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The Science Behind Transplanting Cannabis Seedlings

May 31, 2023

Do you know how and when to transplant cannabis seedlings? Or why this step is essential for getting sticky buds?

Transplanting lets young weed plants expand in all directions. Without it, seedlings become rootbound, sickly, and slow to grow. Do it right, and you’ll see explosive rates of vegetative development and bountiful harvests.

Keep reading to learn how to transplant seedlings. We discuss timing, techniques, and handy tips to help you get it right.

Planting weed seedlings: What is the ideal environment?

The seedling phase is one of the cannabis growth stages after the seed germinates and before vegetative growth. That produces a plant  stem, root system, and leaves during this time.

Seedlings are delicate and enjoy the following conditions:

  • Warm temperatures: Your space should be toasty but not too hot. Aim for a 70–80°F temperature range during the daytime and 60–70°F at night.
  • High humidity levels: Seedlings enjoy higher air moisture levels, thriving in 65–70% relative humidity.
  • Frequent but modest watering: Young plants have short root systems that can’t absorb plenty of moisture. Dampen the medium every time it becomes dry, but don’t saturate it.
  • Little to no nutrients: Seedlings perform best in lightly fertilized soil. They’re susceptible to burns, so use tiny doses of organic solutions.
  • Long periods of gentle light: Early-stage cannabis performs best under a 20/4 day-night schedule (18/6 after the first transplant). Fluorescent lamps and dimmed LEDs are the best grow lights for young plants. 

Frequent problems with seedlings include damping off, pest attacks, nutrient burns, and overstretching. Being rootbound is another common issue, occurring when the roots tangle and choke due to a lack of space.

Moving young plants to larger containers resolves several issues in one fell swoop. Let’s see when to transplant weed seedlings for the best results.

how to use super soil for cannabis

How do I tell when to transplant cannabis seedlings?

Transplanting cannabis gives it room to spread out and supercharges development. It also protects seedlings from becoming rootbound and dying.

This step is indispensable but can harm cannabis if it happens too early or late. Look for the following signs when considering how long to keep seedlings in solo cups:

  • Roots protruding from drainage holes: As roots outgrow their container, they start peeking out from the holes at the bottom. Loosen the plant from the pot, lift it up, and inspect them for size.
  • Stunted growth and sickly plants: Roots can’t absorb nutrients if stuck in small pots. This issue results in slow growth, discoloration, and deficiency symptoms.
  • Soil drying out too quickly: If you notice the need to water your seedlings every day, the container is likely too small.
  • Cotyledons yellowing and dying: The first rounded leaves lose color and droop as the plant matures and becomes ready for a transplant.
  • True leaves appearing: The seedling develops its initial fan leaves around the time it’s ready for a transplant.

The rules apply to determining when to transplant cannabis seedlings from jiffy pellets or other rooting cubes, 1-gallon pots, or Rockwool. The plants exhibit clear signs of outgrowing their environments and needing more space, usually at 2–3 weeks old and 2–3 inches tall.

Transplanting cannabis

How to transplant cannabis seedlings

Moving seedlings from one container to another is crucial to cultivation. While it may vary with the growing medium and pot size, some general principles apply across the board. Let’s break this process down into steps.


Transplantation is stressful for cannabis. Preparation lets you minimize the potential damage and increases your chances of success.

Knowing when to transplant a cannabis seedling helps you minimize shock. Do it in the morning or evening, but not in the hottest parts of the day. That way, your plant has a few hours to adjust to its new environment before experiencing full sunlight.

Water your seedling soon before transplanting, ensuring the soil is still moist when you move it. This technique ensures the root ball is damp and easy to manage as you move it.

Clean your space of contaminants before transplanting. Sterilize your new container, tools, and work area with mild, plant-safe soap to avoid exposing the roots to pathogens.

Choose a proper pot size

Starting marijuana seeds in solo cups is the go-to for most cultivators, but they soon outgrow this tiny space. When it’s time to move them, you have two options:

  • Gradual transplanting is a technique where you transition your plants into successively larger pots over time. Cultivators usually progress between solo cups, 1-gallon, 3-gallon, and 5-gallon pots.
  • Final pot transplanting means moving the plant directly into its final container. This method requires less effort, but requires you to learn how to water seedlings in big pots. It’s the go-to for autoflowers, as they’re more susceptible to transplant shock.

Once you determine the method, it’s time to pick the size. Go for a pot 2–3 times larger than the current one for gradual transplanting. If moving seedlings straight to the final container, use 2–3-gallon pots for autoflowers and 3–7-gallon for photoperiods.

how much space does a cannabis plant need

Tip: Transitioning plants to final pots is better if learning how to transplant autoflowers. These fast-growers don’t take well to shock and respond better to this technique.

