What Your Cannabis Leaves Are Telling You About Plant Health
GROWING

What Your Cannabis Leaves Are Telling You About Plant Health

Yellow tips, white spots, droopy or chewed-up leaves: how to read the warning signs early and get your plants back on track.

BY CosechaLibre Editorial5 MIN READ
Your cannabis plant's leaves are the easiest way to check its health: yellow tips usually point to nutrient burn or heat stress, white spots to mildew, drooping to over- or underwatering, and chewed or damaged leaves to pests. Cannabis is a tough plant, but it still runs into pests and nutrient excesses or deficiencies now and then. These problems show up most often in beginners' grows, but even seasoned growers hit snags with their plants from time to time. The good news: if you catch problems early enough, a few changes to how you grow can put your plants on the road to recovery. One of the simplest ways to spot health issues is to check the leaves every day. The shape and color of a plant say a lot about its health and give you telltale signs of what you're doing wrong or could do better. Here are some of the most common leaf problems.

Yellow cannabis leaves:

When the leaf tips turn yellow, or yellow and slightly curled, it can be a sign of mild nutrient burn from overfeeding. Overdoing the nutrients is a classic rookie mistake from growers who assume more is better. The best move is to read the label and dial the dose back a little. After adjusting, keep a close eye on the new leaves to see whether the problem continues. Yellow leaves can also be a sign of heat stress. Keep your grow space at a steady 23 to 26 °C (73 to 79 °F) to avoid it, and keep the fans running even when the lights are off. pH levels can cause this symptom too.

yellow cannabis leaves

Yellow and brown spots on leaves:

If yellow tips go untreated, the problem gets worse and spreads across most of the leaf. To fix it, get your nutrient dose right. Be careful with growing media that already come loaded with nutrients.

White spots on leaves:

This usually means powdery mildew, a white, flour-like fungus that shows up in grow spaces that are too humid. To prevent it, bring humidity down with better ventilation. To treat it, wipe the leaves with a damp cloth or paper towels and dry them with fans. You can also spray with SM-90, a plant treatment sold in Argentina and Spain (1 part product to 5 parts water), in both veg and flower. During flowering, mold on the buds can look like a fuzzy, cobweb-like ball.

Drooping leaves:

Overwatering and underwatering are two of the most common grower mistakes, especially overwatering. Droopy leaves are a sign of it. Underwatered plants will show weak, limp leaves that end up drooping too. If the soil is dry about an inch (2.5 cm) below the surface, your plants need more water. The fix is easy: get your watering schedule on track and the plants bounce back fast.

Damaged leaves:

When leaves look cut up or damaged, you've got pests. Spider mites are the most common.  These tiny bugs pierce the leaves and suck out the sap. To keep them away, good ventilation is key, along with checking your plants constantly. Spraying them with a miticide a little before lights-out and keeping fans moving air through the grow room can wipe out an infestation. If your grow had spider mites, disinfect the space thoroughly before you start another indoor run. Learning to inspect your cannabis leaves should be a standard part of your growing routine. It lets you treat problems early and save the plant, or at least keep your harvest from tanking.

Yellowing cannabis leaf

How to tell if a cannabis plant is healthy

To judge the health of a cannabis plant, pay attention to several signs, including the color and condition of the leaves. Yellow leaves on a weed plant can point to a bunch of different problems. Possible causes include nutrient deficiencies, over- or underwatering, the wrong soil pH, disease, pests or environmental stress. If your plant's leaves are turning yellow, it may signal a nutrient deficiency, such as nitrogen, iron or magnesium. In that case, you may need to adjust your feeding schedule or use specific supplements to correct it. Droopy leaves can also be a symptom of trouble, like overwatering, poor soil drainage or damaged roots. If that's the case, take a hard look at your watering habits and make sure your growing medium drains well. Beyond yellow and droopy leaves, other things to check when sizing up a cannabis plant's health include its overall growth, spots or discoloration on the leaves, signs of pests or disease, and whether the flowers are developing properly. In short, to figure out how healthy a cannabis plant is, look at several things, starting with the color and condition of the leaves. Yellow and droopy leaves can signal all sorts of problems, from nutrient deficiencies and watering issues to bad pH, disease, pests or environmental stress. The key is finding the root cause and taking the right steps to fix it and get your plant healthy again.

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