How to Germinate Cannabis Seeds in Rockwool

This is the Blue Dream seed we’ll be planting

Hello everyone, and welcome to another excellent cannabis seeds post. This article will teach you how to start marijuana seeds in rockwool. Planting in rockwool is simple but can seem daunting if you haven't done it before. You want your precious seeds to germinate and grow into big, healthy, bud-filled plants, and we'll take you step-by-step on how to do that.

How to Germinate Cannabis Seeds for Hydroponics

First, I have to confess I love growing cannabis in hydroponics. In my opinion, this is the best way to have an indoor grow setup. There are compelling benefits to growing in a hydroponic setup. Here are my favorites:

• Constant Nutrient access. Growing in hydroponics allows the plant direct access to the nutrients. In addition, the plant shows nutrient excess and deficiencies quicker in hydro than soil, so you can quickly make adjustments.

• Full control over the growing environment.  

• Produces higher yields.  

• Fewer bugs. Soil can be the leading cause of growers getting bugs. Granted that you can get bugs with hydro, but it's much less likely than if you are using soil.   

• Clean. Since you're only using water, spills are easier to clean than if soil dumps all over.  

I've heard people say that hydroponics uses less water. This fact is based on planting in large fields where the entire area is watered. So yes, in that situation, there would be water that is wasted due to runoff and drainage. I'm not sure if this rule applies to people who grow in those soil bags. Let me know your thoughts in the comments.

Read our Hydroponic Cannabis Seeds Guide.

Buy Rockwool Cubes here

Materials you'll need:

• Rockwool Cubes (I like the ones with the hole in them)

• Hydroton

• 5-gallon bucket

• Air pump

• Airstone

• Grow light

• PH tester

• 5.9 PH water

So let's get into how to start cannabis seeds in rockwool.

Germinating Your Cannabis Seed

The first part of growing a cannabis plant is to germinate your seed. We’re going to use Rockwool cubes for this part but there are many other methods to germinate seeds.

Step 1  

Soak your rockwool in 5.5 ph water. I like to let the cube soak for a few hours; this way, it's fully saturated.

Note: Keep the rockwool in the wrapper. This wrapper helps the cube stay moist.

Step 2

Place your seed into the rockwool. Pinch the top of the rockwool closed so your seed is covered.

Using tweezers is helpful to place the seed in the hole.

Hole has been pinched closed

I place my seed on a window sill until I see the sprout start to grow two true leaves and have at least one root sticking out of the bottom of the rockwool. Do not keep the cube soaking in water because this can potentially drown your seed. If you soak the rockwool in advance, there should be enough water in the cube for the seed to germinate and grow its first true leaves without you having to water it.

Two true leaves forming

Roots through bottom of rockwool

---

Getting Your Cannabis Seedling into a Hydroponic System

Step 1

Presoak your hydroton. Hydroton is clay pellets that retain water, perfect for hydroponics. These clay pellets are dusty and need to be rinsed and soaked before use. I use the net pot as a strainer and run water over the pellets until the water runs clear. Then I throw them in a five-gallon bucket to soak for 24 hours.

Hydroton soaking in the bucket. They are so fun to play with in the water!

Step 2

Fill your 5-gallon bucket with 5.9 PH water. You need to ensure that the water level is high enough to reach the rockwool cube and keep it wet.

These buckets are great because they have a tube that shows you the water level.

Close up of water level

Step 3

Pour hydroton into your net pot. Only a small layer of hydroton is needed to get started. We’re going to be placing our rockwool cube in there in a minute.

Step 4

Remove wrapper from rockwool cube.

Step 5

Connect your air pump and airstone and place them in your 5-gallon bucket.

Note: Always use black tubing for this to avoid mold growth.

Step 6

Place the net pot onto your 5-gallon bucket and place the rockwool cube on the bed of hydroton.

Make sure the bottom of your rockwool touches the water. Once the roots start growing into the water, you can lower the water level.

Joining her sisters <3

Step 7

Fill up the rest of the net pot with hydroton. Be careful not to break the stem of the seedling.

Make sure all holes are covered

Step 8

Turn on your grow light, and you're done!  I’m using a small grow tent here but it’s not required to get the seed started.

As your plant gets bigger you'll need to add nutrients to the water to feed your plant.  

Where to Buy Cannabis Seeds

If you need cannabis seeds, we have a ton of strains available in the shop. Our seeds are guaranteed to germinate and are feminized so you won't get any male plants. Click on the link below to be taken to our shop.

how to germinate cannabis seeds in rockwool

We love hearing from our readers. Feel free to leave questions in the comments section below. We are all here to learn and grow together so please keep your comments kind and constructive.

All the best!

The Autoflowering Cannbis Seeds Team