By Steven Voser

As dictated by the ancient Chinese philosophy of Yin and Yang, both light and darkness are equally important for the health and harvest of your cannabis plants. Keep reading to learn why darkness is vital to growing great weed.


How Important Is Darkness for Cannabis?

Cannabis is a photoperiodic plant species that relies on light cycle changes to grow and reproduce. When the days naturally grow shorter at the end of summer, cannabis plants sense that their life cycle is coming to an end and start to flower in order to produce the next generation of offspring (or seeds). Females produce pistillate flowers (the ones beloved by cannabis growers), and male plants release pollen in order to pollinate the females.

But what happens when we take cannabis out of its natural habitat and cultivate it in an outdoor garden, indoor grow room, or a greenhouse? While there are countless ways in which we can manipulate the way cannabis plants grow, we still have to (or should) abide by some of nature's laws to avoid complete chaos. And that's exactly the case when it comes to darkness.

While as growers we have the ability to maximise the growth of our plants using special lighting, nutrients, training techniques, and even extended light cycles, one thing remains certain—cannabis plants need at least some moments of darkness to grow properly and produce the flowers we treasure. Without a healthy light/dark cycle, cannabis plants may not start flowering at all or demonstrate signs of stress, such as stunted growth, poor flower production and structure, or hermaphroditism.

Hermaphrodite Cannabis Plant
Hermaphrodite Cannabis Plant

What Do Cannabis Plants Do During the Dark Period?

Cannabis, like all green plants, photosynthesises when it receives light (be it from the sun or from a grow light). Using light energy as fuel, plants are able to take water and carbon dioxide from their environment and turn them into glucose and oxygen. At the same time, plants also respire, releasing surplus oxygen into the environment while simultaneously breaking down the sugars produced during photosynthesis into usable energy.

In the dark, plants use the energy they produce during the day (or in the presence of light) to turn carbon dioxide from the environment into glucose and other simple sugars that they can use to help further fuel their growth. At the same time, respiration also occurs during the dark cycle—just like us, plants only stop respiring when they're dead or dying!

How Much Darkness Do Cannabis Plants Need?

Cannabis plants need different amounts of darkness during different stages of their life cycle.

Darkness in cannabis plants

Germination / Seedling Phase

Light is not a strict requirement for seed germination. The three main requirements needed to germinate cannabis seeds are water, oxygen, and the right temperature, and most growers opt to germinate their seeds in the dark. However, light becomes very important as soon as a seed sprouts. Without adequate lighting, cannabis seedlings can quickly become leggy, which can leave them fragile and prone to falling over or damping off.

Cannabis seedlings should be exposed to high-quality, cool light for around 18 hours per day. Make sure to place your lights around 2 inches from the tops of your seedlings to promote healthy growth and avoid stretching/legginess (i.e. etiolation).

Vegetative Phase

Photoperiod cannabis plants need at least 14+ hours of light per day in order to stay in the vegetative phase. Now, exactly how many light hours you choose to give your plants is up to you; in fact, growers readily debate this topic all the time. In general, however, most growers opt to give their plants 18 hours of light followed by 6 hours of uninterrupted darkness during the vegetative phase.

That said, some growers opt to veg their plants under 24 hours of continuous light, and achieve good results. Besides a hefty power bill, however, a 24-hour light cycle may produce stress in some plants, which can result in poor growth and subsequently a poor harvest.

Alternatively, some growers choose to keep their plants under 6/2 cycles—that is, 6 hours of light followed by 2 hours of darkness. After three repetitions of this cycle, the plants will have received 18 hours of light and 6 hours of darkness, but some growers argue that the short breaks allow the plants to rest and process CO₂ more effectively.

Moreover, plants that are grown in 6/2 cycles won't flower, as photoperiod cannabis needs to be exposed to 12 hours of continuous darkness in order to enter their bloom phase.

Flowering Phase

In order to flower, photoperiod cannabis plants need to sense that winter is coming—literally. To simulate this in an indoor room or tent, you'll need to dial back your light hours. Again, there's a lot of debate about the perfect ratio of light and darkness for flowering cannabis plants, but most growers opt for a 12/12 light/dark cycle.

