You’ve set up your grow space like a new parent baby-proofing their home, and begun growing your babies with tender, loving care. You have everything you need to bring them up healthy and strong.

Then, for no apparent reason, things start to go wrong. Your babies begin to wilt, and turn yellow. Male plants keep sending them messages through Facebook, and you find insects with dinner forks lurking at the edges of your grow space. Then a purple elephant walks up to you and says, “Our relationship is over.”

Sitting up in bed with a sheen of sweat on your forehead, you shake the horrible feeling of helplessness and begin to think. You realize you don’t know how to help your plants if they get sick or if things go wrong. Like any parent who loves their children, you want to control the environment and keep them safe.

But what if something does happen? I’m here to let you know that it’s going to be okay. Here is a guide through many of the problems you might face, and how to solve them BEFORE they ruin everything you have worked so hard for.

What Could Possibly Go Wrong?

With cannabis, and any other living thing, there is a delicate balance that needs to be maintained in order to live and thrive.

The main problems that can come up fall into the following categories: Light, water/ soil, and temperature.


light burn How To Grow Marijuana Step 3: Troubleshooting & Solutions
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Plants love light, but you can have too much of a good thing. If your plant is too close to its lights, or the lights are too strong, you can get light burn.

Your plants may show yellow or brown spotting, and the serrated edges of the leaves will curl up. Time to adjust those lights, and increase air circulation to help keep the plants cool.

Water / Soil

If your plant wilts and its leaves start to droop, it could be due to over watering. If it becomes dry and lifeless, it may be under watered. Make sure you wait to water until the soil is dry an inch or more down, and only water until about 20% of the water runs out the bottom.

Ph levels are important. Keeping the Ph of your water stable will help with nutrient absorption, avoiding all kinds of problems.

Root rot can be caused by over watering without proper drainage in soil, but is most often found in hydro systems. Roots will appear slimy and brown, and they will smell. The staining is the nutrients sitting on the roots. Leaves will appear burnt, yellow at the tips, and show signs of various nutrient deficiencies, since the roots aren’t absorbing correctly. The plant will drink less water.

In hydro setups, increase oxygen in the water and use a water treatment, like Hydroguard. What’s dead is dead. Look for new white roots to grow, and new leaves to form. Some hydro water supplements can work in soil as well to treat root rot, look to add them to your water.

Ensure your soil comes from a source free of bugs and contaminants, has no extended release nutrients (like Miracle Gro), and has the right mix of water holding (coco coir) and water draining (perlite) particulates. If your soil has trouble draining, improve drainage with a stick poked into the soil to the bottom of the container, add particulates that will help drain, like perlite. Make sure the drain holes aren’t clogged, and that there is space between them and the tray beneath the container.

If you add nutrients to your water, and store it in your grow area to control temp, good for you. Don’t forget, however, just like that tea mug in your fridge that never gets washed, that standing water is a breeding ground for bacteria and mold. Clean your water containers every couple weeks, and many problems can be avoided.

If your plant is a good size then suddenly stalls in growth, a root bound container might be a problem. Try transplanting to a larger container, and ensure good drainage. See my previous article for transplanting directions, and make sure to loosen the roots.


heatstress How To Grow Marijuana Step 3: Troubleshooting & Solutions
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If you are growing cannabis without a thermostat and a way to regulate temp, you might as well throw the seeds outside and flip a coin. High temps encourage molds, and make nutrient uptake hard, especially the water in hydro systems. Save the hassle and get a thermostat, especially one that reads humidity as well. Moving outside the ideal temp range encourages mold, especially when humidity is higher.

By keeping your floor warm plants can withstand colder air flow better. And in hydro, if you keep your water colder with a chiller, you can keep the room in general warmer, increasing growth.

If your grow room drops below 60 degrees at night, plant growth will slow. If your grow gets above 80 degrees, leaves will curl up, and plants will stretch. Too much heat causes buds to be airy instead of dense.


Okay, first off, I don’t like 99% of the bugs out there! The only good ones are lady bugs, lightning bugs, and roly-polies. Everything else must be killed…with fire! Eww. (Sorry, just writing about them makes my skin crawl.)

