How to Prevent, Detect & Manage Hermaphrodite (Hermie) Marijuana Plants

Marijuana plants usually grow into male or female versions.

Unfortunately, some cannabis plants that have female flowers also develop primitive male floral structures that pollinate female buds on the same plant and other plants nearby.

These sexually confused plants are called hermaphroditic (or hermie), and they’re a plague in the marijuana industry because hermies give you seeded buds when you wanted unseeded ones.

As you know, we rigorously research seed breeders and test dozens of seed and clone strains per year. We’re sad to report that more and more seed companies are selling crappy seeds with hermie traits on board.

It’s an epidemic of hermies!

Hermaphroditism embedded in a strain’s genetics is the result of unprofessional breeders with low standards.

These breeders tell you the reason your flowers developed hermie clusters is because you did something wrong in your grow op. This is just an evasion. If they’ve rigorously excluded hermie traits during their strain creation process, you won’t get hermie buds no matter how harsh your grow op is.

There are too many situations when we have the perfect grow op, with most of the strains NOT developing hermie problems, but others do.  That’s proof that the grow op is not at fault. It’s the breeder, who may have seen hermie traits in the strains during the breeding process, but decided to sell them anyway.

I’ve seen many breeder websites with casual warnings that some of their strains might go hermie. It’s crazy that they expect us to buy those strains.

Strains with hermie genetics don’t always develop hermie clusters. But when conditions get too far away from ideal, the trait is triggered.

If you fix your growing procedures and grow op environment, you might block hermie clusters from showing up. But hermie strains often go hermie regardless of how wonderful your grow op is.

It helps to know exactly what you’re looking for—so take a close look at the main photo for this article of a plant 21 days into bloom phase.

The top half of the photo shows white pistils and other structures normal for an unpollinated 100% female flower.

The bottom half shows male floral clusters that have already broken open and dispensed pollen that seeded female flowers on the hermie plant and buds of other plants.

It’s very important to note this photo shows one of two configurations of a hermaphroditic plant’s floral structure.

This type of hermaphroditism consists of fully-developed female and male floral structures on the same plant. In this type, the male floral structures look the same as if you had a 100% male plant.

Male and female floral structures in this type of hermie plant are usually separated from each other (as shown in the photo).

There’s normal female bud above; below it (sometimes separated by a stalk node or at least 1/8th inch or more distance), you see fully-developed male flowers.

The second type of hermie floral structure is more sinister and harder to detect because solo or small bunches of male pollen sacs develop amidst female floral structures.

These structures are very difficult to see because they might not be as tall as the female bud’s white pistil hairs.

Sometimes they’re embedded deep inside a thick female bud so you can’t even see them from the surface. You only find out you had hermies when you dry and consume the buds…and find seeds in them:(

The following photo shows this second type of hermie structure. Growers call those little lime-yellow things “hermie nanners.” It’s a slang term for hermaphroditic structures that look like tiny yellow or light green bananas, hence the word “nanners.”

Nanners are usually no more than 1/16^th to 1/8th inch long, and can appear singly or in clusters. Clusters of nanners look like a miniature stalk of bananas on a banana tree.

Take a look amongst the white pistil hairs slightly to the left of top-center in this bud photo, and elsewhere, and you’ll see the dastardly nanners!

Nanners (officially called “stamens”) don’t always fully develop into structures like flowers on 100% male marijuana plants, but still dispense enough pollen to seed buds.

An important difference between fully-developed hermaphroditism and nanner hermaphroditism is that a primarily female plant with a significant number of fully-developed male flowers is most often caused by inherent genetics, not just plant stress.

Indeed, hermie genetics strains develop male and female flowers on the same plant even in the best grow room conditions.

In contrast, nanners are mostly caused by plant stress and other unfavorable conditions. Genetics plays a role, of course, but they have to be triggered by bad growing conditions.

When a grower is confronted with the type of hermie plant shown in the main article photo, the grower can be pretty sure the plant’s genetics are wholly defective.

Plants that only have nanners may revert to 100% female floral structures when plant stress is eliminated, especially during early bloom phase.

The bottom line is: when you have a multi-strain grow room, with all plants experiencing the same conditions, and only one or two strains develop hermie traits, the strain has hermie genetic tendencies and is to be avoided at all costs.

It’s worthless to grow hermie genetics again, or to breed with the seeds they produce, unless you want to spend hours with a magnifying glass and tweezers, removing nanners or male flowers, hoping that pollen won’t create seed buds despite your removal efforts.