Note: Cannabis plants won't flower immediately after you change your light cycle, and many growers suggest gradually decreasing a plant's light hours to ease them into the bloom phase without causing them any stress. Others, however, opt for a more abrupt change, leaving their plants in complete darkness for up to 36 hours before switching to 12/12 lighting in order to ensure an effective transition from veg to bloom.

Why Put Cannabis in the Dark Just Before Harvest?

It's harvest time and your plants are heavy with sweet flowers. Time to cut 'em down, right? Not according to some growers. A large number of cannabis cultivators recommend subjecting harvest-ready plants to 24 hours of darkness (or even 48 hours) before cutting them down. The argument here is that the sudden light deprivation stresses the plants, causing them to produce more resin, and thus more THC and terpenes.

Unfortunately, this theory has not been proven. And while some growers claim to experience success with the methods, we recommend you take those results with a grain of salt, as many variables could have influenced them.

Are All Light Cycles Made Equal?

While some growers like to experiment with different light cycles (as we saw above), most indoor growers follow an 18/6 cycle during veg and a 12/12 cycle during bloom. Similarly, most outdoor growers plant their seeds nice and early in the season to make the most of the long days and maximise their plants' vegetative growth.

But do these standard practices really ensure the best results come harvest time? Research from Australia[1] suggests that maybe not. In an article from 2023, researchers from New South Wales Department of Primary Industries, The University of Melbourne, and Southern Cross University studied the effects of different light cycles on the yield and cannabinoid production of different cannabis varieties.

The researchers tested the effects of different light cycles (12/12, 10/14, and 14/10) on three varieties of cannabis—Cannatonic (a high-CBD strain), Northern Lights, and Hindu Kush (both high-THC strains). They found that plants that began flowering under a 14/10 cycle produced the heaviest yields, and Cannatonic produced between 50–100% more CBD under these conditions. Meanwhile, the two high-THC strains produced notably less THC under the 14/10 cycle, despite producing more flowers.

Many growers are familiar with how sensitive cannabis is to light. This research, however, suggests that light sensitivity may vary among different cannabis varieties, and further research like this could help to identify new approaches to light cycle management beyond the standard 18/6 for veg and 12/12 for bloom, bringing out the best results in different cannabis varieties.

Do Autoflowering Cannabis Plants Need Darkness?

Video id: 527684146

Autoflowering cannabis plants are derived from Cannabis ruderalis, a unique cannabis variety that flowers based on age rather than in response to light cycle changes. Since autos are not photoperiodic, many growers have been led to believe that these varieties can (or even should) be grown under 24 hours of light from seed to harvest in order to maximise plant growth and yields. However, we advise against this.

As we saw at the beginning of this article, many key plant processes occur during the dark phase. Moreover, nowhere on Earth except the Arctic (where cannabis doesn't grow naturally) do we see plants exposed to 24 hours of light per day. And we tend to think that nature knows best, which is why we choose to grow autos under a 18/6 light/dark cycle, and recommend you do the same.

Ways to Ensure Total Darkness for Your Cannabis Plants

To maximise the health of your plants and the size and quality of their yields, it is important that your grow space is free of light pollution. Failure to ensure this can result in stress and even the revegetation of blooming cannabis plants. If you're growing indoors, the best way to do this is to invest in a quality light-proof tent. If you're growing outdoors, make sure to keep your garden lighting off during the night. Also, if you live in a densely populated area (such as a city), keep your plants as far away as possible from any other sources of light (streetlights, your neighbors' garden lighting fixtures, etc.).

Embrace the Darkness to Boost Your Yields

As cannabis growers, we're often tempted to "play God" and manipulate our plants to achieve bigger harvests. At RQS, however, we prefer to grow cannabis the way nature intended, which is why we recommend giving your plants a good dose of darkness just like they'd enjoy when growing out in nature. Do this, and you'll be sure to grow healthy plants and harvest spectacular buds.

External Resources:
  1. Plants | Free Full-Text | Moving Away from 12:12; the Effect of Different Photoperiods on Biomass Yield and Cannabinoids in Medicinal Cannabis https://www.mdpi.com
Disclaimer:
This content is for educational purposes only. The information provided is derived from research gathered from external sources.

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Privacy Policy - Royal Queen Seeds

To ensure a safe online environment and guarantee adequate data protection, we strictly comply with all legal requirements. In this privacy statement, we provide information about how and for what purpose data is collected, safety measures, storage periods and contact details.


