If you are anything like myself, you will frequently oscillate between growing with an organic custom blend super soil recipe or taking the leap of faith into the more complex world of hydroponics. For those who have wrestled with their conscience long enough and have decided to opt for the hydroponic route, then firstly, congratulations on challenging yourself, and secondly, let’s learn all you need to know about germinating cannabis systems for hydroponic growing.
We will cover the different soilless growing mediums that can be used, various methods of germinating your cannabis seeds, what can go wrong, and explain how simple and easy starting your hydroponic journey truly is.
TL/DR
Growing cannabis with hydroponics can produce large-sized yields in a shorter time frame.
The optimal temperature for cannabis seeds to germinate is 75.2 degrees Fahrenheit (24 °C).
A cup of water or moist tissue paper between saucer plates will encourage the tap root to grow.
You can use water, paper towel, rockwool, coco coir, peat pellets, oasis cubes, or grow plugs
Cannabis seeds can be planted directly into jiffy cubes 1-2 cm deep and left to germinate.
It is necessary to soak and buffer coco coir and rockwool substrates before planting seeds.
Understanding the Basics: Sprouting Cannabis Seeds for Hydroponics
You may wonder: What is the difference between germinating my seeds in soil, coco coir, rockwool, or oasis cubes? The short and simple answer is that using a soilless medium contains no nutrients and is perfect for transplanting into a sterile hydroponic system. Hydroponic growers will simply plant their seeds into 4-6 inch rockwool cubes or a large pot of coco coir. Cannabis seeds contain enough nutrients for them to germinate and grow, so there is no need for nutrients during the sprouting stage (3-7 days)
What Hydroponic Grow Medium Can I Use for Germination?
There are several ways to germinate your cannabis seeds. Ranging from methods that encourage the tap root to emerge followed by transplanting into the growing medium to the easiest version of planting directly into the growing medium/jiffy.
Water
This method of germination involves using a cup of water to submerge the cannabis seeds. Put the cup in a dark place, such as inside a cupboard. The seeds will drop to the bottom and, within 24–72 hours, will produce a tap root.
Using a glass of water for sprouting marijuana seeds
Paper Towel
Another old-school method involves using wet paper towels and two saucers and placing them in a dark cupboard. When germinating seeds this way, keep an eye on them to avoid letting the roots become too long and entangled with one another.
Sprouting weed seeds with a paper towel method.
Rockwool
Rockwool cubes are those small yellow cubes you see in the trays at the grow shops and are made from basalt (volcanic rock). They contain no nutrients and can hold up to 18 times their weight in water.
Sprout cannabis seeds by using rockwool cubes.
Coco Coir
Coco is my favorite growing medium, and how I always start my seeds off, regardless of later transplanting into soil or hydroponic systems. You can either use a coco coir jiffy plug or plant the young seedlings directly into your large container of coco coir.
Sprout marijuana seeds by Coco Coir peat pellets, quite similar to standard peat pellets.
Peat Pellets
Peat pellets, or plugs, have a very similar appearance to coco coir jiffies; however, peat does contain organic matter, so it is not an inert hydroponic growing medium compared to rockwool or coco coir. However, it is still a great way to germinate seeds before transplanting.
Peat pellets are compacted, nutrient-rich cylinders of peat, used as a planting medium that expands with water, ideal for seed starting and cuttings.
Oasis Cubes
The first time I ever saw an oasis cube over 15 years ago, I was amazed at how great they are. They are basically foam plugs that you insert your seeds or clones inside, water, and allow Mother Nature to do the rest. Oasis cubes may be expensive, but they work like a treat, especially for cloning, thanks to the spongy, airy foam texture.
Sprout cannabis seeds by using Oasis cubes.
What Can Go Wrong When Germinating for Hydroponics?
As a beginner grower, you assume that germinating seeds is straightforward and a matter of planting them into your growing medium and waiting for the Canna Gods to do their magic. This is often the case; however, there are several instances during the pinnacle 7-14 day seedling stage where things may turn pear-shaped.
