How And When To Transplant Cannabis Seedlings
The seedling phase is arguably the most important of the entire cannabis life cycle. Whether you grow from seed or clone, the hands-on part of cultivation begins with seedlings. Transplanting is all important. Get it wrong, and the crop could be lost. Get it right, and grow great ganja with this guide.
THE IMPORTANCE OF CARING FOR CANNABIS SEEDLINGS
Post-germination or post-cutting, your bean or sprout needs a place to take root. The prime objective for the cannabis plant during the seedling stage is the development of a healthy root zone. If your seedlings struggle now, it’s likely they may never completely recover, and even more likely they won’t reach their full potential. Worst case scenario, seedlings die off and the grow is over before it’s even started.
THE OPTIMAL CONDITIONS FOR SEEDLINGS
Cannabis seedlings need to be treated delicately. Mind your marijuana like babies. If seedlings need support, prop them up with a toothpick or a cocktail stick and some soft gardening wire.
An 18-6 light schedule is considered the sweet spot by most growers. White light is preferred. The source of light should be CFL, MH, or LED. If you have a sunny windowsill, it can work in a pinch.
Roots grow in the dark. That’s why we advocate 18-6 or 20-4 over a nonstop 24-hour light cycle. High humidity, ideally around 70% RH, and temperatures in the 20–24°C range make for a perfect seedling habitat. A propagator, thermo-hygrometer, and a spray bottle of water are the tools to help you dial it in.
Stretchy or floppy seedling growth can be due to genetics. Often, it’s an indication the grow lamp is positioned too far away from the canopy. A cool white 250W CFL can comfortably hang 15cm above a dozen or more seedlings without scorching leaves.
WHAT’S THE BEST STARTER SUBSTRATE?
The medium must be wet, not waterlogged. An effective wet-dry cycle is the goal. Remember to resist the temptation to overwater. Better to mist plants with a sprayer if you are not sure. Touch the medium to feel how dry it is and keep RH high.
Before we go into the specifics, we need to be clear that starting in one medium and switching to another can be hazardous. Keep it simple and keep it consistent. You can’t start seedlings in soil and transplant later into a DWC bucket.
CUBES, CUPS, AND SMALL CONTAINERS
Rockwool cubes and blocks are made for hydroponic growers. Start your seedling in a small cube and it couldn’t be easier to transplant later. Simply cut a cube-sized chunk out of a larger block and insert. The process can be repeated with minimal stress to plants.
Unfortunately, rockwool is a really bad idea for soil growers, even the smaller sized blocks. Invariably, the block retains more water than the surrounding soil. Green, sludge-like algae growth soon becomes a problem. Sure, sometimes you can get away with the tiny cubes, but why take the risk?
An oxygen-rich medium that drains well is the ideal mix for soil and/or coco growers. Between these two growing styles, there is the most overlap during the seedling stage. Peat or coco cubes are easy to use and relatively inexpensive. Similar to a rockwool block, you can visually monitor root development as the white spaghetti strands protrude from the cube. Growers, both organic and hydro, working with clones report the highest success rates using the cube-sized starter mediums.
Many soil and coco growers use cups or small plastic pots as starter containers, typically, anywhere in size from 0.5–5l. Lightly fertilised soil mixed with perlite or coco coir mixed with 30–50% perlite are the most common blended media for seedlings. So long as the base of the container has plenty of drainage holes and the interior can hold the volume of medium required, it can serve as a starter pot. Don’t be afraid to improvise. Poke a few holes in the base of a paper coffee cup with a pin and it becomes a pot.
WHEN TO TRANSPLANT SEEDLINGS
The right time to transplant your seedlings is just before they outgrow their current container. With cubes, you can see roots poking out telling you it’s time to pot up. When you start with a cup or small pot, you are relying on above-ground cues. Typically, when the set or sets of true leaves of the seedling have spread out to cover the circumference of the container, it’s time. Also, vertical growth will be an obvious indicator.
Don’t wait too long to transplant. Rootbound plants will take time to recover and may be permanently stunted. In general, it takes 7–10 days for a seedling to take root and outgrow small starter pots of 1l or less.
HOW TO TRANSPLANT SEEDLINGS
Cubes are the easiest to work with. Either cut a hole to size in a bigger block, or burrow a hole into the medium with your fingers and insert for a snug fit. Potting up takes a little more finesse. First, don’t fill your large container all the way to the top. Leave room so you can water properly later. If you pack the pot all the way to the top, water will mostly run off and not reach the roots.
Next, make an impression in your large container with another small pot, or the one with the plant in it if you don’t have any others. Make this impression in the medium after you have watered it. This creates a perfect imprint for the transplant.
