Cannabis cultivation is an intricate art that requires careful attention to many factors in order to achieve optimal yields and high-quality buds. Even the most attentive growers can experience problems, however, and foxtailing is a common phenomenon that can impact the quality and yield of your harvest. Foxtails refer to the development of elongated and airy clusters of buds that somewhat resemble the bushy tail of a fox.

Foxtails can impact the overall quality and potency of your buds, making it important to understand what foxtailing is, how to identify it, and how to prevent it.

Table of Contents


1. What are Cannabis Foxtails?


2. Is Foxtailing a Bad Thing?


3. What Causes Foxtails in Cannabis?

3.1 Genetics
3.2 Excessive Heat Stress
3.3 Light Stress
3.4 Root Zone Health
3.5 pH
3.6 Microbes


4. How to Prevent Foxtails In Cannabis Plants

4.1 Increase Airflow
4.2 Adjust Lighting
4.3 Monitor pH
4.4 Microbial Balance

What are Cannabis Foxtails?

A cannabis bud is made up of many calyces, the plural for calyx, which is part of the plant that houses the trichomes and pistils and has the function of protecting the pistils, the plant’s reproductive organs. Foxtailing occurs when one calyx forms stacked upon another instead of evenly bunched together to form a round-shaped bud.

This causes long ‘tails’ instead of packed, dense buds. These long ‘foxtails’ are typically just the width of one calyx or two and form an elongated tail about an inch or two long. Most growers prefer large dense buds rich in THC as opposed to long skinny tails of several small calyces.

Normal healthy buds are typically a tight, round shape where all calyces are joined uniformly together, however, if buds start to take the shape of a fist, un-uneven shape with protrusions, this can also be a form of foxtails. White pistils can start to grow over each other, which is also a form of foxtailing caused by heat and light stress.

Is Foxtailing a Bad Thing?

While some strains are bred to produce foxtails, most occur by accident due to stressors and are not desirable. Foxtails can reduce yield by producing long, thin irregular wisps of small calyces instead of large chunky buds. When a plant starts foxtailing due to stressors such as excessive heat and light, it can also begin to lose potency.

Foxtails occur naturally more often in heirloom sativa strains, although demand for strains prone to foxtailing is not high due to concerns for yield. If your plants start foxtailing and it is not from a genetic cause, it is important to determine the root cause of the problem to correct it as soon as possible. Foxtails are automatically cut off with auto-trimming machines, and distributors often trim them off manually; thus, you could purchase weed that has been foxtailing and not know it. If you see it happening when growing, however, you should attempt to determine the cause.

If your plant starts foxtailing towards the very end of the flowering stage, close to harvest, and you see small spurts shooting out of already formed generous buds, this is less of a concern. Some growers view this as a second internode bloom, one last “hoorah” as your plant is approaching harvest. This is often of little concern, but you should still check your grow room to make sure all conditions are still ideal.

What Causes Foxtails in Cannabis?

When growers see foxtailing in their cannabis plants, it is usually a sign that their plant is under stress and an indication to determine the cause so that it can be corrected.

3.1 Genetics

as mentioned above, some strains are prone to foxtailing, and in this case, it is not necessarily a bad thing. Cannabis strains bred to foxtail should not produce any negative or positive traits, it’s just how that strain typically grows. Foxtailing in a strain prone to it has a more uniform look than when foxtails form from stressors.

If foxtailing is occurring due to an external environmental factor, however, it should be identified and corrected to preserve as much potency and yield as possible.

3.2 Excessive Heat Stress

Cannabis prefers a consistently warm temperature throughout the entire growing cycle, and excessive heat can significantly stunt growth and limit yield. Preferred temperatures are:

  • Seedling stage: 20 to 25°C / 68° to 77° F
  • Vegetative stage: 22 to 28°C / 72° to 82°
  • Flowering stage: 20 to 26°C / 68° to 79°

If your growing room or greenhouse temperature exceeds these recommendations for an extended amount of time, it could trigger foxtailing in your plants. Lighting is a source of heat, although spikes in indoor heat and heat waves can also raise air temperature, which can have a detrimental effect on your plants. Heat can get trapped in greenhouses, and an effective airflow is required to disperse excessive hot air.

