Posted on

planting cannabis seeds in rockwool

Planting cannabis seeds in rockwool
Seeds need air and water to germinate, if there’s too much of one, the other falls short, preventing germination.

Best Way To Germinate Weed Seeds

You’ve probably noticed by now that there are a few different methods you can choose to germinate your cannabis seeds.

Not all of these methods have the same success rate, and your precious cannabis seeds are expensive to buy.

Therefore, you really want to choose the germination method that’s going to give your seeds the best chance to become beautiful, bud producing plants.

So what is the best way to germinate weed seeds? Read on to find out…

Related posts from GreenBudGuru

Best Way To Germinate Weed Seeds

First, take a look at the comparison table below to get an idea of some general success rates for each germination method.

We’ll explore each method in more detail below.

Germination Method Success Rating
1. Starter plugs & Seedling Cubes 5/5
2. Planting directly into soil 3/5
3. Soaking seeds in water 4/5
4. Paper towel method 3/5

1. Starter Cubes & Seedling Plugs

This is by far the best method to germinate weed seeds.

Germinating with starter plugs or cubes is easy and the most reliable method on this list.

What Plugs Should You Use?

Options for starter cubes are seemingly endless, but the majority are made of either rockwool or peat.

The differences are subtle, but very important depending on how you plan to grow your plants after germination.

Peat plugs are an organic option, and sometimes contain a small starter nutrient charge which helps young seedlings after germination.

Rockwool cubes, composed of fibrous wool-like material provide great water and air exchange, which is ideal in hydroponics.

Peat plugs hold more water than air compared to rockwool cubes, so they aren’t ideal for hydroponic grows.

So, rockwool or peat? The primary difference comes down to how you will grow the plant after germination.

For hydroponics, rockwool is the better choice.

For soil/coco/etc., peat plugs generally fare better, but ultimately germination will be nearly identical for these two germination mediums.

How To Germinate With Plugs:

Step 1: After buying your plugs or cubes, soak them in water until they are fully saturated.

Step 2: Place your seed(s) into the pre-cut holes in the plugs. Use some of the plug material to gently cover the opening.

Step 3: Put the plugs into a square box or tray and cover with a plastic dome. This ensures a high humidity environment, which increases germination success, and helps seedlings along after germination.

2. Planting Directly Into Soil

This method is as old-school as it gets, drop your seeds in some dirt, add water, and you’re done.

If only it were that easy!

Unfortunately, it’s not quite so simple.

There are lots of factors that go into this method, and each must be nearly perfect for germination to occur.

How to germinate seeds directly in soil:

Step 1: Purchase quality soil from a reputable source. You want soil with good drainage, this allows for air exchange; seeds need moisture but you don’t want to drown them.

Step 2: Now, you need to plant your seeds at the right depth. A good rule of thumb is to plant seeds 2 times deeper than the width of the seed.

Step 3: Provide water for your seeds by soaking your container in a tray containing about an inch of water. This allows the soil to be moistened uniformly, preventing over-watering. This also keeps the seed in the perfect place for germination to occur.

Check out this method in action:

This method allows you to start your seed directly in your planting medium, but if you aren’t careful with this technique, you can run into trouble.

Seeds need air and water to germinate, if there’s too much of one, the other falls short, preventing germination.

If planted too deep, the energy available to the seedling won’t be enough for it to break the surface.

This will essentially starve and kill your seedling.

If you don’t plant deep enough, the seedling may dry out, or never become moist enough to germinate.

3. Soaking Seeds in Water

This method is not so much a way to fully germinate your seeds, but rather ensures rapid and reliable germination.

As mentioned in the previous methods, seeds need water to germinate.

This method involves placing seeds in a container filled with water rather than into a plug or the soil.

How to start germination with water:

Step 1: Place your seeds in a container of clean water and allow to soak overnight, or for at least 12 hours.

Step 2: After soaking at least 12 hours, use sterilized tweezers or clean hands to remove the seeds. Immediately place the seeds into your medium, such as a plug or soil.

Check out this method in action:

Why does this work?

This method increases germination rates because the seed is primed, it’s already absorbed water and broken dormancy, so is ready to push out it’s first roots.

4. Paper Towel Method

The paper towel method is similar to soaking seeds in water, but this method will germinate your seeds to the point where the taproot has emerged.

How to germinate seeds with paper towels:

Step 1: Place a folded wet paper towel into a plastic container, or on a plate.

Step 2: Place your seeds on the paper towel with adequate space between them. Cover the seeds with another folded wet paper towel.