Temperature Too High Or Too Low During Cannabis Seed Germination
How hot or cold your grow room is depends on the time of year, if you live in a hot or cold climate, the number of grow lights, and the efficiency of your ventilation system. Cannabis seeds prefer an environment that is warm and wet and as close to 75.2 degrees Fahrenheit (24 °C) as possible.
Please make sure to read all about the right temperature in I Love Growing Marijuana’s Grow Bible below.
How To Solve Temperature Issues During Germination:
If your grow room is too hot, raise the height of your grow light or use a low-heat and low-power alternative such as L.E.D. strip lights or T5 C.F.L. strip lights (6400°K spectrum).
On the flip side, if your cannabis plants are experiencing chilling cold temperatures, try using an aquarium heat mat to sit the propagator on, ensuring consistent heat and humidity.
Utilizing heat mats to foster the growth of marijuana plants.
Tall and Lanky Cannabis Seedlings
One of the most common mistakes I notice when speaking with first-time or beginner-level growers is how their seedlings can grow tall, lanky, and with a weak structure. It is not long before the seedlings begin to topple over until they can be supported back upwards.
The main culprit for tall and stretched seedlings is having a grow light too high above the propagator. The other reason is heat stress, meaning the grow room environment is way too hot for the seedlings.
Multiple factors can lead to the stretching of stems in cannabis.
How To Solve Tall and Lanky Seedlings Due To Heat Stress:
The easiest way to solve this annoying problem is to adjust the grow light so the seedlings do not feel the urge to grow as tall as possible. If using an L.E.D. or C.F.L., keep the grow light’s distance between 20 and 40 cm.
Another simple and effective way to deal with scraggly-looking plant growth is to insert a thin cane with a wire tie. I personally love using wooden skewer sticks designed for BBQ skewers!
Pathogens You Might Encounter During The Germination Of Cannabis Seeds
The only pathogen you must worry about during germination is root rot (Pythium). Low oxygen and an oversaturated growing medium are the number one cause of pathogens that affect the roots. Root rot is especially prevalent when starting your seedlings inside a propagator.
The presence of root rot in soil can result in catastrophic effects.
How to solve Pathogen Issues During Cannabis Seed Germination:
Always use clean water when germinating your seeds in a cup or using paper towels and saucers. Thoroughly drain your jiffy cubes until you can gently shake out all the water before inserting your seeds. Check daily that the propagator is not full of water droplets and that the growing medium has no foul-smelling odors developing. 3% food-grade hydrogen peroxide will sort out any early signs of Pythium.
Insects Damaging Your Cannabis Seedlings
Noticing a small part of your leaf missing or signs of some type of insect eating your seeds sprout can be a panic-inducing moment. The thought of a tiny creature ruining your plans for a perfect crop can drive you wild and sometimes take the wind out of your sails during the earliest stages.
How To Solve Insects Damaging Your Cannabis Seedlings:
Do not fear; the Canna Gods have blessed the indoor grower with beneficial predators! You can order various insect predators online or in some grow shops. When it comes to nature, it is best to let these predators fight off the unwanted pests and ensure a healthy population of predators in the garden. If you want to make sure that your plants have the best environment without any pests or diseases, we recommend to use Bergman’s plant protector.
Bergman’s Plant Protector
Protect your plants from diseases and harmful pests.
Consists of three 20 ml bottles
Enough plant protection system supplies for up to 20 plants
Suitable for soil, hydroponic and all other grow mediums
My Personal take/experience
I believe that everyone has their favorite germination methods for optimal growth. As a breeder, I have come across seeds of all shapes, patterns, and sizes and experienced germination times from 9 hours up to one week. The best advice I can personally give is to have a go at germinating using all the growing mediums listed in this article and see which works best and is most practical for your needs and requirements.
Other honorable mentions are not to let the seeds germinate in tissue paper for more than three days, as this will cause the roots to become difficult to transplant later on, and to use tweezers when transplanting into your desired growing medium or doing anything seed-related. Other than checking out Robert Bergman’s Grow Bible and my other article on germinating cannabis seeds in rockwool, peat, and coco coir… good luck learning the ropes and finding the path of least resistance.
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