Photoperiod vs. Autoflowering Cannabis: Which Is Right For You?

Luke Sumpter

Cannabis Journalist & Health Science Researcher

Luke Sumpter

Last updated: November 30th, 2022

Cannabis is one heck of a complex plant. The species produces over 100 cannabinoids, over 200 terpenes, and many other interesting chemical constituents. The ratios of these molecules can vary between strains, and even between plants of the same strain. Adding to the complexity is the number of cultivars on the market. There are around 800 known strains, but it's likely that many more exist.

These cultivars stem from landrace genetics obtained from different regions of the planet. Breeders select landraces for hybridisation based on specific desirable traits. Due to evolutionary adaptation, landraces have developed extraordinary genetic differences. One such divide occurs between photoperiod and autoflowering genetics.

These traits alter the flowering time and difficulty of cultivation between strains, along with other factors. Choosing between photoperiod and autoflowering cultivars is one of the first decisions that many growers make well before placing seeds into the soil. In this article, we'll cover the key features of both types of cannabis. Then, we'll delve into the pros and cons of each to discover which is right for you.

PHOTOPERIOD VERSUS AUTOFLOWERING CANNABIS: THE DIVIDE

The primary difference between photoperiod and autoflowering varieties is how they initiate flowering. The vegetative phase is the first major stage of the growing cycle, and occurs after a brief seedling phase. During this time, plants are busy consuming nutrients, expanding their root systems, and producing large fan leaves.

After the vegetative phase, plants begin to produce flowers. These structures house glandular trichomes that produce valuable cannabinoids and terpenes.

Cannabis is an annual plant, meaning it grows from seed, matures, and dies over a single season. Photoperiod and autoflowering plants detect seasonal changes in different ways; this is because they evolved in, and adapted to, different environments.

The very word "photoperiod" refers to the time frame of light exposure. These cultivars shift into flowering mode when their light cycle changes—an entirely natural response. Outdoors, this happens when summer transitions into autumn and the days get shorter. Indoors, growers need to initiate flowering by reducing the amount of light their plants receive. Photoperiod strains take considerably longer to reach harvest, however, they often produce much larger yields and feature higher levels of cannabinoids.

In contrast, autoflowering varieties don't require a change in light cycle to initiate flowering. Instead, they are genetically programmed to flower after a certain amount of time. Autoflowering plants boast rapid growth and ease of maintenance. They grow much smaller than most photoperiod strains, and therefore usually produce a lower yield.

COMPARING AUTOFLOWERING AND PHOTOPERIOD CANNABIS

Both photoperiod and autoflowering cultivars pose a long list of advantages, as well as a couple disadvantages. They differ in many ways, including speed, yield, difficulty, and even appearance. However, both are capable of producing top-quality bud!

Let's dive deeper into the differences between these types of cannabis.

EVERYTHING ABOUT AUTOFLOWERING CANNABIS

Autoflowering varieties are favoured by growers looking to obtain a high-quality harvest as fast as possible. Growers value autoflowers for the short amount of time it takes them to explode from seed to harvest. Their small size also makes them compatible with stealthy indoor grows and outdoor guerrilla grow operations. Check out the list below to discover their traits in full detail. If they appeal to you, take a look at our 10 best autoflowering seeds.

Top 10 Autoflowering Seeds

GROWING

All autoflowering hybrids contain genetics from a cannabis subspecies known as ruderalis. Cannabis ruderalis is native to Eastern Europe and Central Asia, and therefore evolved with a much shorter growing season than her photoperiod sativa and indica counterparts. Ruderalis plants had to germinate, vegetate, and flower before the first frost arrived. In general, autoflowering varieties will go from seed to harvest in around 8–12 weeks. The trait is especially useful for covert growers looking to maintain discretion, and commercial cultivators looking for a quick turnover.

Autoflowering plants don't require as many nutrients, but do need a well-aerated potting mix. Add perlite to the growing medium to ensure proper airflow.

APPEARANCE

Pure Cannabis ruderalis varieties are the smallest subspecies of cannabis. They feature minimal bud sites and low levels of cannabinoids. They produce small leaves featuring three primary fingers and two tiny, backward-facing fingers. Pure ruderalis is only really grown for breeding purposes.

Breeders have hybridised high-performing photoperiod strains with ruderalis genetics to endow them with the autoflowering trait. These hybrids typically grow to 60–100cm in height. However, some cultivars are known to peak at 130cm. They are stocky, and many growers opt to use methods such as low-stress training to alter their shape and promote lateral growth.

YIELD

Speed and ease of growth come with a tradeoff; autoflowering yields are mostly smaller than those obtained from photoperiod varieties. Autoflowering cultivars also received the trait of reduced productivity. But, it's not all bad news. Growers typically achieve a yield of around 400g/m² indoors. Their smaller size also means cultivators can grow many more plants within a particular space.