Step 3: Put a lid or plastic wrap on the container, or another plate on the plate. Seal the container but leave a small hole for air exchange.

Step 4: Place your plates or container in a warm (70-80F / 21-26C) and dark environment

Like soaking the seeds in water, this method provides lots of water to the seeds to start germination.

But it also allows enough air exchange for the seed to produce a taproot and begin growing into a seedling.

Check out this method in action:

This method helps to increase the chances of germination and seedling success, but can introduce some extra issues.

  • Once seeds have germinated, they may grow into the paper towel, making removal difficult and potentially damaging the fragile seedlings.
  • The paper towels and the container you use for germination must be sterile. This is nearly impossible, so you are likely to grow more than seedlings (i.e. fungus) with this method.
  • The extra handling of sprouted seedlings is the biggest issue with this method. Even if you’re very clean and careful with your seedlings, it is extremely easy to damage or contaminate them. Contamination and early damage can ultimately stunt or kill your baby plants.

Verdict

So what is the best way to germinate weed seeds?

After examining each method, if you absolutely had to pick one, it would be starter cubes and seedling plugs.

If you consider everything that can go wrong when germinating seeds, this method does the most to remove potential pitfalls.

Why Plugs?

  • It’s relatively fool-proof because the cubes can only hold so much water, so no overwatering.
  • The pre-drilled holes are not too deep or too shallow for cannabis seeds.
  • The cubes/plugs hold moisture for long enough time to allow for the seeds to take up water. They also won’t dry out too quickly.
  • They provide a soft medium for young roots to push through.

But the best way to germinate weed seeds would really be a combination of these methods.

Use either the paper towel or water soaking method to get your seeds to uptake water.

Next, transition them to either soil or plugs.

This gives you the advantages of each method, with the least downside of each.

Germination Tips

Here are a few extra tips to follow when trying to germinate your cannabis seeds:

  • Keep temperatures in the area you are germinating seeds between 70-80F (21-26C)
  • Germinate seeds in total darkness
  • Don’t use hard tap water (ppm above 120), it can damage the seed
  • Avoid using chlorinated tap water, it can damage or kill microbes that help young seedlings develop
  • Don’t add nutrients to the water when germinating seeds, the seeds already contain all the nutrients they need
  • When seeds germinate, don’t put them under intense light (HID or sunlight), the seedlings will burn and/or dry out
  • Provide non-intense light (i.e. T-5 fluorescent light) for seedlings as soon as they emerge, this will prevent stretching

Related posts from GreenBudGuru

Planting cannabis seeds in rockwool
Avoid compressing the rockwool cube after soaking in water in step 1. You want to keep the fibers loose to allow the roots to easily penetrate them.

Weed seeds in rockwool: how to grow marijuana seeds in rockwool cubes

It’s easy to learn how to grow marijuana seeds in rockwool cubes in a few simple steps. Here’s how you do it.

Growing marijuana seeds in rockwool cubes is an easy and effective way to propagate cannabis seeds. Rockwool is a reliable growing medium for pot seeds, and it’s suitable for all types of growing including hydroponics and coco coir.

In this post we’ll show you how to germinate a weed seed in a rockwool cube. We’ll discuss how to prepare the cubes, proper watering (watch that PH!), proper lighting, and how long your seed will take to sprout (usually within a few days).

How to germinate weed seeds in rockwool cubes:

  1. Soak rockwool cube in one pint of water that is PH’d down to 5.5 (no extensive soaking is required). Include 2ml Canna Rhizotonic per pint (or use a similar rooting product) to encourage root growth.
  2. Remove from water and shake gently to release excess water.
  3. Add marijuana seed to the hole in the rockwool and push to the bottom gently with a toothpick.
  4. Place under a light in a hum >Most rockwool cubes made for growing marijuana seeds come with a hole in them.

Preparing your rockwool cube is fairly easy. Most rockwool cubes made for seed propogation have tiny holes in them. If yours doesn’t, bore one out by gently twisting a wooden skewer about 3/4 down. You want your seed to sit in the bottom of the hole.

Your next step is to soak the cube in a light nutrient solution. I like to use Canna Rhizotonic to stimulate rooting, it’s worked well. I’ll also add a very light mix of Canna Coco A & B, the same nute line I will run once the seeds grow roots. If using tap water let it sit out 24 hours so the chlorine can dissipate (you can use an air stone to speed up this process).