There are beneficial bugs, like lady beetles, lacewings, etc. They eat the bad insects that like to eat weed salad like there is no tomorrow. The insects you have to watch out for include:

Spider Mites

spidermite How To Grow Marijuana Step 3: Troubleshooting & Solutions
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Of all the banes of a grower’s life, these buggers are No. 1 on the list. They grow from baby to adult in a week, so they can quickly swell in numbers to ruin a crop. They eat the chlorophyll. Tell tale signs are a thin webbing on leaves and buds, spots on leaves, and the bugs themselves. Ladybugs love to eat them, so buy a bag of them from the garden center, or spray with neem oil and water. When they fall off the plant, their fast metabolism will starve them before they get back up there.

Leaf Miners

leaf miners How To Grow Marijuana Step 3: Troubleshooting & Solutions
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These dirty little suckers look like house flies as adults. They put their young on the underside of leaves where the dig in, leaving white or brown streaks on the tops of leaves. The sprays that will work are bad for the plants, and bad for you. Remove the affected leaves, and kill them old school style if you spot them.

Mealy Bugs

mealy How To Grow Marijuana Step 3: Troubleshooting & Solutions
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Not dangerous unless their numbers swell, obvious signs include white puffy balls, and ants. Deter with lemon juice spray, remove by hand with damp paper towels.

Caterpillars & inchworms

Easy to spot, they eat holes in your leaves and leave piles of brown poop. Some caterpillar types even bore into the plant stalks and eat the plant from the inside out. Watch for holes. Use a bacillus thuringiensis (BT) bacteria spray to stop them being able to eat, and they will die off. Caterpillar BT spray is safe for most good insects, and kills several bad ones, like moths, fungus gnats, and worms. Spray tops and bottoms of leaves weekly right up to harvest.

Fungus gnats

These guys like to start off eating fungus that grows at the base of the plant, the burrow down to destroy roots. Put sticky paper in a ring around your base stem, and you will eliminate most of them. Mix peroxide and water to spray the area to get the rest.


aphid How To Grow Marijuana Step 3: Troubleshooting & Solutions
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Small and hard to spot, these little devils like to drink the plant sap, and can drain the life of your plant’s quickly as their numbers multiply. Use a chopped onion and a couple garlic cloves in a blender, add water to dilute, and spray undersides of leaves and stems.

A great line of products that is both organic and safe for plants, pets, and around children is Spinosad. Great for regular use, and better for you and your medicine.

Other pests can include whiteflies, thrips, crickets, grasshoppers, cutworms, snails, slugs, rats, nice, birds, gophers, and nosy neighbors, and mooching acquaintances.

Most indoor grows that are maintained well won’t have to bother with the likes of deer, but if Bambi starts hanging out next to your “special” shed out back, make sure he can’t get in.


Sooty Mould

Aphids create a sugary waste called honeydew, and deposit it on the underside of leaves and stems. This is where sooty mold grows. The best way to stop this mold is to prevent aphids.

White Powdery Mould

wpm How To Grow Marijuana Step 3: Troubleshooting & Solutions
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If you have patches on your leaves that look like white flour, you have powdery mildew. This can ruin bud. Up to a point, you can fix this. Watch humidity, because excess humidity allows it to live, but more important, increase airflow and fresh air, as this prevents it having the chance to get to your leaves in the first place.

You can clean the white, powdery mildew off plant leaves with a solution of one of the following:

Milk (1:9 ratio of milk to water)

Baking soda (2 tablespoons/ gallon of water)

Neem Oil (4 teaspoons/ gallon of water)

Hydrogen Peroxide (1 teaspoon/ gallon of water of 35% H202)

SM-90 (1:5 ratio of SM-90 to water)

Use paper towels to wipe the leaves clean, and use a different one for each leaf, to prevent cross-contamination. Any buds showing signs or near leaves showing signs, should be trashed, just to be safe.

Bud Rot

root rot How To Grow Marijuana Step 3: Troubleshooting & Solutions
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Bud rot works from the inside out, destroying your buds. It can affect buds when temps cool to 60 degrees, and there is high humidity. It starts off as white fluff, then quickly turns dark brown or black and burrows into the buds.

bud fluff How To Grow Marijuana Step 3: Troubleshooting & Solutions
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All molds need stagnant air and moisture to thrive. Control these and remove any affected parts of the plant carefully, so spores don’t fly everywhere. This mold is toxic. Do not keep buds affected with mold. Defoliating bushy plants can keep moisture from building up on touching leaves and leaves touching buds.


