Banana Pollen Sacs (Nanners): Identification and Handling
How to spot, isolate, and respond to banana-shaped male flowers on otherwise female cannabis plants before they seed your crop.
Nanners are bare stamens that pop out of female flowers when a plant is stressed or genetically unstable. Unlike normal pollen sacs, they release pollen almost immediately — sometimes within hours of appearing. There's no clever trick that makes them harmless. You either catch them early and remove them, isolate the plant, or accept seeded bud. Most 'cures' you'll read on forums (spraying with water, silver-based reversal sprays at this stage) are either folklore or actively counterproductive late in flower.
What a nanner actually is
A 'nanner' is a single banana-shaped stamen (the male pollen-bearing organ) that emerges directly from a female flower, without the protective calyx-like sac that surrounds normal male pollen sacs. The name comes from its curved yellow shape.
Cannabis is normally dioecious — separate male and female plants — but it can express intersex (monoecious) traits under stress or due to genetics [1][2]. There are two visually distinct forms of intersex expression:
- True pollen sacs: round, grape-cluster-shaped structures that develop over days and release pollen on a predictable timeline. These look like male flowers.
- Nanners: exposed anthers with no sac. They can shed pollen almost immediately on emergence Strong evidence[2].
That second point is what makes nanners urgent. By the time you see them, viable pollen may already be in the air.
Why nanners appear
Nanners are a stress or genetic response. Documented and well-supported triggers include:
- Light leaks or interrupted dark periods during flower Strong evidence[1][3].
- Heat stress above roughly 30 °C / 86 °F at the canopy Weak / limited[3].
- Late harvest — plants past peak ripeness often throw nanners as a last-ditch self-pollination strategy Weak / limited[2].
- Physical damage, severe defoliation, or root problems late in flower Weak / limited[3].
- Unstable genetics — some cultivars hermie under conditions another phenotype shrugs off Strong evidence[2][4].
The popular claim that 'feminized seeds always hermie' is folklore Disputed. Properly produced feminized seeds from stable parents are no more prone to intersex expression than regular seeds; poorly produced ones absolutely are [4].
When to start looking
Begin daily inspections from week 3 of flower onward, and increase frequency in the last three weeks before harvest, which is when nanners most commonly appear.
Inspect with a bright light at lights-on, before any disturbance. Focus on:
- The main cola tips and the inside of dense bud sites.
- Areas closest to heat sources or light leaks.
- Plants that have already shown any stress (yellowing, wilting, recovery from a knockover).
Use a 10x loupe. Nanners are small — often 3–8 mm — and tuck between calyxes. A naked-eye scan misses early ones.
Step-by-step: handling a nanner sighting
1. Don't panic and don't shake the plant. Pollen disperses on air currents. Move slowly.
2. Turn off fans. Kill oscillating fans and any active intake/exhaust if possible. You want still air for the next few minutes.
3. Photograph and assess. Confirm it's a nanner and not a swollen calyx, a stipule, or a pistil tip. A loupe helps. Note how many you see and on how many plants.
4. Bag before you cut. Bring a small zip-top bag to the nanner. Slide it over the bud site, then snip or pluck the nanner inside the bag. This traps loose pollen. Don't pluck in open air.
5. Seal and remove. Close the bag, take it out of the room, and dispose of it outside the grow space. Wipe your scissors with isopropyl.
6. Decide on the plant. Count what you find. A single nanner on one bud near harvest is usually manageable — keep inspecting daily. Multiple nanners across multiple sites means the plant is committed to intersex expression and will keep producing them. Options:
- Isolate: move it to a separate space if you have one.
- Harvest early: if you're within ~10 days of your target chop, pulling now often beats letting it pollinate the rest of the room Weak / limited.
- Cull: in a multi-plant room with valuable genetics, removing one plant can save the others.
7. Find the trigger. Check timers, look for light leaks with all room lights off, verify canopy temps, inspect roots. If you don't fix the cause, expect more.
8. Wipe down. After harvest, clean surfaces with damp cloths before bringing in the next round. Pollen stays viable for weeks to months in dry conditions Strong evidence[2].
Common mistakes
- Spraying nanners with water to 'kill the pollen.' Water can burst already-dehiscent anthers and spread pollen. If you spray, do it gently and only after bagging.
- Using colloidal silver or STS late in flower. These are reversal agents used early in flower to induce male flowers for seed production. Applying them mid-flower to 'fix' a hermie does nothing useful and contaminates the buds you'd smoke Strong evidence[5].
- Ignoring a 'just one' nanner. A single nanner can pollinate dozens of nearby flowers. Seeded weed isn't unsafe, but it's lower quality and lower yield in usable flower.
- Plucking in open air. This is the single most common way to seed a whole room.
- Blaming genetics first. Most nanner events in home grows trace back to a light leak or a timer fault, not the seed bank.
- Continuing to run a known hermie line. If a cultivar throws nanners across multiple grows under clean conditions, the genetics are unstable. Replace the stock.
Related techniques and topics
- Light Leaks in Flower — the most common preventable cause.
- Feminized Seeds: How They're Made — context on STS and colloidal silver reversal.
- Harvest Timing — late harvest is a common nanner trigger.
- Intersex Cannabis Genetics — deeper look at the biology.
- Pollen Collection and Storage — if you want pollen, the same biology works in your favor.
Sources
- Peer-reviewed 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.
- Peer-reviewed Small, E. (2015). Evolution and classification of Cannabis sativa (marijuana, hemp) in relation to human utilization. The Botanical Review, 81(3), 189–294.
- Book Cervantes, J. (2015). The Cannabis Encyclopedia: The Definitive Guide to Cultivation & Consumption of Medical Marijuana. Van Patten Publishing.
- Peer-reviewed Lubell, J. D., & Brand, M. H. (2018). Foliar sprays of silver thiosulfate produce male flowers on female hemp plants. HortTechnology, 28(6), 743–747.
- Peer-reviewed Ram, H. Y. M., & Sett, R. (1982). Induction of fertile male flowers in genetically female Cannabis sativa plants by silver nitrate and silver thiosulphate anionic complex. Theoretical and Applied Genetics, 62(4), 369–375.
How this page was made
Generation history
Drafting assistance and fact-check automation are used, with a human operator spot-checking on a weekly basis. See how articles are made.