A Home Grower’s Guide to Cannabis Seed Labels

A cannabis seed listing can read like a page of lab notes. One product might list its genetics as Dirty Mimosa Bx2 x Sour Moose F1, followed by a seed type, a growth type, a flowering window, and a rating for phenotypic variation.

Each of those details answers a practical question. Together they tell a grower how the plant decides when to flower, how many seeds will turn out female, and how much the plants in a single pack will differ from one another.

The shorthand is often the steepest part of the learning curve for new growers, and it still trips up veterans because breeders do not always use terms the same way. This guide breaks down the vocabulary that appears most often on seed menus, with examples from North Atlantic Seed Co. (NASC), a Maine seed shop that carries more than 65 breeders alongside its in-house line, Dirty Bird Genetics.

Autoflowers vs. Photoperiods

Growth type is usually the first split on a seed menu, and it determines what tells a plant to start flowering.

Photoperiod plants, or photos, flower in response to light. Indoors, growers trigger flowering by switching the lights to 12 hours on and 12 hours off, a schedule often written as 12/12. Outdoors, the shortening days of late summer do the same job.

That control is the main appeal of photos. A grower can keep a photoperiod plant in vegetative growth for as long as the space allows, which makes photos the standard choice for training, cloning, and keeping mother plants.

Autoflowering plants, or autos, start flowering on their own after a set period of growth, regardless of the light schedule. The trait comes from Cannabis ruderalis, a type from regions with short growing seasons, which breeders have crossed into modern genetics. Autos tend to be compact and fast. In autoflower growing notes published on NASC’s blog, breeder Mosca Seeds puts the start of the harvest window at about 70 days for many modern autos under good conditions, and recommends 18 to 20 hours of light a day indoors once the plants are established.

The tradeoff is a short vegetative window with little room for error. A stressed or root-bound auto cannot be given extra vegetative time to recover the way a photo can, and NASC’s guide to seed types notes that autos make poor candidates for cloning, since cuttings flower on the same clock as the plant they came from.

One more label adds to the confusion. Strains marked “fast” or “fast flowering” are still photoperiod plants that need a light change to flower; they simply finish sooner than a typical photo.

Growth type and seed type are separate choices, and both autos and photos come in feminized and regular versions. Purple Lemonade Auto from Fast Buds, for example, is listed as a feminized autoflower.

Feminized vs. Regular Seeds

Seed type describes how a seed was made, and it sets the odds of getting female plants. Only female plants produce the flowers growers harvest, and pollen from a male plant will fill those flowers with seeds.

Regular seeds, marked (R) on NASC’s menu and often called regs, come from a natural female pollinated by a natural male. A pack typically produces about half males and half females, so growers aiming for seedless flower plant extra seeds and remove the males once the plants show their sex. Growers who want to make their own seeds often prefer regs because they include males.

Feminized seeds, marked (F) on NASC’s menu and often called fems, come from a female plant pollinated with pollen from a female that has been induced to produce it, a process known as reversal. The pollen donor can be a second plant or the same plant. With no male parent in the cross, nearly every seed grows into a female plant; NASC puts the figure at 99.9 percent. That saves the time and money of growing out males only to discard them.

Neither type is immune to hermaphroditism, in which one plant grows both male and female flowers. According to NASC, poor care in the garden or poor parent selection by the breeder can cause it, so regular checks through flowering are good practice with any seed.

F1, S1, Bx and the Rest: Breeding Generation Labels

Generation labels describe a seed’s family tree, which hints at how uniform the plants in a pack will be. The F stands for filial, meaning offspring, and the system comes from formal plant breeding.

Cannabis breeders use the terms more loosely than botanists do. Most cannabis parents are hybrids themselves rather than pure, stable lines, so a label describes ancestry more than it guarantees consistency. With that caveat, here is how the common labels break down, following the definitions NASC uses in its guide to cannabis labels.

Labels still vary from breeder to breeder. Many companies use F1 for any first-generation cross, feminized or not, which makes R1 the more specific of the two terms. In an interview with Compound Genetics, the breeder described R1 as the feminized equivalent of an F1. When a label is unclear, the breeder notes on a listing usually fill in the details.

Putting It Together: Reading a Real Listing

A recent Dirty Bird Genetics release shows how the labels work together. The listing for Amaretto Sour gives its genetics as Dirty Mimosa Bx2 x Sour Moose F1.

Reading left to right, the first parent is Dirty Mimosa Bx2. Dirty Mimosa descends from the Brunch, Dirty Bird’s cross of Peanut Butter Breath and Mimosa, crossed back to Mimosa, and the Bx2 tag marks a second backcross generation. The second parent, Sour Moose F1, is a first-generation cross of Sour Lime Haze and Moose n Lobsta. According to the breeders, both parents were keeper plants selected from Dirty Bird’s own seed runs.

The rest of the listing covers the practical details:

• Seed type: Feminized
• Growth type: Photoperiod
• Filial generation: F1
• Flowering time: 55 to 65 days
• Phenotypic variation: Moderate

A moderate rating means a pack will likely produce more than one distinct plant type. The breeder notes for Amaretto Sour describe about half the plants leaning toward each parent, which helps a grower decide how many seeds to start.

Two more terms appear on listings like this one. A cut is a specific plant selected from a seed population and kept alive through cloning; Candy Apple Kush, for example, names Bad Apple (Sugar Mill Cut) as one parent. Keeper numbers such as #5 or #8 identify individual plants chosen from a breeder’s test run.

For quick comparison, here is how four strains on NASC’s menu read:

Strain	Breeder	Seed type	Growth type	Label worth noticing
Purple Lemonade Auto	Fast Buds	Feminized	Autoflower	“Auto” in the name signals the growth type
Acapulco Gold	Barney’s Farm	Feminized	Photoperiod	“(F)” in the product name marks it as feminized
Candy Apple Kush	Dirty Bird Genetics	Feminized	Photoperiod	A named cut as a parent; listed at 50 to 60 days of flower
Amaretto Sour	Dirty Bird Genetics	Feminized	Photoperiod	A Bx2 parent and an F1 parent in one cross

What a Curated Seed Shop Adds

Labels describe a seed’s genetics, but not the track record of the breeder behind it. A curated seed shop helps fill in that part of the picture.

Founded in 2019 and based in Fairfield, Maine, NASC carries more than 65 breeders. Its menu sorts strains by practical goals, with categories such as Beginner Friendly, Early Finishers, Outdoor Seeds and Stabilized Genetics. Listings for strains from its in-house line include notes from the growers and breeders who tested them, covering structure, stretch and how the plants behaved in flower.

The shop’s in-house line, Dirty Bird Genetics, documents its breeding work in public. Owner Beth Mathieu has written a multi-year account of developing the Brunch, Dirty Bird’s flagship strain, from an F1 toward a stable inbred line, which doubles as a case study in the labels above.

For growers shopping for someone else this season, NASC’s Holiday Collector’s Boxes, a collaboration with many of its most popular breeders, are scheduled to drop on October 31. Seed laws vary by state, and growers should confirm their local rules before buying or germinating seeds.

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Images courtesy of North Atlantic Seed Co.

Sponsored Disclaimer: This article is sponsored content produced in partnership with North Atlantic Seed Co. Product specifications, flowering times, the 99.9 percent female rate for feminized seeds, breeder and grower notes, growing guidance published on its blog, the company’s breeder count and founding date, and details of its Holiday Collector’s Boxes and Keep Seeds Legal campaign were provided by or drawn from North Atlantic Seed Co.