Intro from Dutch Passion Cannabis Seed Company

As more people than ever grow premium quality autoflowering cannabis seeds, the debate about the best autoflower cannabis plant light schedule continues. Outdoor growers get great results despite the daily light hours changing from one month to the next. 

Occasionally indoor growers may be obliged to finish a few autos alongside their photoperiod feminized strains under 12/12 light. But most indoor growers use an autoflower cannabis light schedule using from 18-24 hours of daily light. With around two decades of experience developing autoflower seeds, Dutch Passion have some useful advice for those wanting to know the best autoflowering cannabis plant light schedule.

How much light does autoflowering cannabis need?

An autoflower grown for 10 weeks/70 days with 20 hours of daily light will take around 1400 light hours to grow from premium autoflowering cannabis seeds to harvest. Curiously, that’s around the same number of light-hours as a photoperiod feminized strain grown with a 5 week veg period (18/6 cannabis light cycle) and 9 weeks bloom (12/12 light).

Freed from the rules of photoperiod dependency, premium autoflowering cannabis seeds cruise rapidly through their growth cycle, delivering heavy yields and potency on-a-par with the best feminized strains. But premium autoflowering cannabis seeds generally reach harvest a month (or so) faster than most feminized strains.

Despite the obvious attractions of the best autoflower seeds, feminized strains have a massive amount to offer and remain equally popular with most growers.

What is the best light cycle for my autoflower?

Dutch Passion recommend 20 hours of daily light from autoflower seed to harvest. Over many years that seems to offer the best combination of growth. But it’s also fair to say that we have seen sensational results from growers using anything from 18-24 hours of daily light.

Some indoor growers may occasionally find an autoflower has to be inconveniently finished under 12/12 light conditions alongside a photoperiod feminized crop. In such cases the autos should all complete bloom, but yields will unfortunately be inevitably compromised.

Many outdoor growers now routinely plant premium autoflowering cannabis seeds alongside their trusted outdoor photoperiod strains. Depending on your climate you may be able to harvest anywhere from 1 to 3 consecutive autoflower crops per year.

Daylight hours vary from country to country and from season to season. But premium autoflowering cannabis seeds have proven resilience and adaptability to adjust effortlessly to whatever comes in terms of the cannabis light cycle delivered at that particular latitude. 

This demonstrates the adaptability of autoflower strains. It also shows that premium autoflowering cannabis seeds will complete their growth cycle regardless of the light cycle. However indoor growers are advised to use an autoflower light schedule which includes at least 18 hours of daily light and preferably 20 hours, which may offer slight yield improvements over an 18-hour light cycle.

So what is the best light schedule for autoflower cannabis plants?

Experienced growers with well controlled environmental conditions can keep their autos thriving in the optimized nutrient and optical sweet spot all the way from autoflower seed to harvest. Master growers will get great results with premium autoflowering cannabis seeds using anywhere from 18 to 24 hours of daily light. Reducing light hours much below 18 hours of daily light will, however, incur yield reductions. 

Less experienced growers finding out how to grow cannabis and struggling with the varying light requirements of their autoflower plants at different stages of growth should beware of overloading their plants photosynthetic capacity. Especially when using new, powerful LED lights at high PPFD levels with a 24-hour light cycle.

Dutch Passion consider the best indoor autoflower light cycle to be one that uses 20 hours of daily light with a 4 hour ‘rest’ period of darkness. This seems to allow reliably strong growth, good plant development and great biochemistry for cannabinoid and terpene production.

Bonus lighting tips for autoflowering cannabis seeds

Our two main lighting tips on how to grow cannabis to the best potency levels are to use quality LED lights and also UVA/UVB lights. A few years ago, LED was financially out of reach for most growers. Nowadays an LED upgrade is probably the best investment any HPS grower could make. Top auto strains such as Auto Skywalker Haze, Auto Cinderella Jack, Auto Kerosene Krash and Auto Lemon Kix can hit 25% THC and higher in optimized LED lighting.

Total cannabinoid content, THC levels and terpene loading all increase when upgrading from HPS to LED. These significant improvements come thanks to the superior light spectrum of LED and inherently lower heat/IR emissions. What’s more, you may also be able to grow with a little less electricity (and less air-con for those that use it). Currently, electricity represents the main cost for most indoor cannabis growers.

UVA/UVB lights are also highly recommended for those wanting to know how to grow cannabis with the very highest THC/cannabinoid levels and the best terpene profile. Although advances are being made in UVA/UVB LEDs, fluorescent UVA/UVB lights currently offer the best value for money. If you’re a serious grower aiming to squeeze every trichome of genetic potential from your premium autoflowering cannabis seeds, then a supplemental UVA/UVB light could/should be the next grow room gadget on your wish-list.

Other than recommending the use of LED alongside supplemental UVA/UVB lights, Dutch Passion have one slightly more generalized top-tip on how to grow cannabis. That is to master the art/science of hitting the nutrient and optical sweet spot for your plant needs during every stage of growth. As any time-served grower will know, this takes time and patience to master. Making records of key grow-room parameters at each stage of your grows can be a great help as you get to know how to grow cannabis better. 

Connoisseur growers with the experience to know how to grow cannabis with precision-control invest in light meters. These allow the pro-grower to find and record optimized PPFD light levels across their particular grow room at each stage of autoflower plant growth, giving them the tools to precisely increase light levels as plants mature. They will also need to be able to spot the first signs of light stress.

Learning how to grow cannabis professionally comes through researching the best options combined with your ability to apply the best advice/learnings! In addition to creating some of the highest quality cannabis seeds since 1987, the Dutch Passion experts are thrilled to help growers from everywhere in the world to grow their knowledge and skills!