It’s best to wait until the medium in the small pot is dry before going for a transplant. Wet soil can fall apart in chunks as you fumble with the sopping mud. Now, turn the dry plant upside down, and firmly pat the bottom. Grasp the plant stem from the base and ease the compacted medium out of the container in one piece. Some topsoil will spill, but don’t worry.
Finally, gently slide the plant, roots first, into the large container. Replace the lost topsoil or coco with a handful or two over the top and add a little more water. That’s the secret to stress-free transplanting.
POTTING UP VS BEGINNING WITH BIG POTS
If your final container size is up to 11l, you have the option to sow seeds directly. This is only a viable option when growing from seed. Clones will not take root in such a large container. Initially, seedlings in large pots will grow more slowly than those in smaller containers. After a few weeks of vegetative growth, the difference is negligible.
If you don’t transplant, then you eliminate the risk of transplant shock. But you also limit the potential of your cannabis plants. That being said, a first and final transplant is sometimes the best option for autoflowering strains with a short life cycle.
Unless smaller plants are advantageous due to limited grow space, bigger is always better. Transplanting is not something beginner growers should avoid. The only way to learn is by doing. If you ever want to grow marijuana monsters, you need to master transplanting seedlings.
Transplanting seedlings is a critical stage in the cannabis life cycle. Get your grow off to a great start with our guide to transplanting.
How to Germinate & Transplant Cannabis Seedlings
Marijuana Seedling Germination & Transplant Guide
In this tutorial, you’ll learn how (and when) to transplant your new cannabis seedlings so they grow as fast as possible!
Did you know that seedlings in solo cups often grow faster than seedlings started in big containers?
The reason some growers transplant their plants instead of starting them in their final container is that seedlings usually grow faster during the first few weeks of their life if you start them in something small like a solo cup. The growing medium dries out much faster in a smaller container, which means your seedling roots are always getting access to lots of oxygen at all times. It also makes it more difficult to overwater your plants!
If you start seedlings in a solo cup, you should try to transplant to a bigger pot around the time the leaves reach the edges of the cup. This seedling is ready for transfer!
If seedlings get too big for their cups before transplanting to a bigger container, you may accidentally limit your plant’s root space. This slows down growth and can cause puzzling deficiencies! So if you do start in small containers it’s important to transplant your seedlings on time to avoid letting them become rootbound!
“Rootbound” seedlings are often droopy and may display odd symptoms that are hard to explain. If seedlings are rootbound you’ll see during the transfer process that the roots have wrapped all the way around the outsides of the container, preventing the plant roots from doing what they need to do. Try to transfer to a bigger pot before this point!
For many growers, it’s simpler to start plants in their final containers. Although your seedlings may grow slightly slower at first, you never have to worry about transplanting them. You also avoid the possibility of shocking them during the transplant process.
That being said, if you want the fastest growth from your seedlings and don’t mind transplanting, starting in small containers like solo cups may be the way to go.
The truth is, your seedlings will thrive whether you start in a big or small container as long as you take good care of them! Neither way is the “best” method; it’s more a matter of personal preference.
How to Transplant Seedlings
1.) Germinate Seeds with Paper Towel Method
Before you can start transplanting, you need to germinate your seeds. I recommend the “paper towel” method for germination because this method is easy and hard to mess up! Learn About Other Ways to Germinate Seeds!
- Place your seeds inside a folded wet paper towel, and place it between two paper plates (or regular plates) so that they don’t dry out.
- Check on your seeds every 12 hours but try not to disturb them. When they’ve germinated, you’ll see the seeds have cracked and there are little white roots coming out.
- They should germinate in 1-4 days, though some seeds can take a week or longer (especially older seeds).
- Keep them warm if possible. One thing you can do to get seeds to germinate a little faster is to keep them in a warm place (75-80°F). Some people use a seedling heat mat but in most cases that’s unnecessary.
These seedlings were sprouted using the paper towel method!
Once your seeds have germinated, gently plant seeds in a solo cup about an inch deep, roots down.
Make sure to cut plenty of holes in the bottom of the solo cup first, so water can drain out the bottom easily!
Add your potting mix to the solo cup. Dig a small hole about 1-2″ deep and gently place your sprouted seed, root down, into the hole you made. Lightly fill around and cover with soil. You’ll see a seedling emerge a day or two later!
Here’s a quick cheat sheet for the paper towel germination method!
2.) Allow leaves to grow to edges of the solo cup
Your seedlings will take off in a day or two, and soon it’ll seem like they’re growing more and more each day!
Once your seedlings have grown enough that their leaves have reached the edges of the solo cup, it’s time to transplant to a bigger container!
These seedlings are begging to be transplanted to bigger pots (especially that big one on the bottom!)
Transferring to a bigger container at this stage will prevent your seedling roots from becoming rootbound and “choking” themselves because they get all wrapped around the outside of the soil. The outside circling of the roots prevents the plant from using water and nutrients properly, so you often end up with droopy seedlings and hard-to-explain nutrient deficiencies.
