Cannabis Seed Germination Temp And Humidity

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Climate is key to cannabis growing. In this post we analyse the importance of relative air humidity at every growing stage. We’ll define the ideal hygrometric level … Cannabis seeds need only water, heat, and air to break dormancy and germinate; they do not need extra hormones, fertilizers, or additives. Seeds sprout If you read our recommendations on how to choose the best moment to start your outdoor crop, you have probably waited for the good weather to settle in and for the be…

What is the optimum humidity level for each stage of cannabis growing?

In order to start growing in the best possible conditions, it is adamant to understand the meaning of this technical term. Relative air humidity levels give us information on the concentration of water vapour in the air.

It is important to realise that air humidity is closely connected to air temperature, as hot air is more humid than cold air.

That’s why an air conditioning unit dehumidifies and cools the air at the same time.

When air humidity levels come close to 100%, the air is not capable of retaining the excess moisture, which leads to condensation in the shape of small droplets of fog, morning dew, or rain.

For instance, if the temperature of your grow space is 30ºC, with a relative humidity of around 33-35%, and the temperature suddenly plummets to 10-12ºC, the humidity level can quickly reach 100%.

This can become a critical situation at the end of the flowering period if the ‘dew point‘ is reached. This is a parameter that reflects the cannabis flowers’ humidity level. Bad management of the relative humidity levels of your grow space, caused by abrupt temperature variations, could lead to the appearance of mould in your buds.

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So what is the most favourable humidity level for each growing stage?

Here we show you the ideal humidity levels for every growing phase of your cannabis grow.

Germination / beginning of the cuttings’ rooting period

It is really important to maintain a relative humidity of 80-90% in your mini greenhouse during this phase. This applies to seeds that have just sprouted and also to young seedlings (0-10 days old). These still don’t have a strong radicular system and are therefore pretty fragile.

They require high moisture levels so they can concentrate all their resources on the development of a strong and vigorous root mass. The correct day temperature should be 25-26ºC, and 21-22ºC at night.

Young seedlings and 10-day-old clones

At this point, the required hygrometric conditions should range between 70 and 80%, with similar temperatures to those in the initial stage.

The moisture level for this phase needs to be quite high as the root mass is not very vigorous and actually non-existant in the case of the young seedlings. That’s why it’s necessary to point all technical parameters towards this objective.

It is essential to maintain the correct relative humidity as cuttings will start to develop their first roots between 12 and 20 days after having been planted in the growing medium. This is a crucial point for the appropriate evolution of these young plants.

Growing phase

At this stage the young seedlings, derived from seeds or cuttings, will have developed a radicular mass that is significant enough for them to feed through and therefore reach their maximum potential before being transplanted to a new pot for further development.

Establishing new climate conditions at this stage is vital as the aim is to achieve a reasonably high humidity level, but slightly lower than at the beginning. A good balance should range between 60 and 70%.

Temperatures must be kept between 22-28ºC during the day and 18-22ºC at night. These conditions guarantee the plants’ well-being and facilitate good metabolic function, as well as overall optimum development.

At this point, the radicular system is strong enough for the plant to absorb a higher amount of nutrients and develop a much more resistant immune system.

Early flowering

At the start of the flowering period, when the ‘stretching’ or the final growth boost occurs, plants need specific climate conditions for this transitional phase.

As this is still a transition period in which plants progressively end the veg phase, the humidity level needs to be set at 50-60%. It is also essential that the temperature remains between 20-26ºC both day and night.

This prevents thermal shock and guarantees that plants will be ready to produce those delicious flowers. It is vital that their well-being is taken care of so they can concentrate all their resources on their final objective: quality and quantity. These measures are valid for the first 3 to 4 weeks of flowering, depending on the strain.

See also  Gmo Weed Seeds

Late flowering

In the second part of the flowering phase the humidity level must be reduced to 40-50%. In the two to three final weeks it’s preferable for this figure to be closer to 40%.

This is absolutely essential, particularly if you’re growing strains that are sensitive to mould or that produce dense flowers.

If you follow our guidelines, chances of botrytis hitting your flowers will be slim. As far as temperature goes, we advise you to stick to 18-24ºC during the day and 17-20ºC at night.

This way you’ll be able to control your flowers’ dew point, which is crucial in order to prevent fungi and avoid ruining all your hard work.

Author

Brian Worms After completing my studies in International Trade and Marketing in France, I’m more interested in the world of communication today. Blogger, grower and real cannabis toker for more than 20 years, always looking into the rarest and finest cannabis genetics. My passion for cannabis is so deep that it’s become something of a lifestyle now… My work is like a dream come true.

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Jorge’s Cannabis Encyclopedia: Seed Germination

Cannabis seeds need only water, heat, and air to break dormancy and germinate; they do not need extra hormones, fertilizers, or additives. Seeds sprout without light in a range of temperatures. Strong, viable, properly nurtured seeds germinate in 2 to 7 days. At germination, the outside protective shell of the seed splits, and a tiny, white sprout (radicle) pops out. This sprout is the root, or taproot. Cotyledon, or seed, leaves emerge on a stem from within the shell as they push upward in search of light.

