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Germinating Cannabis Seeds for Hydroponics Systems

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Added 07 December 2021

There are many ways to kickstart cannabis seed germination, but not all of them suit your hydroponic system. So, you have to choose a germinating process suitable for hydroponic cannabis plants. 

When growing in soil, all you have to do is stick the seeds in the soil, but you’ll have to do things a little differently in hydroponic setups. 

In this article, we show you the best and easiest ways of germinating cannabis seeds for hydroponics.

Things You Need to Start Seeds in a Hydroponics System

Before getting started, you must provide the right environment for cannabis seeds to sprout. In simple terms, you’ll mimic Mother Nature and hope that the plants are happy. 

In a natural environment, cannabis seeds sprout best in spring. So, it makes sense to mimic the spring environment to germinate the seeds for your hydroponic culture.

You need some growing media, moisture, nutrients, light, and mildly warm temperatures of around 18°C-20°C. Cannabis is an easy plant to grow, so you don’t need to invest much, except for a few essential pieces of equipment.

Germinating Cannabis Seeds for Hydroponics

Typically, growers simply place the seed in a little bit of soil and water it until the seed sprouts. But this germinating method is not suitable for hydroponics. So, instead, you can these three methods below to sprout your seeds — they are easy and effective! 

Germinating seeds in water

The easiest and most basic method is the water method, and you can expect at least 90% germination rates. 

Seeds in water

To start, place your cannabis seeds in a glass of fresh water, away from light, and wait for them to sprout.

Usually, the seeds sprout within 48 hours, but older ones may take up to a week to pop. 

Once the taproot shows, you can start planting the seeds. However, be careful not to touch the taproot while transferring the seeds to your hydroponics system, as they are pretty fragile.

Germinating seeds in a paper towel

Time to go back to high school days with fun biology experiments!

The paper towel method is a true classic used by growers for generations, and it’s quite simple (and fun) to do. But, most importantly, it helps you maintain the perfect environment for your cannabis seeds to germinate.

Seeds in paper towel

Place your seeds on a clean paper towel, fold the towel over the seeds, and spray clean water over the towel. You only need to splash enough water to moisten the paper but do not soak it completely, or the seeds will rot and die.

Maintain moisture

After that, place the damp paper towel on a plate and cover it with another plate or lid to keep the seeds away from light and retain moisture.

You can also modify the method using two cotton pads instead of the paper towel if you’re afraid the sprout will stick to the towel fibers. Or, you can place the towel or cotton pads in an airtight container or ziplock bag instead of plates.

Transfer the seeds

Wait for a couple of days until the taproots show up. You can then move the seeds to a medium of your choice. It’s okay to use coco coir or peat for a few days until the cotyledons or first couple of leaves pop up. Or, you can use jiffy pellets that work just like coco coir. Again, avoid touching the taproots while transferring the seedlings to your hydroponics system. 

Germinating in Rockwool or starter cubes

The two methods described above are classics, but you can also take the modern route of using Rockwool or starter cubes for germinating cannabis seeds for hydroponics.

Rockwool is inert and easy to find, and it’s made from volcanic rock and other minerals like limestone or basalt. Growers choose this for its mold-resistant and moisture-retention qualities.

However, Rockwool has some drawbacks — it has a pH of 7.0 that is too high for cannabis. An ideal pH for cannabis is 5.5 to 6.5.

Rockwool cubes

So, if you are using Rockwool cubes, start by soaking the cubes overnight in pH-balanced water and rinse them thoroughly the following day.

Poke holes and insert seeds

Then, poke a small hole in the Rockwool cube using a toothpick and insert the seeds. We recommend using gloves and masks while using Rockwool cubes as the tiny fibers aren’t good for your health.

On the other hand, you can also use start cubes (not peat pellets) as they don’t require any pH balancing. So, first, soak the starter cubes in water overnight, and the following day, place a seed in each cube.

