Is my plant turning hermie? Pollen sacs, nanners, seeds, and how to check

By Curtis Olson — retired software developer, home grower, and the builder of the device this site is about. More about me and why I built it. · Last reviewed 2026-10-14

The short answer

• A pollen sac is a smooth, rounded ball on a tiny stalk, with no hair coming out of it. They hang in small bunches at the node, like a cluster of green grapes the size of a match head. That is a male flower. On a plant that was supposed to be female, that is the hermie.
• A female pre-flower is a teardrop with a white hair out of the top. The hair is the pistil. It browns and shrivels with age, so a browned hair on an early pre-flower is an old hair, not a sign of anything. This is the commonest “is it a hermie?” photo and the answer is no.
• A nanner is a yellow, banana-shaped anther poking out from inside a mature bud. It arrives late in flower, on a plant that is otherwise female, and it is the form stress usually takes. In the published review they can appear from about the fourth week of flower onward; a bud sprouting them everywhere is a plant telling you it has had enough.
• A swollen calyx is not a seed until you open it. Calyxes fatten as the flower matures, and unpollinated ones fatten too. Pluck one, tear it open: a hard, striped seed is a seed; a soft, hollow, sticky calyx is a flower.
• If you are not sure, wait four days and look again with a hand lens. A pollen sac gets rounder and then splits; a pre-flower grows a longer hair. Nothing is lost in four days unless the sacs are already open.

What each thing actually is

Cannabis is normally dioecious: a plant is male or female, and the female is the one grown for flower. A hermaphrodite carries both kinds of flower on one plant. Two different things get that name, and they behave differently.

• A true hermaphrodite makes male flowers — complete pollen sacs on stalks — alongside female ones, often from the first pre-flowers onward, at the nodes rather than inside the buds. That is a genetic trait of the plant or the line, and it shows early, before any bud has formed. Seeds sold as feminised are made by forcing a female to produce pollen chemically; if the parent line carries a tendency to make pollen under stress, some of its offspring will too.
• A stressed female stays female until late flower, then pushes anthers out of otherwise female flowers — the nanners. In the published work on hermaphroditic inflorescences, the anthers on those flowers split and shed pollen that germinated at only ten to thirty percent — viable, but a fraction of a male’s — and the seed it set grew into all-female plants in both strains tested. That is the mechanism behind feminised seed, and it is why a late nanner on a bud does not mean the grow is ruined: a few seeds, mostly female, not a crop of males. It also means the pollen is not harmless, as the forums sometimes say; low is not zero.
• A late-flower nanner on a plant left past its finish is the same response with a different trigger: a flower that has matured and not been pollinated makes a last attempt to set seed. It appears in the last week or two, sometimes alongside new white hairs. It is a sign the plant is done, not that it is sick.

What makes a female make pollen

The triggers growers report are the ones that stress a flowering plant, and the literature lists the same set: an interrupted dark period, extremes of heat, an irregular or lengthening photoperiod, physical damage, and simply running long past maturity. Of these the one that comes up most on the forums, and the one most often missed, is the light. A plant that gets a flash of light in its dark period every night — an indicator LED inside the tent, a timer that skipped, a neighbour’s flood light on an outdoor plant — is being told the night is shorter than it is, and a female under that signal in flower is the classic nanner plant. Heat is the other: a room that runs into the nineties Fahrenheit with the tops growing into the lamp produces the same result, and the two often arrive together in late summer. Genetics decides how much stress it takes. Some lines will not throw a single anther in a bad room; others will at the first missed timer.

Why the photo cannot settle it

Because the diagnostic feature is three-dimensional and a millimetre across. A pre-flower seen edge-on with its hair behind it looks like a ball; a young pollen sac seen from above with a leaf tip beside it looks like a bract with a hair. A phone at its close-focus limit blurs exactly the part that matters, and the picture that gets posted is the one that was hardest to take. Colour does not help either: pre-flower bracts are pale, and the browned tip of an old pistil reads as “brownish growth” to someone looking for trouble. So a thread that splits three ways — hermie, old pistils, wait and see — is not three wrong people. It is a photo that cannot carry the answer.

