Learn how to germinate cannabis seeds in rockwool. We go over foolproof step-by-step directions on how to give your seeds the best start possible. In this post we focus on explain the functioning of a hydroponic crop with rock-wool, pointing out the different steps to follow to get a successful c Here’s how to germinate marijuana seeds the easy way with the most success and less hassle.
How to Germinate Cannabis Seeds in Rockwool
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.
Growing cannabis in Rockwool
Rockwool is a product that was first conceived during the 20th century in Hawaii by observing natural volcanic action there. Upon this discovery, a Danish company named Rockwool began to investigate and develop ways to commercialise this technique, and in the late 1930’s released the first standardised stone wool product as we know it today.
To manufacture Rockwool, the raw material of basalt rock must go through several industrial processes, the first of which is melting of the rock in furnaces at extreme temperatures, up to 1600ºC, emulating the action of a volcano and leaving the rock in a natural state of liquid lava.
To obtain the fibres, an organic binder is added to the lava and the mixture is subjected to a mechanical process using centrifugal force, resulting in something resembling a woollen mattress. This wool is then compressed to varying degrees, the density and amount of air between the fibres depending on the projected end use, whether for acoustic or thermal insulation, fire-protection and, of course for it’s use in agriculture.
2. How to stabilise Rockwool
Rockwool Cubes and Slabs
Rockwool substrate is a product that needs to be treated before it’s use. Given that its initial pH level is quite alkaline, nearly 7 points, we should stabilize it to enable us to grow without mishaps from the very beginning.
We must immerse the slabs for 24 hours in a nutrient solution that contains a pH level of 4.5 with EC levels of 0.5-0.6 – ideal to start growing with seeds without worrying about nutrient deficiencies.
When we start to grow the pH level of the slabs should be at 5.5, if that isn’t the case, we should immerse them again during a few more hours checking the pH regularly until it is stabilised. An easy way to know if the pH of the slab is stabilised is to irrigate with water of 5.5 pH and measure the run-off with a pH meter. If the run-off is at 5.5 we can proceed to plant the seeds.
3. How to germinate cannabis seeds in Rockwool
Germination in rockwool
Once the Rockwool cubes have a stable pH as described above, we can proceed with the germination of the seeds we intend to use in our grow.
We will start the germination in two wet paper towels, placed between two dishes in order to maintain a constant humidity and facilitate the germination of the cannabis seeds. Once we see that the seed casing has cracked open and the root appears, we can very carefully transplant them into the stabilised Rockwool cubes and, once established, we can perform the transplant to the slabs.
To transplant the seedlings, we insert the small 3 x 3cm cubes into the 7.5 x 7.5cm Rockwool blocks taped to the slabs. As we do this, we must push gently and slowly until the small cube is well inserted into the larger block, taking great care not to break or damage any roots in the process.
4. How to root cuttings in Rockwool
The process of rooting cuttings in Rockwool is very similar to other cloning methods using jiffies or coco-coir (see how to take cuttings).
After the process of preparing the cuttings for cloning them, we place them in the Rockwool cubes (previously stabilised to pH 5.5) which should be moistened but not soaking wet, to avoid any problems with stems rotting.
Once the cuttings are placed in the cubes we can treat them exactly as if they were in jiffies or coco, monitoring the humidity every day and spraying the cubes to keep a constant moisture on them to ease the rooting. As time goes by it will be necessary to lower the relative humidity until we can finally remove the cover of the mini-greenhouse and start to acclimatise the cuttings so that they don’t suffer when transplanted.
Cuttings in Rockwool cubes
5. How to grow in Rockwool
As previously outlined, the growing medium must be stabilized at pH 5.5 with an initial EC of 0.5-0.6 during this first week of growth, not exceeding two waterings of 1 minute each, with a solution of around 60-70 ml per plant. In this way we will avoid water-logging and facilitate the root growth of plants in this highly absorbent and water-retentive substrate.
To ease the task of watering, using an automatic irrigation system will help enormously and is simple to assemble and use, as you can read in our post on how to install a hydroponic system.
We can maintain this irrigation schedule, varying according to conditions and demand, until the first week of flowering when we will start to gradually increase pH from the initial level of 5.5 , raising it slowly over the course of the week to a level of 5.8-5.9 suitable for this stage of flowering.
Hydroponic crop in Rockwool
From the second until the end of the third week of flowering, we will need to increase the frequency and duration of the irrigations, watering three times a day. The first watering should be of 2 minutes duration when the lights turn on, ensuring the plants start the day with energy. The second watering should be six hours later and 1 minute in duration, with an EC of 0.8-0.9 and a pH of 6.0.
Over the 4th week and until the end of the 5th week of flowering we will again have to increase the frequency of irrigation to 4 waterings at day. The first and the last irrigation should each last 2 minutes, and the remaining two waterings should be 1 minute, distributed evenly through the day. EC levels should remain at 1.0 to 1.2, always taking into account the condition of the plants. We should keep the pH at 6.0 allowing it to fluctuate up to 6.2 to lower it again to 6.0 with pH down.
