cannabis foxtail

How To Spot And Handle Cannabis Foxtails

While foxtailing itself bears no harmful effects, it may indicate that your bud is going through a beating, and could lose a good amount of potency in the process. If it is happening in an unnatural manner, here are some ways to prevent and “treat” foxtailing in cannabis.

Growing your own bud takes a lot of time, effort, and patience. From germinating the seeds to finally harvesting the finished product, all of it takes a generous amount of work throughout quite a painstaking process.

If you are lucky, your buds will grow out how they should be: picture-perfect, in a conical shape, ready to be dried and consumed. But there are times when foxtails occur, which may add more work to the cultivation process and alter the aesthetic of your buds.


The cannabis plant features calyces, which are a potential spot for seeds to develop. Particularly for female plants, calyces grow in groups during the period of maturation when they soak up light. This presents an opportunity for foxtails to show up. Foxtails are essentially a bunch of calyces stacked on top of each other to comprise an oddly-shaped bud formation.

Buds that foxtail are not exactly detrimental, but they are not exactly beneficial either. The most glaring setback is that it breaks up the structure of the herb. Instead of growing into a rounder shape, it tends to sprout out in a more elongated way, ultimately leaving less of the plant for you to use. In addition, this process is a common indication that your plants are not properly ripening.

“Bad” foxtailing involves the occurrence of foxtails due to heat and/or light stress. This often manifests in calyces that form spires and make the bud look quite odd.

However, foxtailing is not always an abnormality. There are certain cannabis varieties that feature naturally-occurring foxtails, like in some Purple strains, or the Cole Train strain. This process is more common among sativa plants, specifically buds that were grown in tropical regions such as Colombia or Thailand.


The first type of foxtailing deals with genetics. Some buds are genetically predisposed to this process. The foxtail on these kinds of herbs is more uniform and predominant throughout the plant.

This is considered “good foxtailing” since it is already in the bud’s nature. The process will inevitably take place, no matter what growing techniques are used. It is also worth noting that buds that undergo genetic foxtailing tend to have a higher THC content.

Another type of foxtailing is caused by heat or light stress. This process usually happens to those that grow their buds indoors. Plants that are placed too close to an LED or high-powered HPS light are at the highest risk.

Unlike genetic foxtailing, which is considered “good,” this kind is the opposite. In this circumstance, the foxtailing reaction indicates that the grower must move lights further away from plants or reduce daily light exposure. Foxtails forming from light overexposure do not display much damage, but in reality, chances of the herb losing potency after repeat light stress are high.


As stated above, the cause of “bad” foxtailing is the bud’s prolonged exposure to heat and light. Common sense would, of course, dictate avoiding these occurrences, but there are other supporting methods as well.

One of them is to keep the grow room’s standard temperature at 23 degrees Celsius (74 degrees Fahrenheit) when the lights are on, then lower it 5-7 degrees cooler when the lights are off. You can do this by installing an air conditioner or venting capacity, or by going for cooled lights instead of HPS.

For the plant’s proximity to light, you can keep it at a safe distance of 24 inches under HID lights, and 30 inches under non-cooled lights. If you are using LED lights, you can go as close as 15 inches.

Another problem could be that sativa strains are more naturally suited to growing outdoors. But if you have no other choice but to cultivate indoors, be sure to limit light exposure to 11.5 hours in the span of an entire day. You can also feed it some B-52 vitamin to lower its stress levels. Allow as much space above and around the plant as possible.

With these simple steps, you could quite possibly save your yield and its potency from a stress overdose.

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What Are “Foxtails” on Cannabis Buds?

by Sirius Fourside

What to Do About Marijuana Foxtailing

Picture some dried and cured, ready-to-smoke bud in your mind. Maybe it’s some you’ve harvested yourself, maybe it’s some exotic-looking unique strain, or maybe it’s just a generic picture your mind pulls up when you think ‘weed’.

I’m sure there are a few exceptions, but I’m betting most of you didn’t automatically picture this:

Picture of a cannabis bud with a major “foxtail” coming out the top. In this case, the foxtailing was caused by too much heat, though some types of foxtails are caused by genetics.

There are new green “fox tails” near the top of this cola where the bud is too close to the grow light. On the right is a bud with a typical shape. The lower bud is far enough away from the grow light to be unstressed.

Many auto-trimming machines cut off foxtails, so if you used to purchase cannabis regularly you may have bought buds that had foxtails without knowing. That’s not necessarily a bad thing, though!

So, What Exactly Are Foxtails?

The bud we know and love is made up of a bunch of calyces (that’s the plural for “calyx”) and each calyx is a potential home for a seed. However, those seeds will only develop in cases where pollination or hermaphroditism (developing both male and female sex organs) occurs.

Buds are made up of many calyxes stacked on top of each other, but generally, buds grow evenly and stick together in bunches.