How to check this yourself

• Get a hand lens or a phone macro on it, in white light. Look at one node. A stalk with a ball on it and no hair is a sac. A teardrop with a hair, brown or white, is female. Look at the next node; hermaphrodites usually show more than one.
• Pluck one and open it. A sac opens to reveal yellow pollen grains or the anthers that will carry them. A calyx opens to a sticky hollow, or to a seed. Nothing on the plant is worth more than one plucked pre-flower.
• Count the days. Pre-flowers at the nodes in late veg or the first weeks of flower are the plant declaring sex; anthers inside buds from mid flower on are a stress signal, and in the last week or two a maturity one. No study fixes a week after which they are “safe”; the forum rule that late ones do not matter is lore.
• Check the night. Stand in the grow with the lights off and your eyes adjusted for ten minutes. If you can see anything, so can the plant. Do the same for the timer against a clock.
• Check the heat. A plant whose tops have grown into the lamp, in a room that runs hot, is the stressed-female case; the thermometer at canopy height is the reading, not the one on the wall.
• If it is sacs, decide by where you are in flower. Sacs at the nodes early in flower on a genuinely hermaphrodite plant: most growers pull the plant, because it will keep making them and a single open sac pollinates a room. A few nanners in the last fortnight: pick them off with tweezers as they show, finish the run, expect a handful of seeds. Everything in between is a judgement about how much you value the other plants in the room.
• Seeds from a stressed female are mostly female. That is the one consolation in the published work, and one generation of it did not measurably narrow the genetics. Seeds from a plant that made true male flowers early are a different question, and a line that does it once will do it again.

What would show that we have this wrong

If the node carries a hairless ball on a stalk and it grows and splits within a week, it was a sac and the four-day wait cost you pollen; that is why the plucked-and-opened check comes first, not the wait. And if a plant is throwing anthers in mid flower in a room that is cool, on a timer verified against a clock, in a tent walked in the dark and found dark, then the cause is not on this page and the line is the suspect.

Where our device fits, stated narrowly

Croplock does not sex a plant from a photo, and it does not tell a pre-flower from a pollen sac; that is a hand-lens job. What it holds is the two triggers you cannot check by looking at the flower: it keeps a dated record of when its light channel was switched on and off, and its camera pod’s hourly look during the dark period is logged as a dark scene or a lit one, so “was my night actually dark last week?” is a lookup rather than a memory. And it keeps the tent’s temperature at canopy height with dates, so “did it run hot in the week before the nanners?” has an answer.

Sources

• Punja, Z.K. & Holmes, J.E. (2020), Hermaphroditism in Marijuana (Cannabis sativa L.) Inflorescences – Impact on Floral Morphology, Seed Formation, Progeny Sex Ratios, and Genetic Variation, Frontiers in Plant Science 11:718. DOI 10.3389/fpls.2020.00718 — anthers on hermaphroditic flowers split and shed pollen; germination 10–30 %; seed from those flowers gave all-female progeny in the two strains tested; no measurable loss of genetic diversity after one generation of selfing.
• Richards, C.D., Ryu, B.R., Gim, G.J. & Park, S.H. (2026), Hermaphroditism in Cannabis sativa L.: Impacts, Inducers, and Industry Implications, Plants 15(11):1643. DOI 10.3390/plants15111643 — the review: genetic, hormonal and environmental causes; photoperiod disruption and temperature stress as inducers; anthers appearing from weeks 4–7 of flowering.
• Zhang, M., Anderson, S.L., Brym, Z.T. & Pearson, B.J. (2021), Photoperiodic Flowering Response of Essential Oil, Grain, and Fiber Hemp (Cannabis sativa L.) Cultivars, Frontiers in Plant Science 12:694153. DOI 10.3389/fpls.2021.694153 — critical photoperiods measured by cultivar; some cultivars responded to a fifteen-minute difference in day length.
• Ahrens, A., Llewellyn, D. & Zheng, Y. (2023), Is Twelve Hours Really the Optimum Photoperiod for Promoting Flowering in Indoor-Grown Cultivars of Cannabis sativa?, Plants 12(14):2605. DOI 10.3390/plants12142605 — flowering initiated under photoperiods up to 14 h in the cultivars tested; 12/12 is a convention, not a requirement.
• Prentout, D., Razumova, O., Rhoné, B. et al. (2020), An efficient RNA-seq-based segregation analysis identifies the sex chromosomes of Cannabis sativa, Genome Research 30(2):164–172. DOI 10.1101/gr.251207.119; and Divashuk, M.G. et al. (2014), Molecular cytogenetic characterization of the dioecious Cannabis sativa with an XY chromosome sex determination system, PLoS ONE 9(1):e85118. DOI 10.1371/journal.pone.0085118 — males XY, females XX; sex is genetically determined.
• The shape rules (ball on a stalk with no hair; teardrop with a hair; yellow anther out of a mature bud), the pluck-and-open check, the four-day wait, the tweezers-and-finish practice for a few late nanners, and the pull-it-early practice for a true hermaphrodite are grower knowledge and first-party practice, not citations. No peer-reviewed source packages the look-alikes as a field guide, and none measures a light-leak intensity or duration that triggers anthers — the papers above measure day length, not leaks.

More of these at Answers. The device is at croplock.com.

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