The Complete Guide to Light Bleaching Weed
If you are an expert in growing weed, you probably know how important it is to provide your plants with the right amount and quality of light. However, excessive light can also be detrimental to your plants. One of the possible consequences is light bleaching, a phenomenon that causes the buds to lose their color and potency. In this blog post, we will explain what light bleaching is, what light bleaching weed looks like, and how you can avoid it.
What Is Light Bleaching
Light bleaching (also known as photobleaching) is one symptom of the light stresses that occur when intense light damages photosynthetic pigments like chlorophyll. These pigments are essential for turning light into energy through photosynthesis, helping plants grow and stay healthy. However, too much light damages them, reducing photosynthetic efficiency and ultimately lowering plant quality and yields.
In weed growing, light bleaching refers to the loss of color and quality in flower buds caused by too much light exposure. While it can affect any part of a plant, it’s most noticeable in the buds, which hold most of the aromatic and active compounds. Bleached buds often look white or pale yellow, and usually have lower levels of active compounds along with a weaker aroma and flavor compared to healthy buds.
What Light Bleaching Weed Looks Like
The most obvious sign of light bleaching in plants is when leaves and buds turn white or pale yellow. This usually happens in areas directly exposed to intense light, making them look as if their natural color has been stripped away.
It’s important not to confuse light bleaching with nitrogen deficiency. In cases of nitrogen deficiency, leaves turn yellow and eventually wilt and fall off, starting from the bottom of the plant. By contrast, leaves of light bleached weed typically remain firm and do not fall off, and the discoloration begins at the top, where light intensity is highest.
How to Avoid Light Bleaching Weed
To achieve high quality and a great yield, it is important to avoid light bleaching in weed. Below are some practical tips:
Provide The Right Light Intensity
As a general guideline, aim for a light intensity of about 600–800 micromoles per square meter per second (μmol/m²/s) during the vegetative stage, and around 800–1000 μmol/m²/s during flowering. If you’re supplementing with CO2, plants can handle even more: around 800–1000 μmol/m²/s in veg and 1000–1500 μmol/m²/s in flowering. You can measure this using a PAR meter or a lux meter.
LED grow lights provide a more consistent and controllable light intensity compared to sunlight, and models with dimming functions allow you to fine-tune the light to match each growth stage.
Adjust The Light Distance
A plant’s light needs change throughout its growth stages, so it’s important to adjust the distance between the light and the canopy. A simple hand test can help: place your hand at canopy level, and if it feels too hot or uncomfortable, the light is too close. In that case, raise it to avoid stressing your plants. For precise guidance, check our guide on the light hanging height.
Use Balanced Spectrum
Under a balanced light spectrum, most weed strains can tolerate PPFD levels up to 2,500 μmol/m²/s(with the relative level of CO2) without experiencing light bleaching, which is much higher than the levels where bleaching usually occurs with unbalanced spectra.
Spectra with higher red light content are more likely to cause photobleaching, so the overall intensity needs to be lowered when using them. However, reducing light intensity can lead to lower yields, which no grower wants. This is why using LED grow lights with a balanced spectrum is generally the better option.
Manage Temperature
While high temperatures do not directly cause light bleaching in weed plants, they can exacerbate its effects and put extra stress on the plant. Ideally, keep the temperature in your grow tent between 65°F and 80°F during the day and between 60°F and 70°F at night.
If temperatures climb above these ranges, improve ventilation or add cooling measures such as air conditioning or inline duct fans. Remember that grow lights generate heat, too, so it is a smarter choice to use LED lights with built-in heat sinks.
Introduce Shade
If you’re growing weed outdoors, you can’t control light intensity as precisely as you can with LED grow lights. In this case, you’ll need to take extra steps to protect your plants. For example, you can use shade cloths or move your plants to a shadier spot during the hottest part of the day. It’s also important to consider reducing light exposure time when summer days are especially long in lower latitudes.
Conclusion
Light bleaching is a common challenge that weed growers face when trying to optimize lighting for their plants. By following the prevention strategies mentioned above, you can reduce the risk of photobleaching and support healthier growth and better harvests.
We hope this post has helped you understand what light bleaching is and how to avoid it. If you have any questions or thoughts, feel free to share them in the comments below.
