Foxtailing in Cannabis: How to Spot It and What Causes It

Your cannabis plant is foxtailing if, during flowering, its buds grow long, stacked spires of calyxes instead of round, tight nugs, like a fox's tail or an ear of wheat (Argentine growers even call it the "wheat pheno"). It can come from genetics, but it's often a sign of heat or light stress in your grow.

Foxtailing doesn't directly hurt the quality of your weed, but that odd shape can point to several things, from the strain's genetics to stress in the grow.

What is foxtailing in cannabis?

Foxtailing happens when buds grow long and stacked instead of the usual round, compact shape. It usually shows up during flowering and produces buds that look like spikes of wheat, which is why Spanish-speaking growers call it "fenotrigo" (wheat phenotype). In English, it's known as "foxtails" or "foxtailing," because of the resemblance to a fox's tail.

Foxtailing plants aren't harmful, but they're not especially helpful either. They just produce looser, airier, more spread-out buds. Those buds can look impressive, but they don't necessarily change the potency or effects of the weed.

What causes foxtailing on cannabis buds?

Foxtailing can be caused by different factors, from the plant's genetics to stress in the grow. Here are the most common ones behind these formations.

1. Light stress

One of the main triggers for foxtailing is stress from bad lighting. Cannabis plants need the right amount of light to grow properly. If the light is too strong or hung too close to the plants, the flowers can start to foxtail.

On top of foxtailing, light stress can also turn leaves yellow or burn them, which drags down the plant's overall health.

2. Too much heat

Excess heat is another key cause of foxtails. Plants like to grow at stable temperatures, and any big swing can stress them out. During flowering, temperatures above 28 °C (82 °F) can be especially harmful and encourage foxtailing.

Aim to keep these temperatures at each stage of growth:

• Seedling: 20-25 °C (68-77 °F)
• Vegetative stage: 22-28 °C (72-82 °F)
• Flowering stage: 20-26 °C (68-79 °F)

Good ventilation and climate control are key to keeping your plants from heat damage.

3. Keeping the root zone in check

Healthy roots are crucial to how a plant develops, and anything out of whack down there can cause stress and, with it, foxtails. One of the most important things to control is soil pH, which should sit between 6.0 and 7.0 so the plant can take up nutrients properly.

If pH runs too high or too low, the roots can get locked out and the plant will struggle to get the nutrients it needs, which can trigger abnormal growth.

4. Harmful soil organisms

Another thing to watch is what's living in your soil. Some microorganisms help the plant absorb nutrients, but others, like nematodes (tiny root-feeding worms), can do damage. They attack the roots, stressing the plant and, in some cases, encouraging foxtailing.

How to control or fix foxtailing on your plants

Foxtailing can show up on cannabis plants for several reasons, mostly tied to environmental stress. When it does, it's a sign the plants aren't ripening the way they should.

If foxtails show up before the buds have fully developed, it's crucial to find and reduce the source of stress to give the buds a better shot at growing out healthy. Here are some tips for controlling and fixing foxtailing on your plants.

1. Adjust your lighting

The distance between your light and your plants is critical. If you're running LED lighting, keep the fixture about 40 cm (16 in) from the plants.

If you use hotter lamps, like metal halide, you'll need to raise them higher to avoid the light stress that can cause foxtailing.

2. Get rid of excess heat

High temperatures are a major contributor to foxtailing. In summer, grow tents and greenhouses can overheat, which is rough on plants. To keep temperatures in check, consider digital controllers that regulate heat.

Running several fans will also help push hot air out of the space. If you grow outdoors, shade cloth can help bring down the temperature in your growing area.

3. Monitor the pH of your growing medium

Check the pH of your growing medium at least once a week. Keeping it between 6.0 and 7.0 means better nutrient uptake by the roots.

If pH drifts outside that range, use pH up or pH down products to adjust it as needed. Keeping pH in the sweet spot helps reduce stress on your plants and prevent foxtailing.

4. Keep your soil life balanced

Nematodes are among the organisms that can stress roots and contribute to foxtailing. To fight a possible infestation, you can add beneficial microorganisms to your water that take out these parasites.

It's also a good idea to mix mycorrhizal fungi and rhizobacteria into your growing medium at the start of the grow, since they help protect the roots and promote healthy growth.

5. Give them enough room

Plants need enough space, both in the container and above ground, to grow without restrictions. Cramped conditions can cause stress, which in turn can trigger foxtailing. Make sure your plants have plenty of room to develop and avoid overcrowding.

When do you harvest a foxtailing plant?

One of the most common questions from growers dealing with foxtails for the first time is when to harvest. Trichome color is the main sign of when to harvest weed, whether outdoors or in a grow room. When the trichomes turn milky and a few start going amber, it's prime time to harvest.

Keep in mind that bud shape, foxtails or not, doesn't decide harvest time. Foxtailing only affects how the buds look, and once you've fixed the stress problem, let the flowers keep developing normally.

Don't rush to chop your plants just because you're worried about foxtails. Patience is key to a quality harvest.