3.) Transplant seedlings to a 1, 2 or 3-gallon pot (then to an even bigger final container if you desire)
Instead of pulling the whole plant out of the container, sometimes you can just cut away the solo cup when you plan on transplanting. This is one of the advantages of starting in disposable cups – it makes transplanting easy and stress-free. You can also gently run a butter knife around the outside to help loosen the soil, turn it upside down and pat out the seedling, soil and all!
Transfer seedling into a new container by digging a hole the size of a solo cup, and gently placing your seedling in the new hole without disturbing the roots at all if possible, like this!
How to Avoid Transplant Shock
The process of transplanting from one container into a bigger one can shock your cannabis plants, especially if you wait too long to transplant.
You don’t want cannabis transplant shock!
You can help avoid causing your cannabis plants stress during transplant by following these principles:
- Transplant your cannabis plants after their roots have begun to fill container (to help hold all the growing medium together) but before the roots have started wrapping around the edges (plants have become rootbound).
- Water your cannabis plants 1-2 days before transplanting. This will help the growing medium stay together (since it’s moist), but still slide out easily (since it’s not soaking wet).
- It’s better to transfer too early than too late!
- If the roots haven’t grown all around the sides of the root ball (plant isn’t rootbound), avoid disturbing the roots if possible. There’s no need to shake out dirt, just carefully move entire root ball directly into the next pot.
- Make sure your plants are in their final container at least 1-2 weeks before you switch them over to the flowering stage, and avoid transplanting plants during the flowering/budding stage if you can since the stress may affect your final yields.
- If your cannabis plants seem like they are suffering from transplant shock (leaf symptoms, drooping, slowed growth), it can be helpful to use a seaweed kelp extract (often available as a liquid fertilizer) to help your cannabis recover more quickly.
- If transplanting seems scary, it’s okay to plant your seed or clone in its final destination right at the beginning, just be wary of overwatering until the plant has a few sets of leaves and is growing vigorously. You can increase the amount of oxygen available to your plants by adding extra perlite to loosen the soil and allow water to drain through more easily.
- Water your cannabis properly after they’ve been transplanted for the best results!
If you follow all these steps, you may notice that your plant doesn’t show any signs of stress at all!
Now you just allow plants to grow!
4.) Transplant to an even bigger container if desired
If your cannabis plants double in height while still in the vegetative stage, you may want to consider transplanting them into an even bigger container for the best results. The final size of your cannabis plant is constrained by the pot size. If you keep your plants in small pots, they simply won’t grow as big as they would in bigger pots.
If you’re trying to keep plants small, small containers can actually be a good thing. But if you want to grow bigger plants, you need to give their roots enough space to “spread out” 🙂
What Size Final Container?
A general guide is to have at least 2 gallons per 12″ of height. This isn’t perfect since plants often grow differently, and some plants are short and wide instead of tall, but this is a good starting rule of thumb.
So if your final (desired) plant size is…
2-3 gallon container
4-6 gallon container
6-8 gallon container
8-10 gallon container
10+ gallon container
Go Bigger If You Need to Spend Time Away From Your Cannabis!
If you plan on being away from your plants for more than a day or two during the grow, it can’t hurt to go up a size or two. The bigger the container, the less often you need to water. So even if you get slightly slower growth in a too-big container, you will definitely be able to spend more time away from your plants without having to water them!
5.) You’re Done!
That’s it. You’re done transplanting your weed plants!
Now you just need to worry about taking care of your plants until you’re ready to start flowering/budding. Remember plants will usually double (or even triple) in size from when you first initiate the flowering stage!
Note: You can skip transplanting if it seems like too much work for you. Just make sure you’re careful not to overwater small plants in too-big containers. Once plants start growing vigorously, you don’t need to worry as much about overwatering. Learn more about common seedling problems.
Should I start in a solo cup or in a bigger pot?
I think it’s a matter of preference. Just as a quick summary: It’s easy to give too much or too little water to a very small seedling in a big pot. With a solo cup, you just soak the grow medium and the roots get a lot of both oxygen and water at all times because the medium dries out quickly. The downside is you have to transplant a seedling as soon as the leaves reach the edges of the cup, or its growth starts slowing down. Also, if you’re not careful you could possibly shock the plant during transplant.
Seedlings started in solo cups take less room in the grow space, and tend to grow a little faster! But if you’re careful about watering plant in a big container, you can get seedlings to grow almost as fast without having to worry about transplanting.
I’ve done it both ways and each method will serve you well. In the end, don’t stress too much. Your seedlings will come out fine as long as you pay attention to them 🙂
Learn how to germinate and when to transplant your seedlings so you get the fastest growth. This step-by-step tutorial includes pictures plus hints and tips!