Hi and welcome to my guide on how to grow cannabis seedlings hydroponically.
The objective of this lesson is to learn the proper lighting, temperature, nutrient, testing
and cleaning procedures to grow cannabis in a hydroponic setup during the seedling stage
of growth.
All links mentioned in this video can be found in the video description, along with a link
to Indica Institute where you can find a growing list of cannabis related courses and recommendations
on the best products for purchase.
Now that your seed is germinated, it’s started the seedling stage.
This is the stage from when your plants grow their first serrate leaf until about 3-4 sets
of leaves.
Take your sprouts from the germination pod and place them in your desired medium - clay
pebbles, rockwool, perlite or coco coir - where it will hopefully spend the next 2-3 weeks
without interruption.
What I mean by this is to leave your seedling roots untouched, including the reservoir of
water, for 2-3 weeks before refreshing.
I will explain this in greater detail in the last part of this video entitled “added
tips”.
Your seed should not see light until there is a sprout that breaks the surface of the
grow medium.
It is at this point that you should implement a light schedule of 18-6, up to a full 24
hours of light a day.
There are arguments for all variances of light scheduling, and there is no real wrong answer
here - so long as your plants get at least 18 hours of light every 24 hours.
Regardless of the lighting setup you are using, keep a close eye on your plants during this
stage.
Your plants can grow very quickly, especially in a hydroponic setup, so ensuring that it
is not too close to your lighting is important to avoid light burn.
HID lighting is usually still too powerful to use on your newly sprouted seedlings, so
it’s best to use CFL or an LED light with a dimmer.
Make sure to keep the light about 18 inches away from the top of your sprouts.
With CFL lights keep your light 6 inches from your plants.
Additionally, remember to apply the hand test when in doubt.
This means floating your hand just over the top of your plant canopy and leaving it there
to see if it starts to heat up or burn as a result of the heat coming from your light.
If that starts to happen, imagine what it’s doing to your plant!
Move your light further from your canopy.
As far as temperature, cannabis plants thrive in an environment between 22 and 27 degrees
Celsius or 73 to 80 degrees Fahrenheit.
Optimal temperatures are between 23 and 25 degrees.
Many hydroponics growers adamantly argue that it is best to grow hydroponically at a lower
temperature, while others are for the camp of warm temperatures.
Here, I can only give you my opinion and my personal experience with my own grows and
the rationale for me doing so
The proponents of a colder climate for plant growth when growing hydroponically will cite
that it makes for an inhospitable environment for the growth of those microorganisms that
cause root rot.
Additionally, water holds oxygen better at lower temperatures which feeds into the plant
at greater levels and promotes growth.
On the other hand, lower temperatures slow plant growth, thus the plant requires less
oxygen to grow at pace.
What's more, cooler temperatures are not a guarantee that your reservoir won’t develop
the microorganisms that cause root rot anyway.
What it will guarantee though, is that it will stunt the growth of your plants.
Additionally, your reservoir will require that your pump be running constantly and your
airstone never stops pushing more bubbles into the water.
This will generate more than enough oxygen for what your plants will need.
Either option you choose, it's strongly advisable you get a beneficial additive like Hydroguard
to protect your roots.
So if you are using a protecting additive, you may as well create the best environment
for plant growth.
As far as your water temperature, try to keep your reservoir at around 20degrees celsius
or 68 degrees fahrenheit.
Invest in a water thermometer to keep track of this, and if necessary purchase a fish
tank heater to keep the temperature manageable.
Starting out the relative humidity should be around 60.
Without much roots yet the sprout will primarily rely on water in the air to survive.
As the sprout grows solid roots though your plants will require more oxygen, so it’s
important to slowly work the relative humidity down from there.
You will want the humidity range to be around 50% by the time flowering hits, and 40% by
harvest.
Keeping humidity down as your plants get bigger has the benefit of pushing your plants to
generate stronger root growth in an effort to absorb water this way, instead of from
the air.
