Happy Growing!

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