Fill the new container

Fill your container with a nutrient-rich, well-draining soil mix at 6.0–7.0 pH. You can purchase it from a gardening store or create it at home with loamy soil and organic amendments.

Pre-moisten the soil to make it more welcoming and malleable. Fill approximately 75% of the container, and leave enough room on top for the root ball. Create a hole in the center with your fingers or a small shovel.

Pro tip: You can use the container your seedling is in to determine the hole size of the larger pot. Place the previous container in the center and surround it with soil. When removed, your seedling will have a perfectly formed spot.

transplanting cannabis seedlings

Transplant the seedling

Once everything’s ready, it’s time to re-house your seedling. This step is the trickiest, so take it slow and use a gentle touch to minimize risk.

Here’s how to plant a cannabis seedling in a new environment:

  • Remove the plant from its old home by placing a hand around the stem, turning the container upside down, and gently tapping the bottom.
  • Loosen the soil around the roots with your fingers or a fork. Doing so encourages them to grow into the new soil more easily. You can also gently break up the roots, especially if they’re tangled.
  • Place the plant in the new pot and ensure the top of the root ball is level with the soil surface.
  • Backfill the hole with soil, making sure to cover the roots completely. Press down lightly to eliminate any air pockets.

Help the plant settle and avoid shock

Transplanting is a stressful experience for plants. Learn the basics of caring about seedlings to help them settle into their new environment.

After planting weed seedlings, water them thoroughly to make the transition smoother. Focus on minimizing stress for the next few days by providing shade, handling them minimally, and feeding gentle fertilizer.

Helpful tips on how to plant a cannabis seedling

Learning to transplant cannabis seedlings can feel like an art, as it takes some practice to get everything right. Here are some tips to bypass common errors:

  • Use a consistent soil mix: Use a similar soil type and composition in the new pot to minimize nutrient imbalances.
  • Plant at the same depth: When transplanting the seedlings, place them at the same depth as they were in their original container. Having them too shallow or deep causes stress.
  • Prioritize drainage: A waterlogged growing medium cuts oxygen access from the roots and effectively drowns them. Use quality, well-draining soil and avoid overwatering after the transplant.
  • Don’t move plants too early: Err on the side of caution while figuring out when to transplant from a solo cup. The roots are better off tangled than underdeveloped.
  • Provide structural support: The seedlings are unstable after the transplant and may bend or tip over. Use plant stakes or ties to keep them upright as they settle.
  • Add beneficial amendments: Beneficial fungi or bacteria can help reduce shock and increase root growth. Silica may also alleviate stress during transplanting.

Finally, don’t disregard the significance of genetics. Healthy seeds produce prolific seedlings, plants, and buds, making every next step more straightforward.

Visit our store for a selection of high-quality weed seeds. Then use our guides to turn each into a bountiful bud-bearing plant.

Parker transplanting cannabis plants


Do you have any additional questions regarding how and when to transplant weed seeds and seedlings? Below, we answer the common inquiries we hear in the community.

How big should seedlings be before transplanting?

Transplant seedlings once they have robust root systems, 2–3 inches in height, and several sets of seven-fingered leaves. Doing it too early or late stunts growth and may kill the young plant.

The same goes for when to transplant clones from solo cups. Clones are slower to take root than seeds, but the young plant behaves the same after several weeks. Move it to a new pot once it outgrows its current space.

How often do you water cannabis seedlings after transplanting?

Watering frequency for post-transplant seedlings depends on the pot size, growing medium, and environmental conditions. As a rule, wait until the top inch of the medium feels dry before adding water.

Should you let the soil dry before transplanting?

It’s generally better to keep the soil damp during the transplant, as dry root balls are susceptible to stress and transplant shock. We suggest watering 24 hours before moving the plant.

How do you prevent seedling shock while transplanting?

You can minimize the risk of transplant shock with thorough preparation and timing. Knowing when to transplant marijuana seedlings is vital.

Move them during the plant’s dormant phase (late at night or early in the morning) when the soil is damp. Use a similar medium in the new pot, gently tackle the stem, and water generously to help the roots settle.

What do you add to the soil when transplanting?

Before moving seedlings, you can treat the medium with amendments for healthier growth. Compost, worm castings, and mycorrhizal fungi enrich the soil and boost nutrient consumption. Perlite, peat moss, and coco coir improve water retention, drainage, and aeration.

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