3.3 Light Stress

Cannabis plants depend on light to create the energy needed to survive and thrive. Light that is too close to your plants, however, or too intense, can create too much heat and cause foxtailing to occur. The upper buds and leaves will start to turn white from bleaching affected due to excessive lights. If you notice your leaves yellowing, this can be an indication of light stress. Yellowing leaves are also an indication of nitrogen deficiency, although in this case, they rarely wilt and will remain relatively strong. If you start to notice indications of light stress, move your lights further away from your plants immediately. You can use a light meter to measure the intensities in your grow room at different hanging heights or ask your light supplier to determine the optical sweet spot for your plants.

3.4 Root Zone Health

Environmental stress both above and below the soil can cause foxtailing in cannabis plants. Heat and light stress are easy to observe above the soil, although what’s below the surface is just as important. Healthy microbes and pH levels are extremely important for the health of plants, and if they get out of whack, it can wreak havoc on the root system.

3.5 pHh

Cannabis plants prefer a slightly acidic growing environment, and keeping your pH level between 6.0 to 7.0 is ideal. This allows the roots of your cannabis plants to successfully uptake nutrients. If your pH level fluctuates too far out of this range, the roots could fail to uptake nutrients properly, and nutrient lockout could occur. This can cause stress to your cannabis plants and trigger foxtailing.

3.6 Microbes

A single tablespoon of soil could contain 50 billion microbes which are invisible to the naked eye although are essential to create a healthy growth environment. Some species of microbes, such as fungi and bacteria, can actually help to create a more healthy root system that allows for successful nutrient uptake, although others are hostile and can wreak havoc on your root system. Parasitic nematodes, for example, can chew through roots and devour the entire structure causing extreme stress on your plants, which will turn yellow due to the lack of root system and nutrients. This stress can also cause cannabis plants to foxtail. It is extremely important to keep your soil healthy with good microbial content.

How to Prevent Foxtails In Cannabis Plants

It can be frustrating to watch your beautiful flowering buds start to foxtail. Worries of less potent pot and a less-than-desirable yield are a big disappointment. We nurture our plants from seedlings, and watching them suffer in the flowering stage is not a good feeling. Foxtailing, however, rarely causes a plant to die and mostly serves as an indication that your plants are experiencing high levels of stress. If you catch foxtailing soon enough, you can pinpoint the cause, and you should be able to correct it.

If you notice signs of foxtailing, chances are you have started to lose potency to heat damage, although all is not lost. Now is the time to act to preserve quality and lose as little as you can. If it’s early enough in the process, with many flowers still ready to bloom, you can reduce environmental stress and improve the odds of proper formation. Assuming you are growing strains not prone to foxtailing, the best approach is to return your grow room to the most optimized conditions as soon as possible.

Here are some things you can do to reverse foxtailing if caught early enough and prevent it from occurring in the first place.

4.1 Increase Airflow

Greenhouses and grow tents can quickly become overheated, especially during hot summer months. Make sure you are prepared to deal with these temperature changes with proper airflow. Use a hygrometer meter, a digital device to check the temperature in your grow space. Be ready to utilize extra fans to dissipate hot air when needed. A shade cloth can help protect plants growing outdoors from intense sun and heat.

4.2 Adjust Lighting

Adjust lighting regularly by stringing your lights up in your grow space in a way that allows you to move them around. Don’t just leave them hanging in one spot. You must continue to elevate your lights as your canopy continues to grow. Many LED grow lights have intensity lights that you can control, and you can raise the height of the light to increase the distance to the top of your plants.

4.3 Monitor pH

Regularly monitor the pH level of your soil with a pH tester at least once weekly to prevent nutrient lockout. Use pH up and pH down products to adjust accordingly to keep soil in the ideal range of 6.0 to 7.0.

4.4 Microbial balance

If you start to notice signs of a microbial imbalance, such as a nematode invasion, you should quickly implement or up your game on your pest management strategies. Consider introducing good microbes to fight off the bad microbes. Learn more in this Integrated Pest Management Guide, including prevention, suppression, and eradication and how to introduce Biological Control Agents (BCAs) to control pests naturally and reduce the use of pesticides.

Follow these tips to help prevent foxtailing and be sure to follow recommendations for the proper nutrients at each growth stage. Make sure you start your cannabis cultivation with high-quality seeds. High-quality cannabis seeds lead to high-quality cannabis plants, even if the growing conditions may not be optimal. But poor quality seeds will never produce quality plants.

Mosca Seeds is recognized internationally as a leading cannabis seed breeder, offering a wide selection of seed types and strains, including many award-winning strains. With more than 15 years of cannabis breeding experience, we offer only high-quality seeds and seeds from top-selected breeders. Check out the Seed Bizarre today and start your grow with potent weed seeds online delivered to any state.