COMPANY NAME: SNORKEL SPAIN, SL (hereinafter ROYAL QUEEN SEEDS)

C/ Vilar d'Abdelà, 5 (nave 1) CP: 08170 de Montornès del Vallès

+34 937 379 846

support@royalqueenseeds.com


The present Privacy Policy sets out the terms on which we will treat personal data at ROYAL QUEEN SEEDS; this includes any personal data collected through our website https://www.royalqueenseeds.com/ as well as any other data we process in the course of our business activities.

ROYAL QUEEN SEEDS collects the following personal data for the purposes listed below:

SECTION 1 – PERSONAL INFORMATION WE COLLECT

1.1 Account purchases

Account purchases can only be made if you are in possession of a personal account. When you create an account or purchase something from our shop, as part of the buying and selling process we collect the following personal information that you provide to us:

This information is required for delivery. In addition, when you browse our shop, we automatically receive the Internet Protocol (IP) address of your computer. Based on this information, we can optimise your online experience and at the same time protect our online environment.

Purpose of data collection

We collect and store account-related data for the following purposes:

(a) to carry out obligations arising from any contracts between you and us, and to provide you with information, products and services that you may request from us;

(b) to set up, manage and communicate with you about your account and your orders;

(c) to conduct market research and analysis;

(d) to confirm your age and identity, and to detect and prevent fraud.

1.2 Newsletters

With your explicit permission, we may send you newsletters about our shop, new products and other updates. We send newsletters based on your explicit consent. In the event that you purchase a product, and in accordance with current regulations, we may send you commercial communications in accordance with the legitimate interest of our company, always about products or services similar to those you have purchased or contracted. In any case, you may exercise your right of opposition through the channels announced in this Privacy Policy. The following information is collected in relation to the newsletter:

We do not need to know the sex of the person in order to send the newsletter (data minimisation: by law we must ask for data that is strictly necessary to provide the service, and in this case knowing the sex is not necessary to send the newsletter).

Purpose of data collection

The data collected is used to:

(a) personalise our emails, including your name and gender;

(b) provide gender-specific content.

You can withdraw your consent at any time by using the link provided in the newsletter or the contact information provided in section 2.

1.3 Customer service and contact form

In order to provide appropriate support, our customer service employees have access to information related to the account. Consequently, their support will be highly effective and friendly. The data provided in our contact form is used by our CRM provider, SuperOffice. We will only use your details to respond to your message.

SECTION 2 – LEGITIMATE INTEREST

If you have purchased any of our products, please note that we may process your personal data for promotional purposes, based on Royal Queen Seeds' legitimate interest only to offer you products or services from our company and about products or services similar to those you have purchased. You may exercise your right to opt out of future messages by the means set out in this Privacy Policy or through any notification you receive.

2.1 How do you withdraw consent?

If you change your mind, you can withdraw your consent for us to contact you for the purpose of collecting, using, or disclosing your data at any time by reaching out to us at: support@royalqueenseeds.com.

SECTION 3 – DISCLOSURE

We may disclose your personal information if we are required to do so by law or if you breach our Terms of Service.

SECTION 4 – HOW LONG DO WE KEEP YOUR DATA?

At Royal Queen Seeds, we will not retain your data for longer than is necessary for the purposes described in this Policy. Different retention periods apply for different types of data; however, the longest period we will normally hold any personal data is 10 years.

4.1 Account information

Data relating to the account remains relevant for as long as the consumer is in possession of an account. Therefore, the data remains documented for as long as the account exists. When our customers delete an account, the associated data will be deleted within a reasonable period of time. Requests regarding the inspection or correction of stored personal data or the deletion of an account can be sent to support@royalqueenseeds.com.

4.2 Newsletters

In the event that you give us your consent to inform you about our products or services, we will keep your data until you express your wish not to receive any further communications from us. However, we regularly (every month) carry out a relevance check. Registered customers (and their personal information) will be deleted whenever customers do not reply to our request. In addition, our newsletter mailing has an opt-out feature. Consumers can withdraw their consent by using this opt-out feature.

