What is the difference between autoflowering and photoperiod cannabis plants?

Why Autoflower Seeds Are Superior & The Better Choice
April 02, 2020

Light cycles play a vital role in the growth of plants. Normal marijuana strains, known as photoperiods, rely on light/dark cycles to determine when it’s time to start flowering. Once a photoperiod cannabis plant senses the days getting shorter, it knows the cold season is coming. This triggers the plant’s survival instinct and nudges it towards reproduction.

Photo = light. Period = cycle/time.

Not all cannabis strains are photoperiod. There are others that don’t rely on hours of light and dark to begin flowering. These the are auto-flowering strains. They flower after a certain time in veg regardless of light cycle, weather or season.

Where do Autoflower seeds come from?

Autoflower strains trace their lineage to a type of cannabis called Ruderalis. Sometimes referred to as Rudy, it’s indigenous to Asia and Central/Eastern Europe, specifically Russia.

Autoflower Marijuana Plant

The unique ability of ruderalis to auto-trigger its bloom phase is an adaptation to the peculiar light cycles of the high Northern hemisphere. The colder, harsher environment has produced some notable differences to sativa and indica plants.

What is a ruderalis strain?

How can you tell a ruderalis strain from an indica or sativa? How long does ruderalis take to grow? Does ruderalis produce bud high in THC? Does a ruderalis strain need darkness? Great questions! Here are some of the details that set ruderalis plants (and here we mean 100% ruderalis, NOT autoflowering hybrids) apart from their indica and sativa cousins.

  • Structure. Ruderalis cannabis plants are short and stalky. By the time they reach maturity they stand only 0.3 – 0.6m (1 to 2 feet).
  • Potency. Because ruderalis plants are small and fast-growing, they do not have time to produce THC and are neither potent nor psychoactive.
  • Growth Rate. In the time it takes some photoperiod strains to grow from seed to flowering, ruderalis are already ready for harvest.
  • Light Cycle. No property of cannabis is more unique to ruderalis than its ability to autoflower.

Breeders have taken advantage of these unique traits, developing auto-flower variants of some incredibly popular strains. Let’s answer some questions about what breeders are looking for when they create ruderalis hybrids, aka autoflowers.

Do autoflowers need darkness?

Traditional strains depend on day/night cycles to determine the season. Shorter days mean colder weather, letting the plants know to reproduce (grow attractive, sticky flower to catch pollen).

Autoflowers, on the other hand, do not share this relationship with light. They automatically flip to flowering regardless of the time of year or hours of light they receive.

How long do Autoflowers take from seed to harvest?

Because they do not depend on light cycles, autos start producing flowers after 21 to 30 days in veg. Once they start flowering, it will be a matter of weeks before they’re ready to harvest. This means their entire cycle is complete in around three months. Seed to harvest!

Harvest Autoflower Cannabis

The faster growing cycle means yields are generally smaller (per plant) than with normal, photoperiod cannabis plants. However, growers can plant autos at any time of year using the same grow lights or outdoor space, meaning multiple yearly harvests and a near-constant supply of bud.

Are autoflowering plants easy to grow?

Auto-flower strains possess the extra hardiness and resilience of the ruderalis gene. Their ability to withstand stress makes them far easier to grow than normal, photoperiod seeds.

They generally show more resistance to disease, mold and mildew and are more tolerant of newbie mistakes (like over-watering or low temperatures).

Are autoflowers less potent?

Thanks to the amazing breeders at the Homegrown Cannabis Co, our range of autoflowering cannabis seeds is just as potent as the photoperiod seeds. One of our best-selling cannabis strains is Blueberry x Jack Herer Auto at 20% THC (take a look – it’s a beautiful, beautiful cannabis plant), and you won’t struggle for a buzz from Gorilla Glue #4 Auto – this beast of a plant has a THC level of a whopping 24%!

How much room does an Autoflower need?

Autoflowering cannabis strains grow up to about 3 – 5ft. Some as low as a foot and a half. This makes them ideal for growers with a small space, or for a Sea of Green (SOG) set-up.

How can I make my Autoflowers yield bigger?

Autoflower Cannabis Plant

While autoflowers offer many advantages over traditional photoperiod strains, they do struggle to match them for yield. The shorter lifespan gives them less time to stretch and flower. If you want to increase the yield of your autoflowering plant then you should start by picking the right seed. We have a great range of high-yielding autos to choose from, with many capable of 20oz per plant and more.

Picking the right seed is step one, but there are plenty more things you can do to improve your autoflowering yields.

What size pots shall I use for autoflowers?

Transplanting autos from smaller to bigger pots can be stressful (for you AND the little auto). They do not have as much time to recover as photoperiod marijuana plants, so you’re better off putting the seedling straight into the final pot. Anything from 1.5 – 2.5 gallons should suffice.

Do autoflowers like an airy grow medium?

Autoflowers need to achieve as much growth as possible within their short lifespans. A good, airy medium helps the plants achieve optimal growth. Breathable mediums promote healthy root development and quick nutrient uptake. Some of the best choices include rockwool, perlite and vermiculite.

What’s the best light cycle for autoflowers?

Autos do not depend on day/night cycle to trigger flowering, but they still need plenty of light for growth. The best light cycle for indoor cultivation of autoflowers is 20-4 for the entire life cycle of the plant. That said, many growers blast them with 24 hours of constant light, but a short rest period certainly doesn’t do them any harm.

How do you water autoflowers?

Autoflowers should be kept well-hydrated. Over or under watering the plant, while not as damaging as it can be with photoperiod plants, will still have a detrimental effect on growth. The best way to water ANY cannabis plant is to cycle wet to dry, as championed by Kyle Kushman in his video, Feeding and Watering Your Plants.

Do you need nutrients for autoflowers?

During the very early stages of growth (young seedling), your autoflowers won’t require ANY nutrients. They won’t really need any extra food until around two weeks, even then, they won’t need a great deal. Follow the breeder’s guidelines and always, always observe your plants for signs of over or under feeding.

Can I use autos in a Sea of Green (SOG)?

Sea of Green maximizes space and light efficiency by bunching smaller plants under a single light. While it was around way before the popularization of autos, it does seem like SOG was invented specifically for autoflowering strains, being as the plant suits the method so well.

Are Autoflowering seeds worth it?

Autoflowers have come a long way. From being a wild herb struggling to survive in the bitterly-cold north, the genes of ruderalis have now spawned a new generation of easy-to-grow hybrids.

One of their biggest draws is that they allows growers to grow weed virtually any time of the year. Being just as potent as photoperiod cannabis plants, they’re a fantastic way for beginners to grow healthy, high-THC cannabis plants with the minimum of fuss.

Autoflower Cannabis Field

If there is any reason to avoid autos, it is not one that is a matter of choice. It is only because a particular strain does not have an auto-flowering seed available at the moment. Other than that, the unique traits it offers far offsets whatever benefits the photoperiod plants may have.