Starting Cannabis Seeds In Rapid Rooters

How to Germinate Marijuana Seeds: 4 Different Methods Plus Expert Tips Okay so I placed my seeds in water until they sank, but I also turned on a heater on the containers to get them hot (no heating pad).. the water got pretty… Rapid Rooters 101: How They Work & Best Alternatives Generally speaking, there are two types of growing media. One kind is loose, sold by weight. For example, perlite, potting mix, peat moss,

How to Germinate Marijuana Seeds: 4 Methods Plus Expert Tips

How to Germinate Marijuana Seeds Method 1: Starter Cubes & Seedling Plugs (Recommended)

One of the best cannabis germination methods is to use specifically-made starter cubes and seedling plugs. These plugs make cannabis germination easy. You simply place the seed in the cube or plug, add water as directed, and seedlings automatically get the perfect conditions for germination.

Each cube or plug already has a hole specifically for you to place your seed. Just stick your seed into the precut hole and pinch the top closed a bit with your fingers. Don’t worry, you can’t mess this part up As long as the seed makes it in there, you should be good.

This is one of the easiest germination methods, and doesn’t leave a lot of room for error. Cannabis seeds and clones can be expensive, and sometimes we have genetics we just can’t afford to lose. When that’s the case, germinate your cannabis with one of the following recommended options to ensure as close to 100% germination rate as possible.

Which Starter Cubes Work Best for Germinating Cannabis?

Rapid Rooters (Highly Recommended For All Setups)

Rapid Rooters are easy to work with – you just stick your cannabis seed in the Rapid Rooter (pointy side down), keep your seed warm and slightly moist, and let the Rapid Rooter do its magic.

Sprouts emerge and roots appear in just a few days.

Rapid rooter starter cubes are suitable for all growing methods, including hydroponics, coco coir and soil. They work for every setup and come from General Hydroponics, a trusted company (the same one used by NASA) which is known for the quality and consistency of its products.

I highly recommend using Rapid Rooters over any other starter plugs. They are less prone to problems and work great with any growing medium (including hydroponic systems).

  • Easy to Use – You Can’t Really Mess Up
  • No Prep or Setup – Open the Package and Go
  • Some of the Best Germination Rates of Any Method
  • Can only get 50+ at a time (General Hydroponics currently does not offer fewer plugs per package)
  • After opening the package, you only have a week or two before they dry out, so if you’re only germinating one or two seeds, you’ll end up having to throw many of the Rapid Rooters away.

There are a few different options for Rapid Rooters, which can be confusing if you’re not sure what you want. The 3 different options for Rapid Rooters are listed here…

Bag of Rapid Rooters

These are round on bottom instead of being a cube, which means they cannot stand up on their own. These are best suited to a hydroponic setup where the Rapid Rooter will be placed directly in the final destination. In our hydroponic setups, we’ve had near 100% germination rates with Rapid Rooters, better than any other seedling cube we’ve tried.

  • Round on bottom (won’t stand up by themselves without support) unless you squish the bottom so it’s flat like this grower did (pic)
  • Great for starting with Rapid Rooter directly in final destination (hydro, soil, coco coir, etc)
  • Get 50 Rapid Rooters at a time
Rapid Rooters Mat
  • Easily break cubes off the mat (already sectioned off with precut holes)
  • Already shaped like cubes with flat bottoms, so they easily stand up by themselves
  • Good for seamlessly transplanting your seedlings somewhere else
  • Get 98 Rapid Rooters at a time
Rapid Rooters Tray

The Rapid Rooters tray is perfect for seeds or clones. Allow your young plants to sit in the tray with water until their roots are well formed and ready to be transplanted to your final destination. The standard size tray fits most humidity domes. You can refill the tray with Rapid Rooters from the bag or mat.

As you can see in the pictures below, the Rapid Rooter Tray comes packaged up. Once you open the package, you will see 50 Rapid Rooters already set in the tray. The resing place for each Rapid Rooter has a hole on the bottom so water within the tray is wicked up. The top part comes apart from the bottom.

  • Perfect for cloning or starting seeds with a humidity dome (standard 10-inch by 20-inch dome like this one – 7-inch height recommended for cannabis seeds or clones)
  • Easy to transplant to new destination
  • Just add water and seeds, that’s it!
  • Whole tray can be refilled with any type of Rapid Rooters (from bag or mat)
  • Comes with 50 Rapid Rooters, ready to go
Germination Station

One option for growers is to use a tool which has been specifically designed to provide optimal germination conditions like this germination station with heat mat.

You can make a DIY germination station at home by putting a plastic dome over a plate of Rapid Rooters on a heating pad.

There are benefits to the professionally made germination stations as they work very well and are pretty cheap to buy.