Nutrients should be added to your reservoir on your first fill.
Unlike growing in soil where there are nutrients readily available for consumption by the plant,
water contains far less readily available nutrients for your plants to pull.
While your seedlings will still grow without it, the added nutrients will boost the growth
rate substantially.
Start with either seedling stage nutrients at half the dosage, or vegetative stage nutrients
at one quarter the recommended dosage.
It's always better to have not enough nutrients in your water than too much.
If you notice that your plants are starting to yellow or brown and get crispy, immediately
replace your water with a lower nutrient dense water.
Alternatively, if the plant seems pale and the pH is where it should be, then it could
be that your plant requires a bit more nutrients.
Again, your water should be right around 20 degrees Celsius, or 68 degrees Fahrenheit,
and full of bubbles.
The more bubbles, the more oxygen your plant has to thrive in.
The whole benefit behind growing hydroponically is for it’s quick speed, so in order to
happen it must be supplied with everything it needs to keep up with it’s growth.
This includes plenty of oxygen for a healthy root structure.
Your water should be tested regularly for pH levels and PPM density.
As for the pH of your water, nutrients are more readily available in a slightly acidic
environment.
Optimally your plants will grow in a pH of 5.5 to 5.8, but this will move up to 6 later
as the plant enters the flowering stage.
Change your solutions and reservoir weekly once the seedling stage is done to keep within
this range.
As far as your PPM reading, during the seedling stage you should be looking at a range of
about 100 to 250.
This will jump as you move through each stage of plant growth, so be sure to check my videos
on how to grow cannabis hydroponically at each stage for more information related to
each stage specifically.
Before you get started, let me just remind you of a few basics.
First, remember to wipe everything down with rubbing alcohol, hot water and peroxide before
getting started.
Make sure your whole grow space is sterilized, and ensure that you don’t track the outside
world when you come to visit your girls either.
Have clean sterile clothes and shoes on stand to switch over to when you go into your tent.
Lastly, while you should normally be replacing and cleaning your reservoir weekly, for the
first few weeks while your seedling is getting used to its new environment it should be left
completely alone.
Test your water and top up as necessary, but they are particularly susceptible to being
stunted in their growth this early.
As long as you are using a beneficial additive to fight off the bacteria that causes root
rot, your reservoir should be able to last an extra week or so to let your seedlings
really establish their roots.
So in review, before getting started, be sure to wipe all your grow equipment down with
rubbing alcohol, water and peroxide.
Your seeds should not receive any light until they sprout above the surface of the grow
medium, at which point they should get at least 18 hours of light a day.
A scheduling of 18-6 or 24-0 can be debated, though it is universally agreed that 18 hours
of light is the minimum.
Keep a close eye on plants and the distance between your canopy and the light.
Keep around 18 inches away from your canopy and apply the hand test when in doubt to avoid
light burn.
Temperature should be between 22 and 27 degrees celsius or 73 to 80 degrees fahrenheit, and
be sure to use a beneficial additive in your water to fight the growth of bacteria that
causes root rot, such as hydroguard.
The temperature of your water should be around 20 degrees celsius or 68 degrees fahrenheit.
Humidity starting out should be around 60 RH, though this will drop as your plant develops
a proper root structure and relies more on this for water than pulling it from the air
around them.
Add nutrients to your reservoir from the first fill.
Use a half dose of seedling nutrients or a quarter dose of vegetative stage nutrients.
When in doubt, always start with less and work your way up.
Your water should again be at 20 degrees celsius or 68 degrees fahrenheit, and regularly pumped
with bubbles.
The more bubbles the better.
Regularly test the pH levels and PPM density.
pH should be between 5.5 and 5.8, while PPM should read at about 100-250 during this stage.
I hope you found this installment of my course on “How To Grow Cannabis Hydroponically”
useful.
For more cannabis related courses or recommendations on the best grow products out there, visit
me at indica institute or subscribe to my YouTube channel.
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