October 29, 2019
Growing Woes: Identifying Stress in Your Cannabis Crop
Are your cannabis plants stressed out?
It’s not as easy as just asking your plants how they’re feeling. Well, technically, you can ask them, but chances are you won’t get an answer.
Knowing how your cannabis plants are doing – and noticing if they seem sick or stressed – requires close observation and a keen eye for tell-tale signs and symptoms. Even the most experienced growers can occasionally overlook their crop’s call for help. What can be even more challenging is determining the underlying cause that could lead to sub-par results.
Stress can be a serious concern. It can lead to stunted, wilted plants, or even genetic abnormalities like hermaphroditism, which can easily affect the outcome of an entire crop. If not addressed swiftly and properly, stress can kill a plant. That being said, a little bit of stress can be a good thing: a small amount of UV or infrared light here and there can boost THC percentages and hasten flowering, or many growers use vigorous air circulation to encourage the development of robust plant stalks.
It’s a fine line to walk. Stressing your plants out too much can have dire consequences. Here, we discuss some common symptoms of stressed, unhealthy plants and the potential root of their unhappiness.
A common issue many growers face is yellowing, or even browning, leaf tips. These are usually accompanied by albino buds and leaves that reach up toward the light. The likely cause here? Too much light or heat. Yes, there can be too much of a good thing, and putting your lights too close to the plant canopy – or running them on full-blast for long hours – is a sure-fire way to stress out your crop.
Even though LEDs do run much cooler than their HPS or fluorescent counterparts, you’ll still want to ensure they’re an adequate distance from your plants. Look for light fixtures with excellent uniformity. This can mitigate sections of your canopy getting too much light and other sections withering away in the shadows.
Plants, like humans, need a balanced diet. Growers can support their cannabis plants’ nutrient needs by providing them with a blend of important minerals like nitrogen, phosphorous, potassium, calcium, iron and zinc – just to name a few.
Nutrients are considered either mobile or immobile. The plant may respond with various stress symptoms, depending on the type of nutrient deficiency.
- Mobile nutrients include nitrogen, phosphorous and potassium. Mobile nutrient deficiencies usually are indicated by discolored, curled or drooping leaves near the base of the plant.
- Immobile nutrients include calcium, zinc and manganese. Signs of an immobile nutrient deficiency is often indicated by sickly, spotted or curling newer leaves.
Note that pH issues can easily be misdiagnosed as nutrient deficiencies, so before you get out the fertilizer, check your growing media’s pH. Substrate media should fall between 5.8 and 6.3 and hydroponic solutions should generally fall between 5.5 and 6.5.
This condition can take a toll on a plant seemingly overnight. One day, the plant will be fine, and the next they’ll be yellowing and drooping. Bud rot is mold that is found on the colas, or buds, of the cannabis plant. Keep a close eye on your largest colas – because they’re bigger and denser, they’re more likely to develop bud rot than smaller buds. While bud rot is a serious issue that needs to be quickly caught and dealt with, the good news is that it is easily preventable.
Here’s how to keep mold away from your plants:
- Ensure proper air circulation. Have fans to keep air consistently moving through your grow space. This will prevent microclimates where mold thrives.
- Avoid excessive humidity. Warm, humid air is the perfect environment for mold to grow and for bud rot to take hold. Prevent this through avoiding dramatic swings in temperature, as this can cause condensation. Installing LEDs can help with indoor temperature regulation.
- Consider defoliating. Your biggest, bushiest plants might be pretty to look at, but they could be harboring the perfect microclimate for mold. Give them a prune now and then to keep them in tip-top shape.
Your cannabis plant may begin to develop both male and female characteristics (hermaphroditism). While this can happen in the natural world, it can be disastrous for cannabis growers as it can result in products that are full of seeds. Hermaphroditism is often a plant’s response to stressful conditions, frequently an inconsistent light schedule – especially, interruptions of the dark period during the flowering stage. Even the smallest light leak during a dark photoperiod can cause stress. Make sure your plants are given a completely dark room to rest in and check your lights’ timing schedule ahead of time to prevent mishaps.
Other common factors that can cause hermaphroditism include:
- Incorrect temperature or inconsistencies in temperature
- Damaged roots or over-pruning
- Late harvest
- Overusing pesticides or fungicides
When your plants start showing signs of stress, it can be hard to immediately pinpoint what the issue is. Ask any seasoned cultivator – growing giant cannabis plants, heavy with trichome-laden buds and skyrocketing cannabinoid percentages, takes time, patience and some trial-and-error. We’ve all dealt with stressed out, unhappy plants that sometimes need a little extra TLC to get back on track.
When plants are grown indoors, growers are responsible for maintaining the ideal growing environment across the varying lifecycle of the plant, with the proper amount of light, nutrients, air circulation, temperature and more. So, if you’re just getting started in the cannabis cultivation world (or even if you’ve been at it for a while) make sure you have those environmental controls locked down first. That can prevent many costly and time-consuming issues – like stressed out plants – in the future.