An autoflowering seed grows into a cannabis plant that starts flowering on its own, based on age rather than on changes in its light schedule, thanks to genes from Cannabis ruderalis. Autos (as growers call them) flower a few weeks after sprouting no matter how many hours of light they get, so they need a different game plan than photoperiod feminized seeds.

How are autoflowering cannabis seeds made?

Autoflowering seeds come from crossing photoperiod-dependent cannabis plants with ruderalis genetics.

So what is Cannabis ruderalis?

Cannabis ruderalis is a subspecies of hemp native mainly to cold regions like Eastern Europe, Central Asia and other areas with climates that are clearly rough on cannabis. It's known for being short and low in THC, and above all for its ability to flower automatically regardless of how much light it gets.

The result of that cross is a plant called an autoflower, which starts flowering somewhere between its second and fourth week of growth, regardless of its light cycle (photoperiod).

That's one of several reasons so many autoflower seed banks and seed breeders have focused on developing autoflowering strains.

Autoflowering is a unique and fairly rare trait. It happens when breeders working with the widely grown Cannabis indica or sativa strains bring in Cannabis ruderalis genetics.

Pure indica and sativa strains depend on photoperiods (changes in the ratio of light to dark hours they're exposed to) to flower, while ruderalis strains almost never do.

Pros of growing autoflowers

• Autoflower seeds give outdoor growers fast, easy harvests. They also let you run whole autoflower crops while your photoperiod plants are still vegging or flowering. In Argentina, growing autos outdoors legally is possible through REPROCANN, the country's medical cannabis registry.
• They stay small (about 1 m / 3 ft tall at most), which makes autoflowering seeds very discreet for outdoor grows on rooftops, balconies or patios.
• If your climate allows it (nighttime lows always above 10 °C / 50 °F), you can grow autos outdoors year-round.
• Because their life cycle is short and fast, they're exposed to pests for less time.
• If you grow autos outdoors, you'll notice they handle cold better, although they still prefer mild climates.

Cons of growing autoflower seeds

• Indoors, fast-flowering feminized photoperiod seeds can match an autoflower's grow time, and the photoperiods usually give you better quality and bigger yields.
• Because they don't respond to the light cycle, you can't keep autoflower genetics going, which means no mother plants and no clones.
• Autoflower seeds tend to produce fewer cannabinoids than the photoperiod version of the same strain.

How to germinate autoflower seeds

Germinate the seed:

You'll need a germination method and a seed, like the ones in our shop (Argentina only).

Prep your containers:

Once your seeds have germinated, have some small 7 × 7 cm (about 3 × 3 in) pots ready with soil, so the root can grow without obstacles. Ideally, avoid starting them in Jiffy pellets.

First, fill the pots with soil and water them thoroughly, because you won't water again until the seedling breaks the surface. If you water before the seed pops up, it can shift, float to the surface, end up buried too deep, or burn when it emerges into soggy soil.

Plant the seed:

Plant the seed half a centimeter to 1 cm (about ¼–⅜ in) deep, poking a hole with a pen or something similar. Drop the seed in with the root facing down, cover it with a little soil without packing it down, and leave it until it finally breaks the surface.

Ideally, give them 24 hours of light during this stage until you transplant them into their final container. If you don't have a grow light, give them as much light as you can and keep the pot from getting cold.

Now wait:

Wait for it to come up and do that classic stretch cannabis seedlings do as they reach for the light. That takes about four or five days, not much more, and you need to keep a close eye on it so you don't leave it too long. Don't let the plant start settling into that tiny pot.

Move them to their final container:

Fill your final container to the top with soil, settled enough that it doesn't sink too much when you water. Pack it too tight and there won't be enough oxygen for healthy roots. Firm it just right; you'll get a feel for it with time. Ideal light is 20 hours a day until the end, or as many hours of sun as you can get.

Once the final container is full, dig a hole for the plant from the small pot. Make it deep, since you'll bury it stem and all. Next, water slowly around the edges so the soil gets soaked through.

What pH do autoflowers need?

Soil pH determines how well your plants can absorb the nutrients in it. If the pH is too high (alkaline) or too low (acidic), you can get nutrient lockout and deficiencies. Cannabis does best in soil with a pH between 6.0 and 6.5.

Best growing medium for autoflowers

Choose a good, well-aerated, quality growing medium for your autoflower seeds.

Most potting soil already contains coco coir, but you can add more (30–50%) to give the mix extra aeration.

You can also grow straight in coco, but remember coco is an inert medium, so you'll need to feed from the very start.

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