Rockwool Cubes (Not Recommended)

It’s often hydroponic cannabis growers who use rockwool cubes since these can be safely placed in hydroponic setups, hold a lot of moisture, and are resistant to mold. Rockwool is cheap and easy to find. It comes in convenient cubes. But it does have some major drawbacks…

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Pros of Rockwool

  • Cheap & Easy to Find
  • Inert Medium (useful for hydroponic growers)

Cons of Rockwool

  • Bad for the environment (unnatural material that does not break down)
  • Bad for your health (especially your lungs) – wear gloves and cover your mouth/eyes when handling rockwool
  • Has a pH that is too high for cannabis, so it must be thoroughly rinsed and treated
  • Poor cloning and germination rates
  • Difficult for new growers

Protect yourself! Always use a mask, goggles and gloves when working with rockwool.

If you do use rockwool, it’s recommended you germinate your seeds using another method like the paper towel method, then transplant your seeds to the rockwool cubes after roots have already appeared.

I highly recommend using Rapid Rooters instead for your hydroponic application (or any grow setup), as they are much more user-friendly and tend to get far better germination rates.

Jiffy Pellets

Jiffy Pellets are used in a similar way to rockwool cubes, though these tend to get much better germination results. Jiffy pellets are not suitable for most hydroponic setups where the roots are grown directly in water, but Jiffy Pellets can be directly transferred into soil or coco coir or soil.

  • Good Germination Rates for Soil and Coco Coir
  • Good for Cloning
  • Come in dried pellets, so they can be kept for a long time
  • Not suitable for hydroponic setups
  • Must be soaked to expand each pellet before use

Once the compressed Jiffy pellets have expanded in warm water, gently squeeze excess water from each pellet and you’re ready to go. Treat them the same as Rapid Rooters.

Next: How to Germinate Marijuana Seeds Method 2: Plant marijuana seeds directly in growing medium.

Germinating Seeds in Rapid Rooters

Okay so I placed my seeds in water until they sank, but I also turned on a heater on the containers to get them hot (no heating pad).. the water got pretty hot for about an hour. Could that have been bad for the seed first off/killed them.

The seeds cracked so I placed them in damp paper towel in an enclosed tupperware bin. The tails haven’t showed yet (could they be dead) It has been two days.

I placed them in small rapid rooter plugs (dunked them in 6.0ph water then rang them out) and put a small humidity dome over the top.

Also cut off a small piece of the plug and gently placed over the holes.

They are under 2 23w CFL’s.

Is this going to work?

sativa indica pits
Active Member

yes they might b dead, and no it probably wont work. if there cracked and not sprouted they are dead. next time put the seeds right in the soil in a cup. it is the least amount of stress on the seeds and they usally wont die unless you over water the way to much.

Active Member

Doc, your just going to wait and see. If they don’t come up in a week start over. I’ve always used rooter plugs and almost everything has germed. I soak seeds in the dark for


Rapid Rooters are in truth not ideal for starting seeds, they are too small. When the tap root emerges it immediately wants to grow down several (~2-3) inches. For this reason, and to prevent the media from drying out very quickly, it is recommended to start seeds in a container at least 3.5-4 inches deep. This way the tap root has sufficient room to stretch out from the outset. The seedlings also wont have to be handled so much. You can use Rooters to germ Cannabis seeds, but you’re going to want to transplant them into a larger container relatively soon after they sprout. Right after they sprout you should see a taproot hanging out of the plug, which isn’t really a good thing.

Rooters/plant plugs are awesome for cuttings, but for Cannabis seeds it only seems like a slight step up from paper towels to me.

Finally I have never had to use a dome to germinate Cannabis seeds, and I know at least one of the breeders of a few strains I have grown specifically advise against using a dome, or paper towels. High humidityconstant moisture increases the risk of damping off diseases, various plant pathogens which can kill seedlings and prefer different temperatures. The media just has to be moist for the seed to germinate. Relatively freshhealthy Cannabis seeds (less than a few years old) should germinate easily without the need for soaking.

Active Member

I germinated seeds in a covered mug of water. I placed the mug on top of the cable TV box which gave it a tepid heat boost. I knocked the seeds down and they germinated in a day to a day and a half. When they sprouted a quarter inch of white root, I placed them in the rapid rooters and under my 300W LED light. After a week when they grew tall enough, I put the neoprene disks on them and found the rapid rooters too tall for my 2″ net pots so I pulled and trimmed some of the rapid rooters to fit the into the pots. I had basically destroyed 2 out of nine seedlings but I put them into the net pots and my aeroponic sprayers. They looked really dead for about a week. On one, the short single root started to discolor but I kept them under the lights and the plant started to grow new roots and came back from the dead. I guess they are truly weeds as they survived the trauma.