WHAT CAUSES HERMAPHRODITE MARIJUANA?

Several things cause hermaphroditic cannabis flowers:

• Genetics: Some cannabis strains, especially pure or dominant Sativa, naturally develop hermie flowers, and the breeder didn’t have the sense to eliminate those traits during breeding. Hermaphroditism is  a female marijuana plant’s attempt to supply pollen to itself when none is coming from male plants. Genetic hermie traits are also caused by unskilled breeders attempting to make feminized and/or autoflowering seeds, and by other breeding and seed creation mistakes.
• If you leave marijuana plants in bloom phase “too long,” some strains create hermie clusters. If you have robust resin glands and are in last week of bloom phase when hermie features show up, test a bud to see how potent it is, and consider harvesting those plants before seeds have time to develop. It takes at least 1-3 weeks for seeds to mature, so if you see a few hermie features just before harvest time, let those plants grow until harvest in a quarantined grow tent, ensuring their pollen won’t pollinate other plants that have a longer time left before harvest.
• Excessive High-Intensity Light: Especially when you’re using LED grow lights, it’s easy to overdose plants with light radiation without visibly burning their leaves. Using a professional light meter intended for LED grow lights, such as those made by Apogee, you’re looking for PPFD readings of about  400-600 during bloom phase in a grow room without added C02. More light than that may stress plants, which could cause hermie traits to emerge.
• Note also that hermie flowering can be triggered when grow lights are too close to plants, creating excess bud heat and leaf temperature. Using a digital directional thermometer, monitor your leaf surface temperature and keep it under 87°F. Preferably, leaf surface temperature should be 76-86°F, depending on whether you’re adding C02 to the grow room or not.
• Irregular light cycles or light leaks: You want bloom phase photoperiod indoor marijuana plants in a timer-driven grow op that starts and ends the 12-hour bloom phase lights-on cycle at exactly the same time every day. You want zero light leaks. Even tiny amounts of light, such as the faint glow from a power strip or infrared glow on a security camera, can interrupt bloom phase dark cycle and create hermaphroditism and other problems. Light cycle problems aren’t seen as often in autoflowering plants, which flower on their own and have less need for a specified dark period.
• Root zone stress: Overwatering, underwatering, incorrect nutrients and/or root zone pH, overfertilizing, underfeeding, inferior root zone substrate management, root zone pathogens and other problems create stress that can lead to hermie flowers.
• Environmental stress: If grow room temperatures, relative humidity, vapor pressure deficit and other environmental conditions are harsh for your plants, stress from that can cause hermie flowers. If your marijuana plants are under attack from pests, gray mold, powdery mildew or other attackers, the resultant stress can trigger hermaphroditic flowers.
• Unsafe cultivation practices: Stressing plants by pruning too much or severely pruning/lollipopping after bloom phase has started are examples of cultivation practices that cause hermie flowers.

Detect and Prevent Hermie Marijuana From Happening to You!

Now let’s take a look at how to prevent and detect and hermie marijuana plants:

• Before buying specific strains in seed or clone, query breeder about hermie traits. Research seller/breeder/strain to see if there are any online reports of hermaphroditism.
• Landrace strains, pure Sativa strains, and feminized photoperiod strains tend to develop hermaphroditism way more than hybrid strains, non-feminized strains, and mostly Indica/Kush genetics.
• Strains that breeders specify as meant for outdoor cultivation sometimes develop hermaphroditism when you grow them indoors, and vice versa.
• Ensure that your grow op cultivation procedures (watering, feeding, lighting, climate control, C02, air movement) and environment are ideal. Subjecting your plants to too much light, heat, C02, or nutrients is an example of how you create stress that can cause flowers to go hermie.
• Avoid pruning after the first week of bloom phase.
• Block pests and diseases from your grow room. They create stress that can trigger hermaphroditism.
• Make sure your bloom phase light cycle timing is 100% consistent, with no deviation from grow light start and stop times, and no lights leaks or other interruption of the lights-off period.
• Closely examine your plants beginning at the start of bloom phase, using the photos and the video in this article as guides so you immediately detect hermaphroditism as soon as it occurs.
• Sometimes, if bud hairs turn orange or brown too early in bloom, it’s a sign that hermie pollen exists in those buds and has pollinated them.
• Use a magnifying glass or jeweler’s glasses (which have magnification built into the lenses). Not only are you looking for male floral clusters and nanners, you’re looking for pistils that used to be snow white but are suddenly turning brown or red–a sign that pollen has fertilized those buds. Unless you have male marijuana plants nearby, there’s only one place the pollen came from: hermie clusters.

