Marijuana Symptom Overview

Marijuana Symptom Overview – How to identify Common Cannabis Problems

Every grower wants to have healthy, happy plants, but sometimes, Mother Nature has other plans. Catching problems early is always the best way to reduce the damage done by pests, disease, nutrient deficiencies, and environmental stress. This article will give a basic introduction to what symptoms growers should look out for when they check on their plants from i 49 seeds or any other reliable source.

Nutrient Deficiencies

Marijuana plants require sufficient amounts of key macronutrients like nitrogen, phosphorous, and potassium to grow and thrive. They also need trace amounts of other macro- and micronutrients. Here’s how to tell if any of them are deficient.

Nitrogen Deficiency

Nitrogen deficiency causes yellowing of the plants’ lower leaves. The yellowing starts at the tips and moves inward. Stems and petioles also change color, often turning red or purple.

Phosphorous Deficiency

Plants experiencing a phosphorous deficiency develop dark green lower leaves with edges that turn brown or tan. The leaves may also turn blue or purple in spots. New leaves will be small, and the plant will be noticeably stunted.

Potassium Deficiency

Plants lacking in potassium grow tall and leggy, causing their stems to weaken. Their bottom leaves turn brown at the tips and edges and may develop necrosis or chlorosis in spots, but the leaf veins will remain green.

Magnesium Deficiency

The earliest symptoms of a magnesium deficiency are yellowing and weakening of the plant’s lowest leaves. If not caught early, the deficiency will work its way up to the top of the plant.

Calcium Deficiency

The first symptoms of a calcium deficiency are darkening and distortion of new leaves, followed by the development of light brown necrotic spots. The plant will also have weak, hollow stems and branches, discolored shoots, and stunted growth.

Iron Deficiency

The earliest sign of an iron deficiency is chlorosis of young leaves, which then migrates to older leaves. If left untreated, the leaves will yellow and fall off and the plant will be unable to grow and produce buds.

Copper Deficiency

Copper deficiencies also affect new growth first. They cause discoloration of the leaf tips and margins and a yellowing of the flesh between the veins. If this happens to your northern lights strain seeds, the plant’s leaves will wilt and eventually die over time.

Sulfur Deficiency

Cannabis plants with sulfur deficiencies have slim, small, fragile leaves and exhibit slowed growth. The veins may also yellow, especially near the bottom of the leaves. During the flowering stage, the buds will die off.

Boron Deficiency

Boron is not mobile, so deficiencies only affect new growth. Typically plants from auto flowering seeds will have the uppermost leaves will grow slowly and may be deformed, often taking on a brown or gray color before they die. The stems will also hollow out and become rough.

Manganese Deficiency

Manganese deficiencies cause new leaves to turn yellow and develop small brown necrotic spots near their centers. The veins of the leaves stay green, and the outside of the leaves may actually darken, at least at first. Eventually, the necrotic spots will overtake healthy growth and cause the leaf to fragment and disintegrate.

Molybdenum Deficiency

Molybdenum deficiencies are rare. When they occur, they cause plants’ leaves to turn pale and take on a burnt appearance. Right from the beginning, the growth of your bruce banner seeds will appear slow, and older leaves will develop curled tips and rolled margins. The symptoms will start in the middle of the plant, then move upward.

Zinc Deficiency

Zinc causes chlorosis of both old and new leaves and causes the tips of the leaves to die. Affected plants will also experience slowed upward growth, leading to insufficient space between leaf nodes. If it becomes deficient during the flowering stage, the buds will die.

Nutrient Burn

While nutrient deficiencies need to be taken seriously, growers shouldn’t over-apply fertilizers, compost, or plant food. This can lead to nutrient burn. Nutrient burns cause leaves to yellow or develop brown, burnt-looking tips. If left unaddressed, the burn will move inward and kill the leaves and, eventually, the plant.

Plant Diseases

Healthy plants grown from high-quality seeds are less prone to diseases, but few strains are immune to any given disease. Thankfully, the symptoms of plant diseases are usually easy to identify once growers know what to look for.