SECTION 5 – COOKIES

Cookies are small information files that notify your computer of previous interactions with our website. These cookies are stored on your hard drive, not on our website. Essentially, when you use our website, your computer displays its cookies to us, informing our site that you have visited before. This allows our website to function more quickly and remember aspects related to your previous visits (such as your username), making your experience more convenient. At Royal Queen Seeds, we use two types of cookies: functional and analytical.

5.1 Functional Cookies

Functional cookies are used to enhance your online experience. Among other things, these cookies track what is added to your shopping cart. The use of these cookies does not require prior authorization.

5.2 Analytical Cookies

Analytical cookies are used for research and market analysis. The data collected with these analytical cookies is anonymous, making it unusable for third parties. The use of these cookies does not require prior authorization.

SECTION 5 – THIRD-PARTY SERVICES

Third-party services are required to conduct transactions and provide our services. In general, the third-party providers we use will only collect, use and disclose your information to the extent necessary to enable them to perform the services they provide to us.

However, certain third-party service providers, such as payment gateways and other payment transaction processors, have their own privacy policies regarding the information we must provide to them for your transactions.

We encourage you to read the privacy policies of these providers so that you can understand how these providers will handle your personal information.

In particular, certain suppliers may be located or have facilities located in a different jurisdiction than yours or ours. Therefore, if you choose to proceed with a transaction involving the services of a third party, your information may be subject to the laws of the jurisdiction in which that service provider or its facilities are located.

Once you leave our website or are redirected to a third-party website or application, you are no longer governed by this Privacy Policy or the Terms of Service of our website.

Web analytics service (anonymous data)

On this website we have integrated an element of a web analytics service (with anonymisation functionality). Web analytics can be defined as the gathering, processing and analysis of data about the behaviour of visitors to websites. An analytics service collects, among other things, data about which website a person came from (the so-called referrer), which sub-pages they visited or how often and for how long they visited a sub-page. Web analytics is mainly used for website optimisation and for a cost–benefit analysis of internet advertising.

Courier service

To complete deliveries we use a courier service. This courier service carries out the delivery between our company and the consumer's home. To complete these logistics, the company requires access to the consumer's name and address information.

Mailing service

Royal Queen Seeds uses a third-party mail service provider to send its newsletter. This provider has access to limited account information related to opt-in consent (e.g. email address).

Marketing services

Royal Queen Seeds has the support of a company that specialises in marketing and communication activities. Their access to personal information is very limited and mostly anonymous.

Payment services

At Royal Queen Seeds we use external payment services to handle our transactions (e.g. credit card payments).

SECTION 6 – SECURITY

To protect your personal information, we take reasonable precautions and follow industry standard best practices to ensure that it is not inappropriately lost, misused, accessed, disclosed, altered or destroyed.

If you provide us with your credit card information, the information is encrypted using secure socket layer technology (SSL) and stored using AES-256 encryption. Although no method of transmission over the internet or electronic storage is 100% secure, we follow all PCI-DSS requirements and implement additional industry standards that are commonly accepted. Information related to the account is protected with a hashing method. This method transforms the information into a generated hash. As a result, confidential information is protected and invisible, even to us. In addition, our databases are exceptionally protected against unauthorised access. For example, access to the database is only possible and permitted via approved IP addresses (e.g. from Royal Queen Seeds headquarters). Other attempts and addresses are rejected at all times.

Furthermore, data is anonymised as much as possible, so it cannot be directly linked to a specific consumer. With this data, however, we may be able to carry out market research and analysis. In addition, the third parties concerned (e.g. mailing service) are examined prior to our collaboration, comply with the GDPR from the EU and receive a processing agreement. Within Royal Queen Seeds, employees are assigned different access permissions. Specific permission provides access only to information that is strictly required to perform a task. Digital security measures are subject to change and must meet high requirements to ensure the safety of online customers. That is why, at Royal Queen Seeds, we appoint a security officer. Regular verification and improvement of security measures (where necessary) are part of the role.

SECTION 7 – CHANGES TO THIS PRIVACY POLICY

We reserve the right to modify this Privacy Policy at any time, so please check back regularly. Changes and clarifications will be effective immediately upon being published on the Website. If we make substantial changes to this policy, we will notify you here that it has been updated so you will know what information we collect, how we use it and under what circumstances, if any, we use and/or disclose it.

SECTION 8 – YOU HAVE THE RIGHT TO: