Growing cannabis requires patience and effort, even though crops do not always go the way we wish. This is due to different phenomena, such as cannabis foxtails which gives the plant a strange but pretty appearance. Cannabis foxtailing is not always bad and not a cause for real concern, sometimes it’s just because of genetic factors. In fact, difficulties can appear if it’s environmental stress which produces them.
Foxtails: what are they?
Phenotrigo in marijuana occurs when, in the flowering stage, plants begin to develop buds in a stacked shape, instead of rounded, building a very striking structure reminiscent of foxtails. This is why it is known in English as “foxtails”.

Depending on the chosen genetics, marijuana flowers can adopt a compact, round and firm structure; or be elongated and narrow. However, what happens with foxtails or phenotrichs is that the calyxes (the space reserved for the seeds to develop) begin to form in groups. This configuration creates a long row of buds, also similar to ears of wheat, which is totally different from the symmetrical nature of most specimens.
While these formations are not harmful, neither are they beneficial, they simply form less compact and bulkier buds.
Factors influencing cannabis foxtails
Usually, the main factor related to foxtails is stress, whereas in some cases it may be due to a genetic mutation. The latter are considered to be positive foxtails, as they tend to have a much higher THC level.
Although, when foxtails occur on account of environmental stress, the consequences for the crop are commonly negative. Some of the factors that affect foxtails are :
Light stress
Cannabis plants need to receive the light needed in order to grow. Nevertheless, if it’s too strong or it’s too close to the flowers, foxtails may appear. A clear evidence for light stress is when leaves start losing their colour and become yellow.

Excessive heat
Excessive heat is detrimental to cannabis plants, which prefer constant temperatures throughout the grow. When temperatures vary too much, they can retard growth and affect yields. In general, there are three different temperature ranges depending on the stage of growth:
- Seedling: 20-25ºC
- Vegetative phase: 22-28ºC
- Flowering: 20-26ºC
If temperatures exceed these ranges for a long period of time, it is possible that they cause foxtails. This excess can be originated by the crop lights, yet also by heat waves.
Root’s zone control
Although you can only observe the plants on the surface, the root zone contains many factors that if left uncontrolled, such as pH, can generate stress in your crop. Cannabis prefers a growing medium that is slightly acidic and between 6.0 and 7.0; these are the values that allow for the best absorption of nutrients.
Harmful microbes
Some species found in the soil form a symbiotic relationship with plants, but others are hostile and can wreak havoc. Particularly relevant among the latter are nematodes, microscopic animals that nibble and devour roots. This type of stress can cause yellowing of the leaves and, in the worst cases, even stunt growth.
How to control or correct cannabis foxtails
Foxtailing, which is produced by external the plant agents, is an indicator that the crop isn’t maturing well. If this occurs at the beginning, i.e. before the buds develop, then the stress should be reduced. In this way, you can try to increase the chances of proper development. Some tips to avoid it from popping up :
- Adjust the lighting frequently. As the plant grows, you will have to raise it, always trying to maintain a distance of about 40 cm in the case of using LED lighting, which are the most recommended as they give off less heat, affecting the temperature fewer. It should be borne in mind that the distance will depend on the type of light used.
- Helping heat dissipation. With the arrival of summer, growing cupboards and greenhouses heat up quickly. To cope with this season’s changes, you can choose to use a digital device to control the temperature. In addition, it is advisable to install several fans for to dissipate the hot air. Another option is to buy a greenhouse with a door or vents. In the case of outdoor growing, it is advisable to use a dark tarpaulin to reduce the heat a little.
- Check the pH with a pH metre once a week to make sure that everything is going well. You can also use different products to raise or lower the pH.
- Microbial balance. In case of nematode invasion, you can add microorganisms for watering. This way you will find different mycorrhizal fungi and rhizobacteria to mix with the pots at the beginning of the cultivation, with the aim of preventing it.
- Give your plants the space they need. They should get their space to develop without disturbing each other, affecting root stress.
When is a plant with phenotrigo harvested?

Once you know what cannabis foxtails are, you need to be aware of the conditions in which these plants develop intending to know how to react if they appear. Thus, when it is not a genetic characteristic, the best thing to do is to keep an eye on the crop so as to correct those factors that may be affecting it negatively.