Aside from over watering and bugs, most of the problems you may encounter, especially as a new grower, will be due to nutrient uptake.

At the first sign of nute burn in soil or soil-less grows, flush the grow medium with ph balanced water, no nutrients. In most cases, the plant will bounce back quickly. Make sure you are using the right nutrients for the stage your plants are in. Tomato plant nutes work for cannabis great, but when you can, use nutes specifically designed for pot.

Often, if dosage isn’t the problem, ratio is, and that’s because someone went cheap and didn’t read the label (yeah, guilty, been there).

There are many different nutrients, so check out all the photos below. There is an example of each deficiency. Deficiencies are often caused by your ph swinging outside of the ideal range for cannabis (6.0 – 7.0 for soil) & (5.5 – 6.5 for hydro,soil-less). Some nutes get shut out of roots at the low end of the spectrum, others at the higher end. Nutrient deficiencies can also be signs of a bigger problem.

Just like vitamins help your body in different ways, plant nutrients help plants. We know what vitamins help our eyes, skin, bones, and metabolism. If you care about your plants, it’s a good idea for you to read up on what each one does for them, as well.

boron How To Grow Marijuana Step 3: Troubleshooting & Solutions
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To absorb Boron, your plant needs moisture, Potassium, and Nitrogen. A deficiency shows first as leaves with thick tips, and stems can become rough. Can look like calcium deficient because plants need boron to use calcium. Plants can also show this symptom if phis too high or low.

calcium deficiency How To Grow Marijuana Step 3: Troubleshooting & Solutions
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Hard to identify because it often accompanied other deficiencies. New growth will be curled up, small, distorted. Roots will be underdeveloped or hit by bacteria. Fix with a flush and half strength nutes plus Cal-Mag.

copeer deficiency How To Grow Marijuana Step 3: Troubleshooting & Solutions
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Copper deficiency shows as young leaves are dark and twisted, older growth goes yellow or white. Do a flush and monitor you ph.

manganese deficiecy How To Grow Marijuana Step 3: Troubleshooting & Solutions
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Yellow between the veins with brown splotches, and leaves may fray. Overall growth is stunted. Usually because ph is off or iron is too high. Adjust ph to the lower end of tolerance.

molybdenum How To Grow Marijuana Step 3: Troubleshooting & Solutions
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Starts off with older leaves near the bottom going yellow, but the tell tale sign is a red, orange, or pinkish color appearing on leaves and spreading. Increase ph to higher end of range.

nitrogen deficiency How To Grow Marijuana Step 3: Troubleshooting & Solutions
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Dark green leaves, weak stems, slow growth, clawed tips. The clawed leaves will yellow, while the rest of the plant stays dark green. Nitrogen toxicity in the veg stage will stunt growth. In the end of the flowering stage, leaves will yellow as the plant naturally sucks the nitrogen from them. This is the end of its life cycle, and natural. Do not add more nitrogen, the flowering stage takes far less than the veg, which is why you should have two different formulas.

phosphorous deficiency How To Grow Marijuana Step 3: Troubleshooting & Solutions
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Phosphorus is vital to roots and the flowering stage. Large deficiencies will show gray or purple splotches, minor ones will slow growth overall. It’s hard to give cannabis too much, so if in doubt, add more. Iron and zinc overload can cause phosphorus deficiency.

potassium deficiency How To Grow Marijuana Step 3: Troubleshooting & Solutions
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Won’t absorb if there is too much calcium or nitrogen. Older leaves will curl as the edges yellow, burn, then eventually die.

sulpher deficiency How To Grow Marijuana Step 3: Troubleshooting & Solutions
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All over yellowing, starting with older leaves. Undersides may develop that weird red/orange/pink hue. Discoloration starts at the back of the leaf and works out, unlike other deficiencies. Leaves will become brittle and fall off.

zinc deficiency How To Grow Marijuana Step 3: Troubleshooting & Solutions
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Younger leaves will yellow between veins, giving a unique striped appearance. Vertical growth is halted and new nodes are bunched together.

Again, with deficiencies, do a flush, check ph, temp, and eliminate other possible causes, then resume nutrients at half strength until improvement occurs. Be patient. This can take a few days, or over a week. The parts of the plant that have died stay dead, so watch for improvement on new growth.

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