Just to give you an idea how small these can be when they show up… This is the exact same picture as above, but with the pre-flower made bigger so you can see it. Male pre-flowers are basically immature pollen sacs. When the plant starts flowering, they will grow and turn into bunches that almost look like grapes.
I’ve also noticed that sometimes (though not always!) the stipules on male plants seem more “leafy” and less “pointy” than stipules on female plants (the stipules are the green hair-like growths near where pre-flowers show up). However, this is just a generality, and should be used together with other factors to determine if a plant is male! There are definitely male plants with pointy stipules and vice versa, but it’s sort of a general difference. This particular pre-flower is really tough to determine. Just like the above male plant, sometimes you get almost what looks like two tiny little leaves that the pre-flower pollen sac “unfurls” from. In the above picture the pollen sac is still mostly hidden, while in this next picture, the tiny growths have opened up to fully reveal the pollen sac. This can be confusing because these extra growths don’t appear on all plants, and are not a pre-flower or a stipule. Here’s another male pollen sac pre-flower that’s on a little “stem” A single male pre-flower appears. Once you see multiple pollen sacs and no white pistils, you can be confident it’s a male plant. Although this plant ended up being male, the stipules are long, pointy and crossed as you’d normally see with a female plant.
That’s why you need to confirm sex with the pre-flowers and not just look at other factors on the plant! Sometimes the pollen sacs look a little unusual when they first start growing in, but you know it’s male when you see several pre-flowers without any pistils stacked on top of each other like bunches of grapes. If you click the following picture and zoom in close, you can see pollen sacs scattered among the leaves. This is what male pollen sacs look like when the plant actually starts flowering. This male cannabis plant has gotten further along in the flowering stage. This is what a male plant looks like at maturity when it’s starting to spill its pollen. Another example of pollen spilling onto a nearby leaf. For those who’ve never seen a male cannabis plant in its full glory 🙂 Ok, now that you know what male pre-flowers look like, what do female pre-flowers look like? Female pre-flowers tend to be longer and narrower than male pre-flowers, sometimes with a fat bottom. They also usually (but not always) have 1-2 white hairs (pistils) sticking out from the top. Sometimes it takes a few extra days for the pistils to appear. Wispy white pistils are a sure sign that you’re looking at female pre-flowers. This pre-flower doesn’t have a pistil sticking out at first, but the shape helps tell you it’s a female plant. If you’re not sure about sex after spotting a pre-flower, it’s a good idea to wait and see for a little while, just to see if a white hair appears (which means it’s definitely a girl) Another example of female cannabis pre-flowers that haven’t revealed their pistil yet. Here’s a picture that shows a pistil right as it’s emerging from the calyx! If the pre-flower is very pointy and thin like this one on the right, it is often a female pre-flower. Some of the time the stipules (green hair-like growths near where pre-flowers show up) will cross each other on female plants. This certainly doesn’t always happen, as you can see from the pics of female pre-flowers on this page, but while girls can go either way, male plants rarely have stipules that cross each other. So although crossed stipules cannot be used definitively as a way to identify female plants, it can be a small clue to help guide you when you’re not sure. For example, the following female pre-flower doesn’t have a pistil, but the long thin shape combined with the crossed stipules help indicate that this plant is a girl. This female plant has a long, thin calyx and crossed stipules, which are typical female plant features. In this pic, you can see white pistils emerging from the calyxes. Here’s another female pre-flower that doesn’t have a white hair yet, but you can tell it’s female because it’s long and narrow, instead of spade-shaped. The long narrow shape is the only thing that gives the sex away until pistils begin to emerge. Super close-up picture of a female cannabis pre-flower. Female cannabis calyxes with pistils, under an LED grow light. Did you know that pre-flowers/calyxes/flowers are actually what holds seeds if your plant gets pollinated?
Once pollen touches the white pistils, the pollen gets delivered to the inside and a seed starts forming! Variability of Cannabis Plant Sex – How to Increase Ratio of Female Plants with Regular Seeds. In fact, to this day scientists are still not sure exactly what causes certain plants to be one sex or another after sprouting. We’ve identified several factors that predict the overall likelihood of male/female plants (for example feminized seeds always produce female plants no matter what), but sex seems to be somewhat fluid in cannabis plants when they’re first germinated. Certain conditions such as excessive heat, stress, unusual light periods and nutrient problems can cause a greater percentage of plants to produce male flowers. You may be able to increase the percentage of female plants with regular seeds during the first few weeks of life. On the flip side, the following factors may possibly increase the ratio of female plants with regular seeds (learn more): Healthy Mom – Only grow seeds from a vigorous, healthy mother plant who never showed any signs of herming or male pollen sacs (seeds are more likely to grow pollen sacs if the mom plant had a tough start in life, or hermed during the flowering stage) Cool Temperatures – Give seedlings slightly cool temperatures (65-75°F day and night) and avoid excessive heat High Humidity (50-70% RH) Short but not too short days. Keep consistent day and night periods with no light interruptions at night, and days should be 14-18 hours long (between 14/10 and 18/6) for the first few weeks Blue light.
Always start seeds under a vegetative grow light (something with plenty of blue like a Metal Halide or a 6500k CFL/T5/fluorescent) Avoid Deficiencies – Make sure to provide plenty of Nitrogen and don’t let seedlings become nutrient-starved or run into other types of deficiencies Prevent Stress , especially heat or light stress during the first few weeks Happy Roots – Avoid over (and especially) under watering. Once a cannabis plant is about 3 weeks old, its sex is pretty much completely set and can be determined either by visual inspection or by chemical leaf test. Unfortunately, due to the fact that different environmental conditions during the first part of life can alter the sex, you can’t look at seeds and definitively know one way or the other whether the plant will end up being female because even the plant doesn’t necessarily “know”. For example, say you take a clone of a seedling before it’s 3 weeks old. It’s possible that one clone will be male, and the other clone will be female.