Managing Hermie Marijuana Plants

What to do if you see nanners or male floral clusters on your female marijuana plants? Your tactics vary depending on your grow room set-up, when in bloom phase you detect the hermie structures, and what crop outcomes you can tolerate. Here are some case studies that offer strategy tips:

Case Study A: The grower had a normal bloom phase until the last two weeks of an expected 9-week duration, when he first saw nanners in a few female buds. He saw no brown pistils or seed development. Knowing he’d be harvesting soon, he did nothing. He harvested the buds and when grading them discovered no seeds had formed. Lucky!

Case Study B: The grower saw nanners early in bloom phase on two plants from the same strain in a mixed-strain grow room.

He made sure his grow room environment and plant inputs were optimized, spent a half hour per day inspecting plants for signs of pollination, and used tweezers to pluck off all nanners and the tiny parts of buds that showed pollinated pistils.

After initial removal of all nanners, one plant never developed nanners again. He successfully harvested large, potent, unseeded buds from this plant.

But the other plant continued to develop new nanners.

The grower put it outdoors and let it grow until it was ready to harvest. The buds were partially seeded, but resinous and tasty. He used those hermie-seeded buds to make extracts.

Case Study C: A grower was cultivating pure Sativa genetics. The strain breeder had warned the grower about possible hermaphroditism starting in the middle of bloom phase.

At 10 weeks into an expected 13-14 week bloom phase, male flowers developed.

The grower isolated the hermie plant in a grow tent, and plucked the male flowers off on a daily basis. He lightly sprayed the affected stalks with water, because water is known to disable pollen, not just wash it away.

He harvested about a week earlier than he’d have preferred, and found the buds to be potent, tasty…but about 35% seeded. The unfortunate thing is that other plants in the grow room were also partially seeded by the hermie pollen, and that seeds produced by hermie pollen carry the hermie trait.

Case Study D: A grower was manually controlling his bloom phase lights on and off, rather than using an automatic timer, and doing a poor job of it.

His light control timing was so inconsistent—his poor cannabis plants were stressed by varying lengths of light and dark per day.

They developed nanners in week three of bloom phase.

We advised the grower to put his lights on a timer and ensure a strict 12 hour on/12 hour off formula, with the same start and stop time each day.

He removed the nanners for seven days as the plants got used to the predictable light cycle. Then, his plants stopped producing nanners and were 100% female until harvest.

His harvested buds were only 3-5% seeded. In subsequent grow ops, the same strain was grown; without light cycle stress, no nanners were observed.

As you can see, serious marijuana growers work hard to detect and stop hermie structures from seeding their buds. They’d rather not have to get rid of a bloom phase plant if they can avoid it.

However, to be 100% sure you won’t end up with a seeded grow op, the best strategy is to get only the best genetics. And get rid of hermie plants immediately, making damn sure non-hermie plants in the same proximity haven’t been seeded.

As you know if you read this magazine frequently, we have extremely high standards for marijuana seeds and strains, and only recommend a few of the hundreds of marijuana seed sellers worldwide.

During 25 years of professional testing, we’re seeing more hermies rather than less, and mostly in feminized seeds.

And other than Serious Seeds and Pure Breeding Seeds, every other seed company we’ve tested, including some we have written articles about here, have recently sold us seeds which grew out hermie. Not all of their strains, but enough to make us doubt their professionalism and integrity.

This includes some of the most famous, or best-advertised, seed sellers, such as Sensi Seeds, Barney’s, Green House Seeds, Rare Dankness, Cali Connection, Humboldt Seed Organization (HSO are total scammers) and others you’ve probably heard of.

When we sent photos of their strain’s hermie buds to one of these companies, they whined that it was impossible it was their strain, blamed our grow ops, claimed they’ve never had anyone else complain about hermie problems in their strains.

That was easily proven to be a lie when we put their company name and the word hermie into a search engine and found many cultivation forum threads complaining their strains go hermie and otherwise suck.

We shared that thread with them, but all they did was lie and do pushback.

If you want to be sure of not having hermie strains, buy strains only from Serious Seeds.

We wish there were more seed companies whose strains have never gone hermie on us, but Serious Seeds is the only seed company out of the more than 275 we’ve tested whose strains have never once gone hermie.

Please watch the following fantastic video to get more understanding of hermaphrodite marijuana!