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Rapid Rooters 101: How They Work & Best Alternatives

Generally speaking, there are two types of growing media.

One kind is loose, sold by weight. For example, perlite, potting mix, peat moss, and compressed clay pellets, fall into this category (read more about growing media).

The other kind of growing medium comes as individual cubes or cylinders. These are called starter plugs. You may be familiar with popular starter plugs like rockwool, Oasis Horticubes, and, of course, Rapid Rooters.

Rapid Rooter is a type of starter plug made by General Hydroponics, beloved by gardeners and hydroponic growers around the world.

Why Use Starter Plugs?

Starter plugs like rockwool and Rapid Rooters are designed to make your growing process easier.

Instead of mixing your own media and packing it into a seed tray, you can pull a Rapid Rooter right out of the package and put your seed into it.

The chemistry required to make a soil-based or soilless mix is taken out of your hands.

And because starter plugs like Rapid Rooters are compact and don’t break apart easily, they can be used directly in certain hydroponic systems, unlike loose media.

What are Rapid Rooters Made Out Of?

Rapid Rooters are made of Sphagnum peat moss and a binder.

Peat moss is a soilless natural product made of decomposed organic matter, mostly Sphagnum moss.

Peat moss is a favorite medium of gardeners around the world because of its great air-to-water ratio.

It’s highly absorbent without compacting easily.

How Do You Use Rapid Rooters?

Using Rapid Rooters is super simple. You can use these starter plugs to start seeds or to propagate clones.

For those of you who don’t know, cloning is the process of growing seedlings from cuttings of adult plants.

To clone a plant, you can remove a branch, pull off the lower leaves, and stick it into a Rapid Rooter or other starter plug.

From there, it will grow into an exact genetic copy of its “mother” plant.

Whether growing from seed or cuttings, the process is similar and incredibly simple.

Here’s how it’s done:

  1. Remove a Rapid Rooter from the bag and rehydrate it in water or a diluted nutrient solution. If your Rapid Rooter already feels moist out of the bag, you can skip this step.
  2. Place your Rapid Rooter(s) into a seed tray.
  3. Place your seed or cutting into the pre-made hole in the top of the Rapid Rooter.
  4. Pour about 16 fluid ounces of water into the tray every two to three days, or as needed.
  5. Place the tray four to six inches under fluorescent or LED lights.
  6. When roots appear, your Rapid Rooters are ready for transplant into your hydroponic system.

Can Rapid Rooters Be Used In Hydroponics Systems? What Else Are They Good For?

Because Rapid Rooters are a soilless starter plug, they can be used directly in most hydroponic systems.

Once your transplant is ready with lots of visible roots woven through the Rapid Rooter plug, you can pop it into a net pot or any growing media that you will be using, including perlite, expanded clay pellets, and even pure nutrient solution for deep water culture and Kratky setups.

In addition to working great for hydroponics, Rapid Rooters can be used in aeroponics or traditional soil-based gardening or farming.

They work just as well in soil as they do in water.

Do Rapid Rooters Need to Be Used With a Grow Tray?

Yes, Rapid Rooters should be used with a grow tray.

Nothing special is required, just any old tray that will fit the Rapid Rooter will do. If you want, you could even use a plastic cup or another small household container.

The reason for this is simply that these starter plugs won’t stand very well on their own—they need some support.

And, they need to sit in something that can retain water. Once you put your seeds in Rapid Rooters and put them into a tray, they should be watered every few days until the seedling has developed.

Do Rapid Rooters Have Nutrients?

No, Rapid Rooters do not contain any significant amount of nutrients.

They are made of peat moss, a soilless organic material. While peat moss is great for retaining moisture and providing plenty of air to the roots, it won’t give your plant the nutrition it needs.

You can, however, soak your Rapid Rooters in a pH-balanced nutrient solution before using them. This will make for even better seedling growth.

Here’s what I recommend:

  1. Take a bucket or container large enough to fit all of the Rapid Rooters you will be using.
  2. Gently place your Rapid Rooters into the container.
  3. Fill the container with just enough water to cover the Rapid Rooters.
  4. Add a small amount of nutrient solution to the bucket.
  5. Add pH-up or pH-down to get to a level that works for the plant you are growing.
  6. Let the plugs soak in the solution for an hour or up to 24 hours.
  7. When you are ready to use your Rapid Rooters, just remove them from the liquid, don’t squeeze them, and then add them to your tray.

Can Rapid Rooters Go Bad?

Yes, Rapid Rooters can potentially go bad.

If not stored properly, mold, fungi, or other pathogens can infect the product. In this case, they should be thrown out.

Another common scenario is that you open up a package of Rapid Rooters only to find that they have gone dry. In this case, they are “bad,” but can easily be fixed.

You can either dip them in some water before using them or follow the instructions above on how to hydrate and add nutrients to them simultaneously.