Break dormancy: Put newly harvested seeds in the refrigerator for a week or two to simulate winter. Remove and germinate. Seeds will germinate more uniformly because they all come out of dormancy at the same time.

Timeline for Germinating Most Seeds:

At 36 to 96 hours – Water is absorbed, root tip (radicle) pops through outer shell and is visible.
At 10 to 14 days – First roots and root hairs become visible.
At 21 to 30 days – At least half of seeds are rooted by day 21. Seeds not rooted by day 30 will probably grow slowly.

Once seeds are rooted, cell growth accelerates; stem, foliage, and roots develop quickly. Seedlings develop into full vegetative growth within 4 to 6 weeks of germination.

Seeds are Prompted to Germinate By:

water
temperature
air (oxygen)

Water: Soaking seeds in water allows moisture to penetrate the protective seed shell within minutes. Once inside, moisture continues to wick in to activate the dominant hormones. In a few days, hormones activate and send enough signals to pro- duce an initial root tip. The white radicle (rootlet) emerges to bring a new plant into the world. Once a seed is moist, it must receive a constant flow of moisture to transport nutrients, hormones, and water so that it can carry on life processes. Some seeds need lots of moisture to wash out the dormancy hormones in the seed coat, and if they do not get enough moisture, they do not germinate. Conversely, too much water deprives the seed of oxygen, reducing its quality or destroying it. If fragile germinated seeds are allowed to suffer moisture stress now, seedling growth will be stunted. Soaking most seeds in water for 12 to 24 hours is all they need to initiate germination. All the nourishment for a seed’s initial growth requirement is pulled from the fleshy cotyledons, or seed leaves. Water seedlings with low-EC (electrical conductivity) household tap water during the first week or two of life. Supple- mental nutrients are unnecessary and if applied in excess can disrupt internal seed chemistry. Some gardeners prefer to germinate seeds using distilled or purified water that contains virtually no dissolved solids.

Temperature: Overall, cannabis seeds germinate in temperatures from 70°F–90°F (21°C–32°C) and grow best at 78°F (26°C). Temperatures below 70°F (21°C) and above 90°F (32°C) impair germination. Low temperatures delay germination. High temperatures upset seed chemistry causing poor germination. Seeds germinate best under the native conditions and temperature ranges where they were grown.

Air & Oxygen: Sow seeds twice as deep as the width of the seed. For example, 0.125-inch (3 mm) seeds should be planted 0.25 inches (6 mm) deep. Adequate oxygen is un- available for seeds planted too deeply, and tender seedlings have insufficient stored energy to drive through deep layers of soil or crusty hard soil when sprouting.

See also  Germinating Cannabis Seeds In Rockwool

Agricultural Astrology — Planting by the Moon

Ancient Babylonians and Egyptians planted and harvested based on moon phases in relation to geographic location. The premise is that plants grow better when planted during the appropriate moon phase.

Moon phases cause ocean tides to rise and fall. They also affect the rise and fall of moisture in soil and fluids inside plants. The moon phase influence is said to be the same indoors, outdoors, and in greenhouse-grown cannabis.

Cannabis gardeners who plant by the moon report faster-sprouting seeds that grow into vigorous plants. However, scientific evidence is lacking in regard to cannabis and other plants’ relationship with agricultural astrology.

Seeds need oxygen from the air to germinate. Growing mediums that are too moist (soggy) will cut off oxygen supplies and the seeds will literally drown. Cannabis seeds germinate best when moisture is between 60 and 70 percent.

How to germinate weed seeds?

You can germinate your cannabis seeds both indoors and outdoors, though our recommendation is that you do it indoors, as you will have more control over all the factors that can have a negative effect on the process. But if this is not, below we explain the best way to germinate seeds outdoors.

Our first recommendation, as we already said, would be to wait for the good weather to settle in. Having a high temperature (from 22 to 26°C) is an important factor for your seeds to decide to emerge into the world.

Step 1: protect your seedlings from climate factors and fauna, prevention is better than cure.

Outdoors we never know what dear mother nature has in store for us; in the same way that your seeds might enjoy a week of good weather and sun, there can also be thunderstorms and low temperatures on the very day they sprout. Not to mention the large variety of birds, snails and other fauna that delight in eating those tender and tasty marijuana seedlings. Bear in mind that during their first moments of life, your plants are defenceless against many dangers that threaten them; therefore, it is your job to take care of your little ones and keep them safe. How? It’s actually quite simple, you can buy mini-greenhouses for germinating or you can use a Tupperware and make holes in it for adequate ventilation, although we recommend the first option.

Ventilation is an important factor; don’t make the greenhouse airtight, open the trapdoors to allow adequate ventilation and as the covers are made of thin plastic, you can even make some extra holes if necessary.

Step 2: choose quality materials.

Today you can find high quality products on the market, specifically designed for germination and which, in addition, are not expensive. What do you need?