As female cannabis plants mature and soak up light, they grow calyces in groups which pile up on each other until they end up looking something like the plant above. Even the more exotic looking strains tend to form buds with a somewhat even-ish surface:

“Foxtails” are made of several calyxes stacked on top of each other in a tower-like structure.

Even when you can very clearly see each individual calyx (which is natural for some strains), they tend to be relatively symmetric, with a similar amount of “foxtailing” on all sides. (Why are these buds pink and purple?)

Another example of a strain that naturally makes foxtails in normal conditions

Foxtailing buds look a bit different from traditional buds because the calyces grow on top of each other to form spires.

These spires/towers throw off the overall shape of the bud as we’re used to, so they look odd to most people. However, there are also strains that grow bud where all (or at least the vast majority) of the calyces turn into foxtails.

Note that on these plants, every calyx is foxtailing….even the calyces on the underside! It appears to be the same action that’s happening in the “bad” foxtailing picture above, but it’s much more complete.

So, is foxtailing a bad thing? It depends…

I know, I know… no one likes an ‘it depends’ answer. A ‘yes’ or ‘no’ would be a definitive answer and it feels so nice to feel like you know something for sure! Luckily for us as growers, you can learn to tell if the foxtailing you’re seeing is good or bad in just a few minutes! Now you can impress your friends!

Note: That was a trick! Impress your friends with cooking and/or Karate, but tell no one you grow cannabis!

The Two Types of Foxtailing
(Good vs Bad)

Before we go any further, I have to admit that designating one type of foxtailing ‘good’ is a bit misleading. I call it ‘good’ in that it doesn’t provide any positive or negative benefits; ‘good’ foxtailing looks a bit funky but ultimately, it’s purely a cosmetic issue. However, ‘bad foxtailing’ really is a bad thing and comes with consequences…

Being able to tell if the foxtailing you’re experiencing is good or bad is as simple as being able to tell the difference between two foxtailing pictures. Here are two more examples side-by-side:

Let’s start with the one on the left. This type of foxtailing is caused by…

Some strains of cannabis have been bred – by humans and/or mother nature – to form buds where foxtailing is the norm. Although often foxtailing is caused by heat or light stress, when you’re growing a strain that is genetically predisposed to foxtail, the whole bud joins in on the foxtailing action. This makes it so that genetic foxtailing looks more uniform than the other type of foxtailing we’ll review in a minute.

The picture to the right is a strain called ‘Dr. Grinspoon’ (named for the esteemed cannabis activist, Dr. Lester Grinspoon). The look of this plant could be considered another manifestation of genetic foxtailing, and it’s important to note that this action happens everywhere on the plant.

Good or Bad? In short, there’s nothing wrong with genetic foxtailing. The fact that it’s genetic means that it was going to do it regardless of whatever specific growing technique is being used. These strains are also capable of containing high amounts of THC, so it doesn’t seem that genetic foxtailing reduces the potency of the plant.

This type of foxtailing is the good type. Again, that only means that it’s good by comparison to bad foxtailing in that it doesn’t cause any negative effects.

Now for the other picture. The other kind of foxtailing (the bad kind) is usually caused by…

Heat/Light Stress
The second cause of foxtailing is environmental and it’s usually caused by your lights. If you’ve ever parked a high-powered HPS or LED light (CFLs and T5s aren’t usually strong enough) too close to your cannabis, you might see it grow these odd spires.

What about when buds keep growing new white pistils over and over? This is another version of foxtailing that is caused by heat and light stress. If it’s only happening to the parts of the plant closest to the light, that’s a sign that it’s being caused by stress instead of genetics.

Good or Bad? Bad! This type of foxtailing is a sign that your buds are getting too much light and/or too much heat! These odd spires can also be accompanied by light bleaching and cooked leaves. Any one of these signs is a message that your lights need to be backed off immediately to halt any further damage. Although light bleaching and burned leaves are obviously damaged, foxtails don’t look damaged so much as they just look weird, so they don’t register as a threat to new growers. Unfortunately, they’re the harbingers of heat damage which means lost potency; if you see this type of foxtails on your buds, you’ve likely already lost potency to heat and now the mission is to lose as little as you possibly can.

Luckily, this type of foxtailing is usually localized, so you’ll only see it in spots where light intensity is super-high. This usually means they’ll be found in a small circle directly under the light, but that small circle gets larger as the light gets closer.

Now with all that being said, plants are weird! It’s totally possible that many of you growers have already seen a plant that makes the ‘bad’ looking foxtails but all over the plant. Or maybe a plant that only grows in spires! The point is that there is bound to be plants that break these rules, but at least until then you’ll know what you’re dealing with. Good luck and happy growing!

What makes long thin buds grow on top of your regular buds? And when is fox-tailing perfectly normal? Also, why do new white pistils keep appearing on almost-done buds?