Algae in Hydroponic Systems

Algae is usually green, but it can also be black, red, or blue. It tends to attach itself to hydroponic equipment and may travel into the tubing. Growers usually see the algae itself but may also notice symptoms of nutrient deficiency in their plants’ leaves and roots. Algae isn’t usually as much of an issue when growing outdoor cannabis seeds, since there should’t be any standing water in contact with the plants.

Bud Rot

Bud rot, also known as gray mold, thrives in cool climates with high humidity. It forms a brown or gray mycelium mass, then infiltrates the stems and buds, which will turn brown and wilt. Never smoke marijuana affected by bud rot.


Damping-off is a reaction to fungal diseases that prevent plants from taking up or properly distributing nutrients. Affected plants develop soft, mushy stems. This eventually causes them to fall over and die.

Fusarium Wilt

Fusarium wilt is a fungal infection that targets marijuana plants’ leaves and roots. It causes wilting and root rot and can be very hard to get rid of. It only affects plants grown in soil.

Leaf Septoria

Leaf septoria is caused by a fungal pathogen most common in warm, humid climates. Also called yellow leaf spot, it affects the lowest leaves of the plant first. Look for circular lesions that vary from white or light brown to yellow.

Powdery Mildew

Powdery mildew looks like a white or gray powder on the plants’ leaves, stems, and buds and it creates a damp, earthy smell. It tends to affect young plants first, and if left unchecked, it causes them to yellow and die. Buying mold resistant strains will absolutely help, but by no means should you expect that they will be completely immune to powdery mildew.

Root Rot

Root rot is caused by the Pythium parasite. It preferentially attacks young, vulnerable plants and plants that are already weakened from other diseases or stresses. The roots of affected plants turn off-color, soft, and watery, and emit an unpleasant smell.

Verticillium Wilt

Plants with verticillium wilt, a fungal infection, show yellowing of the lowest leaves between the veins and outer margins. Eventually, the leaves will turn grayish brown, and the whole plant will wilt and die.

Insects and Pests

Most pests that affect marijuana plants are harmful insects. However, animals can also become a nuisance if they get into outdoor gardens or indoor grow rooms.

Large Numbers of Ants

It’s normal to have a few ants in an outdoor garden. If large numbers of ants colonize the soil surrounding marijuana plants, it can disrupt the roots. Look for earth mounds around the plants and wilting leaves to determine whether the ant population is out of control.

Aphid Infestations

Aphids are tiny green, yellow, black, brown, or red oval-shaped winged insects that hide on the undersides of marijuana leaves. They produce honeydew, which creates a perfect environment for sooty mold. Look for black powder building up on plants and leaves in addition to aphid clusters near the buds.

Corn Borer and Hemp Borer Caterpillars

Corn borer caterpillars bore into the stems of marijuana plants, so they’re difficult to see. Check the plants’ stems for holes with brown trails surrounding them. Look for hemp borers in and around the buds themselves, and look for bite marks on the leaves.

Crickets and Grasshoppers

Crickets and grasshoppers often feed at night, so growers are more likely to notice the damage they cause than the insects themselves. Look for brown patches on the leaves and, in the case of mole crickets, mounds of soil in the garden. These pests are just as hungry for weed seeds as they are the fully grown plant’s stems and leaves, so pay attention through the whole growth process.        .

Cutworm Moths

Cutworms are large, striped or spotted caterpillars that feed on the leaves of young or vulnerable marijuana plants. They’re light-sensitive, so it’s easiest to find them at night. If a plant has bite marks on its leaves, pull up the loose soil around its base and look for small, balled-up caterpillars. They’re usually cutworms.

Deer Problems

Deer are nocturnal and they avoid people, so most growers don’t notice the damage they cause until the next morning. Look for hoof tracks and horrendous amounts of damage, then put up a fence immediately.

Fungus Gnats

Fungus gnats are tiny gray, black, or brown insects that lay eggs near the bottom of marijuana plants. They look like fruit flies, but they’re much more damaging. They consume the root systems of plants, so look for symptoms of root damage such as slowed or abnormal growth and leaf discoloration.

