Leaves play vital roles in cannabis plant physiology. First, they serve as biological solar panels. The pigment that gives them a vibrant green appearance, chlorophyll, works to absorb sunlight that plants then convert into energy. Cannabis leaves also feature many tiny pores (stomata) that open and close on demand to allow water and oxygen to escape and carbon dioxide to enter.
Cannabis leaves are extremely important to plants, but they serve an additional purpose for growers. The symptoms of many deficiencies, infestations, and diseases manifest in the leaves, which means cultivators with a keen eye can use these signals to act fast and bring their plants back to good health. These vegetative surfaces serve as a one-way communication interface between grower and plant, but only if you know what to look for.
Discover five of the most common cannabis leaf symptoms below, their causes, and what to do if they rear their heads, according to our expert source.
Walking into your grow room or garden and spotting wilting leaves can really take the wind out of your sails. Although it looks severe, growers can usually take swift steps to remedy the underlying issues. Check out some main causes behind this symptom, and how to fix them.
Plants need water to photosynthesize, transport nutrients, and remain turgid and strong. Without it, they’ll soon look a little worse for wear. Luckily, underwatering is the easiest because of wilted leaves to fix. Simply give your plants a drink. As a rule of thumb, you should water them as soon as the top couple inches of soil dry out.
You read that right. Prolonged exposure to wind can burn foliage and cause it to wilt. If you’re growing outdoors, move your potted plants, or set up a temporary windbreak around those growing directly out of the ground.
Disease-causing fungal organisms, such as Verticillium species, attack the roots of cannabis plants, resulting in wilting. To combat this pathogen, remove and destroy infected plants, and move healthy plants to a new area. Consider treating your soil with beneficial microorganisms, such as rhizobacteria and mycorrhizal fungi, to prevent the bad guys from getting a foothold in the soil.
Yellow leaves look even more threatening than wilting ones. Unfortunately, various causes underpin this sickly look. Still, there are various measures you can take to remedy the situation.
Are you overfeeding your plants? Excess nutrients won’t help them prosper. In fact, it can cause myriad issues and result in a sick and yellow appearance. If you’ve overdone it, start by flushing your plants. Give them nothing but water for the next week. When the symptoms start to subside, dial back on nutrients and work your way up to the amount recommended for your chosen product.
Too little water causes wilting, but too many causes yellowing. Excess water also suffocates roots (they need air, too) and serves as a breeding ground for detrimental anaerobic bacteria. The fix? Simply stop watering your plants until the top few inches of soil become dry. Stick to this measure before watering in the future.
Just as too much feed can cause yellowing, so can too little. Your cannabis plants require an array of macronutrients and trace minerals to thrive. To counter yellowing, start out with a generous foliar feed of liquid seaweed. It contains many key nutrients, and plants absorb nutrients the fastest through their leaves. Going forward, stick to a strict feeding regimen.
Crispy leaves make weed plants look like they’re on their last legs. Although they’re certainly heading in that direction, there are a couple of things you can do to turn the situation around.
Sometimes, cannabis plants simply get too hot. Whether you’ve positioned your lights too close to the canopy or you’re enduring a freakish heatwave outdoors, your plants can only take so much. Excess heat can dry out the tips of leaves—especially those near the top of the plant—and cause them to become crispy.
Indoors, you’ll need to position your light higher to protect the canopy from the heat emitted. Outdoors, erect some shade cloth during the worst of the weather to shield your plants against the heat of the day.
A whole host of wriggling, crawling, and flying creatures will take chomps out of your cannabis leaves if given the chance. Below, you’ll become acquainted with two of the major culprits.
Caterpillars appreciate the succulent taste of many green, leafy vegetables, and cannabis is no exception. These wrigglers can quickly strip leaves bare, so you need to act fast. Start off by removing all visible caterpillars by hand. If you’re dealing with a big crop and a sizeable infestation, apply the bacteria Bacillus thuringiensis to beat back these grazing insects.
Thrips are another common leaf-chomping pest. Thrip damage manifests as irregular white marks that can drastically reduce the aesthetics of an otherwise smooth and waxy fan leaf. The answer? Create a formula using neem oil or insecticidal soap to quickly purge them from your plants.
Honeydew might sound pleasant, but it’s anything but. These translucent drops of fluid are secreted by aphids after they feed on cannabis sap. These critters are one of the most common cannabis pests out there, and they can cause real damage to leaves if left unchecked. To deal with aphids, douse them with insecticidal soap. Following that, introduce ladybugs into your garden to manage their levels in the future.