Fast Flowering Seeds

What are fast flowering seeds?

Fast flowering seeds, which we sell as our Fast Version line, are feminised seeds that come from crossing a photoperiod strain with an autoflower. The result is still a photoperiod plant, because it only flowers with 12 hours of darkness, but it inherits faster ripening: flowering is shorter and, outdoors, you harvest earlier than with the original strain.

It all comes down to genetics. The autoflowering trait, which comes from ruderalis, is recessive: in the first generation of the cross, the F1, it doesn't show, so the plant doesn't flower with age. What it does inherit is the urge to finish early. That's why many of these strains are sold as F1 Fast Version, and growers also call them fast flowering strains or fast flowering cannabis seeds. All of ours are feminised: nearly every plant will be female.

In practice, you grow a Fast Version like any other feminised strain: you decide how big it gets before flowering, you can prune and transplant without rushing, and you can take clones. For a side-by-side look at feminised, autoflower and regular seeds, see our guide to feminised seeds.

Our fast flowering strains, from fastest to slowest

We have 20 Fast Version strains, and 19 of them finish flowering in 8 weeks or less from the switch to 12/12. The fastest, at 45–50 days, are Skunk 1, Caramel, Mandarine Caramel and Northern Lights Fast Version. The slowest is Amnesia Fast Version, a 55–60 day sativa that is harvested outdoors in late September or early October.

“Not stated” means that strain's product page doesn't give the figure. Indoor yields are the ones on each product page; for Caramel and Mandarine Caramel, under a 300–350 W LED. Yours will depend on your light, your space and how many weeks you veg. Three more, Red California Orange, Black Zkittlez Wood and Gelato Haze Mint Fast Version, with 50–55 days of flowering, are currently out of stock.

If you grow outdoors somewhere autumns turn wet, start with the earliest to harvest: Mandarine Caramel Fast Version in early September and Cheese Fast Version in the first or second week of the month. If you're after the highest-yielding fast flowering seeds for indoors, look at Mandarine Caramel (up to 600 g/m²), Critical Green (500–600 g/m²) and Mandarine Zkittlez (450–650 g/m²). For a low grow tent, Critical Green tops out at around 100–150 cm and Jack Herer Fast Version at 80–120 cm indoors. And if sativas are your thing, Amnesia, Jack Herer, AK 47 and Banner Banana Fast Version are sativa-dominant; the fastest Jack Herer selections can finish in around 46–49 days.

How much time do you save? Fast Version vs the classic version

It depends on the strain. Comparing our own product pages, the Fast Version cuts flowering by about 4 weeks in Jack Herer and about 3 in OG Kush, but not at all in Northern Lights, which was already fast. Outdoors, Jack Herer and AK 47 go from a mid-to-late October harvest to a September one.

The rule that comes out of the table is simple: the longer the original strain flowers, the more you gain with the Fast Version. With Jack Herer, OG Kush, Amnesia and Girl Scout Cookies you save 2 to 4 weeks; with AK 47 and Skunk 1, about one; with Northern Lights, nothing. When the classic is already fast, it usually makes more sense to buy the classic, which is also cheaper (you'll see why in the price section). The Sunset Sherbet Fast Version product page gives another reference point: 6–7 weeks against the usual 8–9 for the standard version, and an outdoor harvest 1–2 weeks earlier. If you'd like to compare for yourself, these are the classic feminised versions in the table: Jack Herer, OG Kush, Super Skunk, Amnesia, Girl Scout Cookies, Tropicanna Cookies, GMO, Critical Green, AK 47, Skunk 1 and Northern Lights.

Fast Version, autoflower or classic feminised: which suits you?

If you want the shortest cycle from seed to harvest and don't mind a small plant, choose an autoflower. If you want the biggest yield per plant, a classic feminised strain. Fast flowering seeds sit in between: they're photoperiod, so you control their size and can take clones, but they finish sooner and, outdoors, bring the harvest forward to September.

It's easy to mix them up because both are sold as fast seeds, but a Fast Version is not an autoflower: keep it under 18 hours of light and it will carry on growing without flowering. If what you want is exactly the opposite, a plant that flowers on its own, you'll find all the details in our guide to autoflower seeds.