Gophers and Moles

Gophers and moles live primarily underground. They’re known to chew through plants’ root systems while digging their tunnels. Look for fan-shaped gopher mounds with holes on one side and mole paths that look like disturbed soil with cleared areas on either side of the path.


Leaf Miners

Leaf miner larvae burrow between the epidural layers of leaves. They leave squiggly white or brown lines visible from the top of the leaves.

Rats and Mice

Rats and mice are generalized scavengers, so while they prefer other foods, they won’t hesitate to eat marijuana plants if they’re hungry. It’s rare to see the rodents themselves, so look for bite marks on stalks and damaged buds.

Seed-Eating Birds

Birds that eat insects benefit a marijuana garden, but those that eat seeds can decimate a crop. Look for passenger pigeons, mourning doves, bobwhites, pheasants, magpies, starlings, and sparrows hanging around the garden. A hungry bird’s appetite doesn’t distinguish between cheap marijuana seeds and expensive seeds, so make sure you protect your young seedlings from becoming their next salad bar!

Snails and Slugs

Snails and slugs are common pests in marijuana gardens, especially those found in wet climates. They eat both leaves and bugs and can completely decimate small plants. They leave behind a shiny silver trail, kill seedlings, and chew holes in larger leaves.

Spider Mites

Spider mites are tiny, almost microscopic, arachnids that can cause substantial marijuana crop damage. They leave thin white strings between leaves and tiny specks on their flesh from bite marks. Affected plants often look sickly and dirty.


Thrips are small, winged insects that suck the liquid from the insides of marijuana leaves. Affected leaves will develop bronze or silver-colored spots and chlorosis and may eventually turn brittle and die. Thrips also feed on buds.


Whiteflies feed on plants’ leaves and stems, causing leaf chlorosis and death. The easiest way to check for whiteflies is to shake the symptomatic plant. If it has whiteflies, it will look like a cloud of white dust is flying out from underneath the leaves.

Environmental Stresses

Not all plant problems are caused by pests or diseases. A poor growing environment may also be to blame.

Airy Buds

Airy buds are typically caused by poor lighting, excessive heat, poor ventilation, or nutrient deficiencies. They don’t mature properly or get as dense as normal buds, and they contain less THC.

Heat Stress

Heat stress is most common in indoor grows. Look for upper leaves that turn yellow and curl inward. Sativa seeds such as skunk #1 seeds can sometimes tolerate the heat slightly better than indica options like og kush seeds just because their genetic ancestors were developed in hotter regions of the world. This being said, you still need to keep a stable temperature in the acceptable range for your plants to manifest healthy buds.

pH Imbalances

Certain fertilizers, plant foods, and other amendments can alter soil or water pH. Imbalanced pH typically manifests as a nutrient deficiency, so check levels in the soil or nutrient solution before and after every feed to make sure they stay within an optimal range of between 6 and 7.

Soil Problems

Not all soil problems relate to nutrient deficiencies. If the soil doesn’t drain well, it can cause root rot. If it doesn’t retain water and nutrients, plants may wilt and experience stunted growth. It’s always best to start with high-quality loam.

Water Problems

Tap water is usually fine for marijuana plants, but some tap water contains excessive minerals. Signs of hard water include weak-looking, wilted plants, and nutrient deficiencies. If in doubt, filter your water through a carbon block filter or some other accessible means.

Watering Problems

Plants that aren’t getting enough water experience wilting, slowed growth, curled or burnt leaves, and weakened stems. Over-watered plants often develop root rot.

Poor Quality Seeds

Poor quality seeds may not germinate. If growers have had luck germinating plants in the past, but find that they can’t get a particular batch of seeds to grow, it’s time to switch to a new seed bank.

The Bottom Line

Growers who want to produce optimal yields of high-quality marijuana need to be diligent about looking for signs of disease, pests, and environmental stressors. Keep an eye out for the symptoms described above and take action as soon as possible to fix the problem. It’s the best way to avoid crop losses.

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