  • Germination greenhouse
  • Electric blanket: If you live in a very cold area, a good solution to stimulate germination is to place an electric blanket underneath the greenhouse, thus achieving an adequate temperature. It is important that the probe that measures the temperature calculates the temperature of the blanket, and not of the greenhouse, as otherwise you might heat the seeds excessively.
  • Jiffy 7: This product consists of of a compressed and dehydrated substrate pellet which, after leaving it in water for a few minutes, becomes a small sack of special substrate for germinating, and is also biodegradable. This is the star product that will optimise your germination process due to the following reasons:

– On the one hand it has the ideal structure, that is, the amount of air and water in the substrate is adequate for germination.

– It is sterilised, meaning that we prevent the appearance of fungi (powdery mildew, botrytis, etc)

– It has all the elements necessary to nourish your seed/seedling during the first week; the ideal amount of nitrogen, phosphorus, potassium, calcium and magnesium. Phosphorus and calcium are particularly important for the correct development of roots.

– It has a neutral pH, which is the most adequate and makes it the perfect medium for germination; during one week you just have to add water.

– Jiffy 7 is expressly designed for the mega-industrial production of seedlings and does not require fertilisation.

– Another advantage is the specific temperature: water has a low specific temperature. This means that if we place a glassful of water in a room at 25°, it will be very hard for the water to reach that temperature. Therefore, if we place the cannabis seeds in a very watery medium (a glass or between paper towels) the temperature will be lower, while in a Jiffy, as it is more exposed to the air, the temperature will be higher and the process, faster.

See also  Autoflowering Marijuana Seeds

However, there are people who germinate marijuana seeds in paper towels. Why don’t we recommend them? Well, although this method may be effective, it is not the most adequate and has some disadvantages. To start with, the seedlings do not receive the necessary light, as the paper towel that covers the top prevents the sun’s rays from penetrating. In turn, in the Jiffy they do receive light, and therefore photosynthesis will start earlier. Another advantage is that as soon as the root emerges in the Jiffy, it starts to turn downwards and to absorb nutrients: on the one hand we accelerate the process and on the other, when we replant the Jiffy 7 with the seedling there is no transplant shock.

Step 3: follow the method.

  • Put the Jiffys in lukewarmwater.
  • Once the Jiffys have expanded, make sure that they are thoroughly wet (don’t squeeze them, just remove the excess liquid if they are dripping). Monitor the pH (between 6 and 7) and the EC (less than 0.5 ms) of the water.
  • Insert the seed in the central hole of the Jiffy, not too deep (approximately 5 mm) with the tip pointing upwards. The marijuana plant must not be sown too deep because otherwise the root has to travel too far: it always emerges through the pointy part of the seed, turns 180°, penetrates into the soil, and once it is secure, it raises its “head” from where the cotyledons will grow.
  • Place the Jiffys in the greenhouse as well as a thermo-hygrometer to monitor the temperature and humidity.
  • Temperature control: it must not fall below 20 degrees nor exceed 30. If you put the greenhouse in the sun, it can get very hot; you must constantly monitor the temperature. If it exceeds 25 degrees, we recommend that you lift up the top cover to ventilate it. Another important factor you have to check is humidity. If it is very sunny, the Jiffys will dry up and it is important that they are always humid. You must therefore add water when necessary, though not in excess. They should only be soaking wet during the first two days. After one week we should already have marijuana seedlings; with their two cotyledons (the first two round -shaped leaves), before the first two real leaves sprout (the serrated leaves), transplant them. If they are autoflowering seeds, we recommend that you transplant them to the definitive flower pot, though if they are feminised seeds you can transplant them to a smaller pot and then, when the plants are larger, you can move them to the definitive pot.

For indoors: The same but under a grow light, fluorescent or LED. If you have the option of germinating your cannabis seeds inside your home, ideally the light intensity will be high; the less intense the light, the more the seedlings will stretch in search of light and become spindly. If you use a 400 W light ideally it should be 40-45 cm away.

Now that you know how to take your first steps, you’re ready to start this season’s crop. Have a good harvest!

Author

Kushka Barcelona-born journalist and grower with a curious spirit. I used to spend my life travelling, writing and working with cannabis clubs until Professor OG called me. My two passions, the plant and the writing, have followed the same path ever since. I absolutely love tricky subjects, those that oblige me to spend days buried in books, investigating and driving the entire technical team crazy. There’s no way I can write a story without going into the issue in depth. I enjoy challenges, but even more sharing them with you on our blog. You can find on instagram at @_kushka.

Categories

  • Cannabis activism
  • Hot news
  • Cannabis Genetics
  • Cannabis Growing
  • Growing techniques
  • Trimming techniques
  • Biological prevention
  • Organic Growing
  • Fungi
  • Indoor Growing
  • Outdoor Growing
  • Harvest
  • Grow Reports
  • Nutrients and fertilizers
  • Plagues
  • Medical Cannabis
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  • CBD
  • Risk reduction

Most popular posts

Can marijuana lead to addiction?

Differences between cannabis and hemp

Cannabis types and varieties

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