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Do Rapid Rooters Have to Be Used For Hydroponics?

No, Rapid Rooters can be used for virtually any kind of gardening or farming.

Rapid Rooters are just peat moss starter plugs. General Hydroponics, the company that makes them, manufactures them in a specific way to keep them moist and compact, but other than that, they are a very simple and versatile growing tool.

Rapid Rooters can be used for germinating seeds, cloning plants, or as a growing medium for hydroponics and aeroponics.

Once you have successfully made a seedling with a Rapid Rooter, it can be transplanted into pretty much anything, be it soil, perlite, nutrient solution, or even more peat moss.

Rapid Rooter vs Rockwool

Rapid Rooters and rockwool are both starter plugs used for seed starting and as a growing medium.

They are very similar, but they get the job done in slightly different ways.

For the most part, they can be used interchangeably. Whichever you use comes down to personal preference.

That being said, here are the differences and pros and cons of Rapid Rooters and rockwool.

  • Slightly alkaline pH
  • Not biodegradable
  • Inexpensive
  • Made of rock
  • Good water retention
  • Viable for seed starting, transplanting, and as a growing medium

Rapid Rooters

  • Neutral pH
  • Biodegradable
  • Expensive
  • Made of peat moss
  • Contains trace amounts of nutrients, minerals, and beneficial microorganisms
  • Can retain too much water if you aren’t careful
  • Viable for seed starting, transplanting, and as a growing medium

Rapid Rooter Alternatives

Just like rockwool, there are several great alternatives to Rapid Rooters.

These include Root Riot plugs (very similar), Jiffy Pellets, Oasis Horticubes, Pro-Mix, and a variety of soilless mixes.

Each of these can start seeds and act as a growing medium, they just have slightly different features.

Jiffy-7 Pellets

Jiffy pellets are a name-brand starter plug made of peat moss and/or coco coir.

The growing medium is wrapped in a netting and pre-compressed into discs for packaging. You simply add some water to the disk and it grows like an accordion, up to seven times its size, into a normal-sized starter plug.

Jiffy pellets are extremely similar to Rapid Rooters. They both contain peat moss (sometimes coco coir for Jiffy) bound together. The difference is what they are bound with.

Rapid Rooters are held together with some kind of binding foam that is invisible and biodegradable, whereas Jiffy pellets are bound with a plastic netting that isn’t biodegradable.

So, for example, if you were to plant some Jiffy 7 transplants in your garden, those plastic nets would remain in the soil long after your plant was harvested.

This may be less of a concern in hydroponic systems, but from a sustainability standpoint, it is still a factor.


Rockwool is a wool-like starter plug made out of rocks.

Manufacturers melt special rocks and spin them into the fiber to make this product. Rockwool is used across many industries—commonly as insulation or grow media.

The great thing about rockwool is how affordable it is. Compared to some of these name-brand products, rockwool can get the same job done and save you some money.

However, rockwool is not biodegradable and you will need to pH-balance is, as it has a pH of around 8, which is too high for your plants.

Oasis Horticubes

Oasis Horticubes are synthetic foam-like starter plugs. This is a name-brand product, specially engineered for hydroponic seed germination.

The foam doesn’t hold much water but drains incredibly well, making it ideal for constant or drip watering systems, like nutrient film technique (NFT), Dutch buckets, or deep water culture.

Also, the foam doesn’t compress, so even after constant waterings, aeration and drainage will remain the same.

The downside with Oasis Horticubes is that they are more expensive than something like rockwool and are much less versatile.

Because they don’t retain water well, Oasis Horticubes aren’t ideal for hydroponic methods that don’t irrigate frequently, if not, constantly.


Pro-Mix is a type of loose, soilless mix.

This isn’t a starter plug, but it can be used similarly. Just take the same tray you would normally use for plugs and fill the cells with Pro-Mix.

Pro-Mix offers a variety of products for different growing applications.

All of the products are peat moss-based and contain beneficial substances to help your seed germinate and grow.

The mix contains biostimulants, which are chemicals or microorganisms that help the plant take in nutrients more efficiently or increase crop quality, as well as mycorrhizae, or beneficial fungi.

While this is a great product, it can be quite expensive and lacks the convenience of preformed starter plugs like Rapid Rooters and rockwool.

Soilless Mixes

Lastly, we have soilless mixes. This is a general term for any loose hydroponic media that may resemble soil but actually contains none (like this one by Fox Farm).

Popular soilless mixes include coco coir, peat moss, perlite, vermiculite, sand, rice hulls, and more.

These growing media can be mixed and combined to provide whatever level of water retention, aeration, and price you desire.

If you care to tweak and refine your own mix, soilless mixes are great as they give you nearly endless customizability.

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