DIFFICULTY

Autoflowering strains are easy to grow. Like, super easy. A colder and more brutal climate made ruderalis a hardy beast; she's very forgiving when it comes to beginner error. Autoflowers can take a beating—they're quite hard to kill. They are often found growing wild in soil with few nutrients. This trait makes them ideal for beginner growers.

PROS

• Easy to grow
• Fast life cycle
• Greater variety than before
• Covert size
• Resilient

CONS

• Small size equates to lower yields
• Slightly lower potency than most photoperiod strains
• Easier to overfeed
• Can’t use high-stress training techniques

EVERYTHING ABOUT PHOTOPERIOD CANNABIS

Photoperiod strains outperform autoflowering varieties when it comes to size and productivity. They are slightly trickier to grow than autos, but the extra work is always worth it. Learn about the traits of photoperiod strains below; and check out our top 10 feminized photoperiods if they tickle your fancy! 

TOP 10 FEMINIZED photoperiods

GROWING

Photoperiod strains are deemed slightly harder to grow than autoflowers, chiefly because they require a change in light cycle to force them to flower. They also grow much taller and require more maintenance in the way of pruning and shaping.

However, growers have more control over photoperiod strains. These plants will continue to vegetate indefinitely, so long as they receive at least 18 hours of light per day. This allows indoor growers to raise huge plants before switching the light cycle to 12 hours on and 12 hours off to begin the flowering phase.

Alternatively, cultivators can grow speedy and tiny plants by starting them on a light cycle of 12 hours on and 12 hours off until harvest. This creates small plants that are easy to conceal and fast to yield.

The growing traits of photoperiod cultivars vary wildly; this is due to the genetic diversity present within the category. Botanists classify photoperiod strains into two subspecies: indica and sativa.

Overall, sativa strains achieve their full potential outdoors. Some varieties can reach tree-like heights of 3m. In contrast, indica strains grow to around 100–150cm and thrive both indoors and outdoors.

APPEARANCE

Sativa plants grow tall, feature more space between nodes, and produce fan leaves with slender fingers. In contrast, indica plants are bushier, produce more lateral growth, and feature fan leaves with broad fingers.

Mainstream cannabis culture preaches the idea that sativa plants produce an energetic high, whereas indica varieties are more relaxing. While this is true to some extent—primarily due to specific terpene profiles—it's not always the case. Morphological characteristics don't always determine the chemovar (chemical variety) of a cultivar.

Additionally, 100% pure indica or sativa strains are quite rare. Most available cannabis varieties are hybrids of both, and feature either a sativa-dominant or indica-dominant genetic profile. Strains tend to take on the appearance of whichever subspecies is more dominant in their genetic makeup.

YIELD

Photoperiod plants produce varying yields. Pure sativa and sativa-dominant strains typically pump out more flowers than indica varieties. If raised outdoors, growers can expect anywhere between 1–4kg/plant from the most productive sativa varieties. Smaller sativas produce around 500–600g/m² indoors.

Indica varieties typically churn out between 400–600g/m² indoors. Outdoors, most specimens offer anywhere between 400–2000g/plant, depending on the cultivar.

DIFFICULTY

Photoperiod strains require more care and attention. Beginners may choose a photoperiod strain for their first grow and achieve great success, but starting in the autoflowering world is a smoother entry into growing.

Growers need to plan out how long they want to veg their crop for, and prepare to change up the light cycle accordingly. They'll also need to stay on top of pruning and training to prevent their plants from growing out of control.

Some photoperiods are also capable of producing massive colas. Although this is desirable, growers need to dial in appropriate humidity during flowering and drying to avoid mould formation.

PROS

• Great production potential
• Higher cannabinoid content than autoflowers
• Greater variety of strains
• Opportunities for cloning/indefinite vegging
• More “authentic” experience

CONS

• Greater difficulty level
• Takes longer from seed to harvest
• Can be inconvenient/difficult to maintain
• Indoor growers are responsible for inducing bloom

PICK THE TYPE OF CANNABIS THAT BEST SUITS YOUR NEEDS

When it comes to choosing between autoflowers and photoperiod cannabis strains, there is no right or wrong choice. It comes down to a matter of personal preference and resources. Space is a significant limiting factor with photoperiod strains, and thus growers looking to cultivate in, say, a small apartment might be better off selecting an autoflower.

On the other hand, growers with the luxury of a big garden have the opportunity to unleash a sativa beast. However, they might instead opt for an autoflower that stays level with companion plants to keep things stealthy.

Now that you know the traits of each type of cannabis, you should feel ready and empowered to make your choice. Good luck, and happy growing!