How to Transplant Cannabis Seedlings
Article written by
Homegrown Cannabis Co.American Seed Bank and Cultivation Experts
Content reviewed by
Dr. Lewis JasseyMedical Director - Pediatric Medicine
Transplanting is the process of moving a marijuana plant into a bigger container as it grows. When done to seedlings, it makes space for explosive development during the vegetative stage. Since baby crops are vulnerable, excellent timing and tender care are crucial.
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Why Is Transplanting Important?
Growers typically begin the cultivation journey by planting sprouted cannabis seeds in small pots. This approach makes sense as it ensures that you’re only planting viable seeds and not wasting soil.
Sprouted seeds evolve into cannabis seedlings, develop roots, and soon require more space. At that point, transplanting becomes necessary.
Transplanting cannabis gives the root system space to spread out. Skipping this step leaves you with rootbound plants with tangled and choked bases. It causes stunted growth and reduces the harvest potential.
Effectively, the pot size determines how big your weed plant will get. Cramped spaces stunt it, and oversized ones lead to a waste of water and nutrients. Appropriately-sized containers let the roots get progressively larger and remain healthy.
Most cultivators put germinated seeds in four-inch or one-gallon pots. After several weeks in the seedling stage, crops need to be planted directly into the ground or moved to a larger pot. Otherwise, you may face these symptoms:
- Flimsy growth
- Stem reddening
- Nutrient sensitivities
- Wilted appearance
- Stunted blooming
Oversized containers aren’t optimal, either. Especially when dealing with fragile seedlings, the right transplant timing is everything.
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Signs It’s Time to Transplant Your Seedlings
The right time to transplant seedlings is before they outgrow their current containers. If growing in a solo cup or small container, you primarily rely on above-ground visual cues.
As a rule, move the young plant after 7-10 days if it’s in a Rockwool cube or starter pot of four inches. Those keeping weed in larger containers may wait 3-4 weeks to reduce the shock risk.
In either case, don’t hesitate to transplant if you notice the signs below. If it lasts too long, being rootbound can permanently hinder development.
Here are five telltale signs it’s time to increase the pot size.
1. True Leaves Appearing
Seedlings uncurl from seeds as tiny green stems with round cotyledons on top. As they develop, they start producing true fan leaves with the expected number of blades. When the stem has four or five leaf sets, root growth has reached a point where it needs a more spacious pot.
2. Yellowing and Dying Cotyledons
Cotyledons are precursors to the foliage and remain on the stem for some time after the first leaves emerge. They lose color and fall off as the crop dedicates more attention to its fingered blades.
This development signals the end of the seedling stage and the beginning of proper vegging, which requires bigger pots.
3. Soil Drying Out
When you shower a crop in an appropriately-sized pot, its roots soak in moisture over the next two days. They absorb all available water in a few hours if kept in cramped spaces. The growing medium feels dry after 24 hours or less.
4. Crop Health Issues
Remember the signs of a rootbound plant? They resemble overwatering, nutrient deficiencies, and even poor genetics.
The ideal environment for seedlings is around 75°F, 60-80% relative humidity, and an 18/6 light schedule under fluorescent lamps. The roots may be choking if you’re on top of those conditions and still seeing yellowing, wilting, and drooping.
5. Protruding Roots
The final sign is the most obvious. If kept in cups with drainage holes or Rockwool cubes, plant roots begin protruding from the bottom as they elongate.
How to Transplant Cannabis Seedlings
Now you know why and when, so let’s see how to transplant cannabis seedlings.
Even if your plant is crying out for a bigger pot, take your time to determine the perfect moment for the task. Transplanting has the best results when you:
- Wait until the medium is dry. Wet soil makes the process messier and can fall apart in chunks, pulling on the fragile roots.
- Transplant in the evening. That way, plants get several hours of downtime before performing photosynthesis again.
- Reduce light exposure. If growing indoors, move lamps farther from the canopy for 24 hours. Outdoor cultivators should pick an overcast day or provide shade to crops.
Choose the right timing and follow the steps below for a successful transplant.
Choose a Container Size
It’s time to move your weed seedlings, and you have two options:
- Potting up: gradually increasing the container capacity. Water and nutrients are easier to absorb when the pot isn’t oversized, so this option boosts the growth rate. It also increases the risk of transplant shock, so choose it if you have prior experience.
- Sowing in the final pot: moving seedlings to a container where they’ll finish the flowering stage. They develop more slowly as the roots can’t absorb food and moisture at optimal levels. This alternative works better for autoflower strains and new growers.
If going for the former, use a two-gallon container to move from a one-gallon space. Crops previously in four-inch pots or cups fare best in one-gallon buckets.
In the latter case, pick a three-gallon, five-gallon, or seven-gallon container. The first option is best for autoflowers, the second for most indica strains, and the third for particularly stretchy sativa.
Prepare the Workspace
Seedlings are vulnerable, and transplanting exposes them to adverse environmental factors and pathogens. Cleanliness is key to keeping them safe.
Wipe the surroundings with high-proof alcohol before handling crops to minimize disease risk. Wear gloves or thoroughly wash your hands and ensure the new container is clean.
To prepare for a transplant, sprinkle the stem lightly with water to buffer the plant against strain. Dim the lamps or move your small plants during lights-off hours to reduce stress.
Fill the New Pot
To prepare the receiving pot, get a bag of lightly-fertilized, organic soil from a gardening store. Pour some on the bottom and sides, leaving enough room for the previous container to fit.
Don’t pack the substrate: muddy spots appear, and oxygen doesn’t circulate as freely when the soil is too dense. It’s better to keep it somewhat loose and add more as needed.
Generously soak the medium in the new pot to let the roots make direct contact with moisture right away. Let the runoff collect at the bottom before introducing your seedling.
Move the Cannabis Plant
If you use a solo cup or another disposable container, snip it with scissors and peel the plastic away from the soil. Otherwise, grab the stem just above the ground and gently pull the root ball out.
Immediately move the seedling to the new container. Add another inch or two of topsoil and pat the surface area to make it steady.
Help the Crop Settle
Once the crop is snug in its new home, soak the medium with nutrient-rich water. It’ll spend the next two weeks recovering, so avoid flipping the lights or starting a training technique over this period.
During the next seven days, watch your marijuana for the following symptoms of transplant shock:
- Bronzing on leaf edges
- Drooping and brown leaves
- Wilted foliage dying off
- Slow moisture absorption
- Stunted growth
If you notice these symptoms, trim the dying foliage and never let the root ball dry. You may also supplement the soil with molasses to encourage expansion.
Tips for Future Transplants
If you decide to pot up, you’ll move your cannabis the second, third, and even fourth time to maximize the final yield. When and how should this happen?
Crops are ready for bigger containers when they double in height. They might also display the signs of crowded roots, as we discussed above.
Future transplants look the same as what we’ve described. Pick containers at least double the size of the old ones and perform this process at least a week before blooming. You don’t want to disturb and shock a flowering stage crop.
The Bottom Line
Unless you need compact crops due to space limitations, bigger is better with cannabis plants. Learning to transplant isn’t an advanced technique: it’s something all cultivators should master to get massive, prolific bud-bearers.
Learn the signs of crowded roots and act accordingly. Handle crops carefully to avoid disturbing their root systems, and watch them for signs of shock. Provide proper care to minimize stress and advance your yields.
Now you know the theory. Why not buy seeds, start growing cannabis, and put it into practice?
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