Place in grow tray

Once you’ve placed the seeds into the Rockwool or starter cubes, you can place the cubes on the grow tray. Next, fill the bottom of the grow tray with an inch of clear water or a mild nutrient solution.

Use the heater or heating mats to maintain a 20°C-30°C temperature and 80-90% humidity level. And finally, keep the lid on to mimic a greenhouse effect for your cannabis plant. You will see the seeds sprouting in a couple of days.

Notes to remember on germinating cannabis seeds hydroponically:

If you have done everything right, things will go well. However, the seeds may not sprout at times or may not grow well despite germinating quickly. Sometimes, the seeds may not be viable and may not germinate even if you do everything right. 

Therefore, it is essential to purchasing seeds only from reputed breeders. If the seeds are good, though, you may need to consider a few factors, including:

  1. Moisture ‒ Although plants grow in water in hydroponic systems, new seedlings do not appreciate wet feet. The secret is to maintain appropriate moisture levels that should be damp — neither wet nor dry. Seeds that are wet for far too long will either not germinate or take a long time to grow. Eventually, newly germinated seedlings will collapse and die because of excessive moisture. To check the moisture levels, squeeze the growing media slightly — if it drips water almost immediately, it's too wet for the plants. Simply squeeze out excess water in such cases. On the other hand, if there isn't water at all, then the media is just too dry for your seeds and seedlings. Add a few drops of water to your growing media in such cases.

  2. Temperature ‒ Hydroponic plants tend to grow best when you maintain appropriate temperatures. The temperature must not be too hot or too cold but just right for the plants to thrive. Maintain stable temperatures between 73°F-83°F at all times. You can use a humidity dome for the first few weeks to maintain the right temperatures. If not, invest in an air conditioner to make sure the temperature is stable at all times.

  3. Light ‒ Some growers tend to use lights as soon as they stick seeds in the growing media, but it's unnecessary. Other growers use powerful lights on the very first day. While it's okay to use soft lighting, powerful lights can kill the seedlings. On the other hand, the seedlings may die if they are kept in complete darkness for more than 24 hours.

  4. Handling ‒ Seedlings are incredibly fragile, so make sure you handle them as gently as possible. Do not touch the taproots as the seeds germinate. Unfortunately, many inexperienced growers touch the seeds frequently as they sit in the water, reducing germination rates.

  5. Reservoir ‒ Once you prepare the nutrient solution in the reservoir, just ignore it for a few days when the seedlings are young because they don't respond to sudden changes in the reservoir very well. But, if you have no choice other than to change the water, just top the solution with a new solution until the plant is 2-3 weeks old. The only factor that matters is the pH, so if the pH is fine, you don't have to worry much about other things since you will start feeding the plants only during the second week.

  6. Also, keep in mind to use fewer nutrients. Do not use full-strength nutes initially because it takes a while for the plants to adjust. For example, using quarter-strength nutrients during the second week will give you a clue of the plant’s needs. Then, you can increase the strength slowly, depending on how the plant performs. 

Summary: Germinating Cannabis Seeds for Hydroponics Systems

The hydroponics system is an enticing and rewarding way to grow potent cannabis plants, but the results won’t be satisfactory if the seeds aren’t germinated well enough.

In summary, avoid using the soil method to germinate cannabis seeds. Instead, the methods of water, paper towel, Rockwool, or starter cubes are best for germinating cannabis seeds for hydroponics. 

And remember, never damage the taproot — it would lead to wasted efforts and disappointment. Keep the temperature and moisture levels in check, and invest in a pH pen to check the pH balance of the cubes before and during the germination process. 

Once the taproot is visible, you can move the seedlings carefully to the medium and kickstart your hydroponics cannabis plant. In addition, just germinating the seeds isn’t enough — you need to care for the seedlings as well. The plant’s yields will depend on how you initially take care of the plant. 

If you grow photoperiod plants, you may have some time to correct your mistakes; however, those growing autoflowers need to be extra cautious since plants that are damaged in the early phases will not perform well later. 



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Hi there 😃 yes, it all starts there, I learned some great stuff about rockwool