During the 6th week of flowering it will once again be necessary to increase the frequency of waterings from 4 to 6 per day. The first and last irrigation should last 2 minutes each and the four remaining waterings will each be 1 minute. The EC should still be at 1.4 and the pH continues fluctuating between 6.0 to 6.2 as in the previous week.
In the 7th week of flowering period we will have to keep the same frequency and duration of irrigations; however, in this week, depending on the condition of the plants, we can increase the EC from 1.4 up to 1.6-1.7 and we can also let the pH fluctuate from 6.0 up to 6.3.
In the 8th week of flowering, plants will receive the same number of irrigations, at the same duration as in the previous week, although we can raise the EC to 1.8 depending on the condition of the plants.
In the 9th and last week of flowering phase we will have to increase the duration of all the waterings to 2 minutes, with the pH adjusted to 6.2 and with EC levels as low as possible. We can take advantage of this last week to apply a flush product to help us wash the roots, leaving the plants’ metabolism free of any remaining salts and nutrients and ensuring a far better, cleaner aroma and flavour in the end product.
Hydroponic cannabis grow using Rockwool
6. Recycling Rockwool
Rockwool can be a complicated product to dispose of, given that it isn’t biodegradable. However, today the technology is available to recycle surplus and used material and help to avoid the potential contamination caused by sending it to landfill sites.
The articles published by Alchimiaweb, S.L. are reserved for adult clients only. We would like to remind our customers that cannabis seeds are not listed in the European Community catalogue. They are products intended for genetic conservation and collecting, in no case for cultivation. In some countries it is strictly forbidden to germinate cannabis seeds, other than those authorised by the European Union. We recommend our customers not to infringe the law in any way, we are not responsible for their use.
How to Germinate Marijuana Seeds the Easy Way
There are many opinions about how to germinate marijuana seeds.
Some people advocate putting cannabis seeds in between two wet paper towels.
Others say put them in a glass of water.
Such methods force you to handle your seeds when they’ve just sprouted.
The seeds have to be carefully plucked from the paper towels or water, and just as carefully placed into a growing media.
The extra handling creates opportunities for germinated seeds to be damaged.
The simplest methods that work well are always the best methods.
That’s why I germinate marijuana seeds in the media they’ll grow in.
If the final destination for my seedlings is soil, soilless mix, or coco coir, I put the appropriate material in a JiffyPot and water them from the bottom with reverse osmosis water at 6.1 pH.
You may notice it’s impossible to get accurate pH readings on zero parts per million reverse osmosis water.
I add beneficial microbes such as Voodoo Juice, Piranha, and Tarantula until I get enough parts per million to make my pH readings accurate.
The added benefit of using beneficial microbes products is they protect cannabis roots and root zones, and speed up root development.
If the final destination for my marijuana seedlings is a pure hydroponics system such as deep water culture or an ebb and flow hydro system using rockwool, I plant my seeds into a rockwool cube.
Not the smallest size ones either. I like the larger sizes.
Look here for detailed information that helps you germinate marijuana seeds using rockwool cubes.
Note that rockwool must be pre-treated before use to get its pH where you want it.
Look here for instructions on how to condition rockwool.
The best depth for planting marijuana seed is 3/8 th to ½ inch below the surface line.
The best temperature range to germinate marijuana seeds is 74-76°F, but they can germinate up to 80°F. Warmer than that is too warm.
If you don’t have precision temperature control where your seeds are germinating and temps are too cool, you could use a seedling heat mat.
Be careful to control the seed zone temperature when using a seedling heat mat.
It’s best to get a seedling heat mat with built-in thermostat.
Don’t Drown Your Cannabis Seeds
The biggest mistake growers make when they germinate marijuana seeds is overwatering.
The rockwool cube, soil, soilless mix, or coco that you germinate marijuana seeds in shouldn’t be soaking wet.
The media should be totally damp, but not soaking wet.
If the media is too wet, seeds might rot or drown.
If you have healthy seeds, they should germinate in 2-5 days.
Old or inferior seeds can take as long as 10-11 days.
If they’ve been moist that long and haven’t germinated, they’re most likely not going to.
If your seeds are old or otherwise not fresh or reliable, look at this kit that can help them germinate.
As soon as your seeds germinate, put them under a Hortilux PowerVeg lighting fixture, or some other T-5 or low-power LED, for at least 2-3 weeks until you’re sure your seedlings’ root systems and leaf structures can handle full HID, LED, or sunlight.
Rather than using the paper towel or submerse in water methods, this method we’ve given you to germinate marijuana seeds is direct, easy, and doesn’t require you to handle, transplant, and possibly damage a sprouted marijuana seed.
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