How to grow fast flowering seeds

Grow them like a photoperiod feminised strain, with fewer weeks of flowering. Indoors, give them 2 to 4 weeks of veg under 18 hours of light and switch to 12/12 when they reach between a third and half of the final height you want. Outdoors, sow in spring and, according to their product pages, most will be ready in September.

Indoors: when to switch to 12/12

Germinate the seeds as we explain in how to germinate cannabis seeds and, after one or two weeks as seedlings, start counting the weeks of veg. Many growers flip to 12/12 when the plant is around 30–40 cm tall, because it stretches during the first weeks of flowering and usually doubles in height. Some stretch even more: the Tropicanna Cookies Fast Version product page warns that it can triple in size, and those for GMO and Banner Banana Fast Version mention a noticeable stretch. Topping, LST and SCROG help you spread that growth out; if you have a good mother plant, Caramel and Mandarine Caramel Fast Version do very well in a SOG with small clones. With 2–4 weeks of veg and 6–8 of flowering, the full cycle comes to roughly 9 to 14 weeks, so you can fit several harvests into a year.

Outdoors: sow in spring, harvest in September

Sow between April and May; the Skunk 1 Fast Version product page suggests April for a mid-September harvest. Outdoors, photoperiod plants start flowering as the days get shorter, from late July or August depending on latitude. Because a Fast Version flowers for fewer weeks, it finishes in September, while many classic strains run on into October. That head start is what counts most: autumn rain, dew and cold nights encourage mould in dense buds, and fewer weeks on the plant mean less risk. That makes them the obvious choice in northern and colder climates, in the mountains and anywhere autumn storms arrive early. If you start late, in June, the plant will grow less, but it will still flower at the end of summer. For more ideas, see our pick of the best marijuana seeds for outdoors.

When to harvest: check the trichomes, not just the calendar

The weeks on each product page are a guide: phenotype, light and temperature can bring the harvest forward or push it back by a few days. To decide, look at the trichomes on the buds with a 60x magnifier. If almost all of them are clear, it's too early; the usual moment is when most are milky and a few amber ones are starting to appear, with nearly all the pistils already dark. As an example, the Mandarine Zkittlez Fast Version product page says some grows finish week eight with roughly 90% milky trichomes and 10% amber. Outdoors, if rain is forecast and the plant is almost ready, it's better to cut a few days early.

Cheap fast flowering seeds: price per seed and packs

All 20 fast flowering seeds cost the same, and the bigger the pack, the less you pay per seed: from €4.33 in the 3-seed pack down to €3 in the 25-seed pack. They're cheap because we buy and produce them in bulk, in large quantities, and there's no minimum order: you can start with a 3-seed pack.

Is it worth paying more than for the classic version? If you grow outdoors where autumns are wet, or you want a long-flowering strain such as Jack Herer or Amnesia, yes: you gain weeks. If the classic is already fast, not so much. The classic feminised versions of Northern Lights, Skunk 1, Jack Herer, OG Kush, Super Skunk, Amnesia, Girl Scout Cookies, Tropicanna Cookies and AK 47 cost €1 per seed in the 25-seed pack; you'll find them, along with many more, in cheap cannabis seeds. Curious how this works? Read our seeds vs original packs.

Buy with confidence: discreet shipping and germination guarantee

Bulk Genetics has been selling seeds since 2016, and its founders have been in the industry since 2001. We ship your fast flowering seeds in discreet packaging, free on orders over €75, well protected in aluminium zip-lock bags, and if one doesn't germinate, we'll replace it.

• Discreet shipping No logos and no reference to what's inside. We ship across Europe with tracking, and shipping is free on orders over €75. Check delivery times and costs for your country on our shipping information page.
• Germination guarantee Write to us within 30 days of receiving your order with your order number and a few photos. The terms are set out in our germination guarantee.
• Pay your way Card, bank transfer or cryptocurrency. All the details are on our payment methods page.

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Guide reviewed by the Bulk Genetics team. Updated in October 2026.