Since rockwool cubes have a very high PH, you need to offset this by lowering the PH of your watering solution to offset it. This is the most critical part of growing pot seeds in rockwool.

What is the proper PH when watering rockwool cubes for cannabis seeds?

The proper PH for watering rockwool cubes when trying to germinate cannabis seeds is 5.5. Try to keep the PH of your nutrient solution as close to that as you can. Use PH down (or substitute lemon or lime juice) to lower the PH once you’ve added your nutrients.

If mixing a small amount of nutrient solution, use a dropper to apply one drop at a time. Mix gently and test with a PH meter. If you go too far, add a drop of PH up until you hit the 5.5 mark.

Soak your cube in the 5.5 PH nutrient solution for 15 minutes – overnight. Remove from the water, gently shake. Now you’re ready to add your seed.

Where should weed seed be placed in rockwool cube?

The marijuana seed needs to sit in the bottom of the hole in your rockwool cube. Drop seed in hold and very gently push down with a toothpick or wooden skewer. Be gentle!

How long does a marijuana seed take to grow in rockwool?

Marijuana seeds grown in rockwool cubes usually germinate within a few days. If they still haven’t germinated after a week under proper lighting, watering, and humidity conditions then your seed might be a dud.

Some growers use 2 seeds per rockwool cube, letting each sprout for a few days. They’ll then thin out the weaker seed by snipping it’s stem at the base of the cube (don’t pull out, it may damage the other seed’s roots). The benefit is that the grower is left with the strongest, most robust plants.This method is great if you have a lot of seeds, but for the average small home garden it might be a bit wasteful.

What type of lighting should be used?

Seeds like warm temperatures. Using a clear plastic humidity dome provides an optimal environment. I use a large CFL lighting fixture designed for growing seeds and clones. You can also use flourescent tube lights, LEDs, low wattage HID lighting, or even a sunny window. Avoid high-powered HID lighting such as 1000W Metal Halide or High Pressure Sodium lights, they are too intense for young seedlings.

Tips for germinating marijuana seeds in rockwool

Rockwool is very alkaline so you need to go 5.5 with the PH to balance it out. You’ll notice a few leaves emerge and will start to see roots poking out the sides. At this point your marijuana seed has sucessfully rooted in the rockwool cube. Monitor the rockwool for dryness, and water with additional PH 5.5 water, Rhizotonic, and a very light nutrient mix when needed.

Avoid compressing the rockwool cube after soaking in water in step 1. You want to keep the fibers loose to allow the roots to easily penetrate them.

Make sure to monitor your rooted weed seeds closely. Look for signs of nutrient deficiencies in the new leaves, which could be due to either too light nutrient mix or potentially nutrient lockout caused by improper PH. PH issues can be addressed by soaking the cube in 1 pint PH 5.5 water with light nutrients and Rhizotonic. Adding the plant to the permanent medium will allow you to introduce a properly PH balanced environment for the roots to expand outside of the rockwool cube.

When should a weed seedling be transplanted from a rockwool cube?

As your new marijuana plant sprouts from the rockwool cube it will begin growing roots. These roots will begin to poke out of the sides of the cube soon after the seedling emerges. At this point it is ready to transplant.

One advantage to growing weed seeds in rockwool is that they can be easily transplanted across most common growing mediums, such as soil, coco coir, and hydro methods such as Deep Water Culture (DWC). If you’re growing in coco you can learn how to transplant seeds in coco coir here.

What is rockwool?

Rockwool is made by melting a mixture of Chalk, rock, and sand at very high temperatures. Air is blown through the molten mixture similar to making cotton candy, resulting in a mineral wool with long fibers that are capable of holding a lot of liquid. This makes rockwool a great medium for germinating cannabis seeds and growing hydroponically.

Rockwool is a man-made substance and it doesn’t break down, so it’s not the best for the environment. Avoid breaking up the cubes and breathing in the small fibers, they’ll damage your lungs.

Summary

Growing weed seeds in rockwool cubes is an easy way to start your cannabis plants. Marijuana seeds typically germinate within a few days in rockwool cubes. It’s important to properly pH the nutrient solution to 5.5 to balance out the higher pH of the rockwool, this provides the slightly acidic conditions that marijuana thrives in.

My weed seeds rooted in rockwool – what next?

Once your weed seeds have rooted in your rockwool cube you’re ready to plant them permanently. Learn how to choose the best growing medium for your weed plants.

If you’re new to growing and are looking for an easy medium to grow in, consider using coco coir. It provides the quick, robust growth of hydroponics but while being somewhat forgiving.