Discovering a problem with your beloved houseplant can be stressful, but don’t panic! Most common houseplant diseases are treatable with the correct diagnosis and a little care. This library is designed to help you visually identify what’s wrong with your plant and provide you with clear, step-by-step treatment plans. Browse the categories below to find the issue that matches your plant’s symptoms.
What to Do First: A 3-Step Plant Triage
Before diving in, take these immediate steps. This quick checklist can help you narrow down the issue and prevent it from spreading.
- Isolate Your Plant: The moment you suspect a disease, move the plant away from all other houseplants. This quarantine is your single most effective tool against spreading a potential infection.
- Look Closer: Grab your phone’s flashlight or a magnifying glass. Where are the symptoms? On top of the leaves? Underneath? Is it on new growth or old? Note the color (e.g., brown, black, yellow, orange), texture (e.g., dusty, mushy, oily), and pattern of the problem.
- Check for Pests: Many “diseases,” like Sooty Mold, are actually the result of an underlying pest infestation. Look closely at stems, in leaf crevices, and under leaves for tiny insects like aphids, mealybugs, thrips, or scale.
Identify Your Plant’s Disease by Symptom
The easiest way to diagnose a disease is by its most apparent symptoms. Find the category below that best describes what you see on your plant.
Category 1: Problems on Leaves (Spots, Discoloration & Coatings)
This is the most common category, covering anything that appears on the surface of your plant’s foliage.
- Powdery Mildew: You’ll see a distinct white or grayish, dusty coating on the leaves, stems, and sometimes buds. It looks like the plant has been sprinkled with talcum powder. It can cause leaves to yellow and distort over time.
- Fungal Leaf Spot: Characterized by distinct brown or black spots on the leaves. Crucially, these spots often have a well-defined edge and may be surrounded by a yellow “halo.” The spots may be small at first and grow larger or merge.
- Bacterial Leaf Spot: These spots often appear dark, water-soaked, or oily. They may look black and can be angular, limited by the leaf veins. In advanced stages, the spots may ooze a sticky fluid or have a foul smell.
- Rust: This disease presents as small, raised pustules on the undersides of leaves. These pustules are typically orange, reddish-brown, or yellow and contain a powder that can be wiped off, which is the fungal spores.
- Sooty Mold: A black, soot-like coating that can be physically wiped off the leaves. This is not a disease of the plant itself, but a fungus growing on the sugary honeydew excreted by pests like aphids, mealybugs, or scale.
- Downy Mildew: Often confused with Powdery Mildew, but it appears as yellow spots on the top of leaves, with fuzzy grey, white, or purplish mold growing on the underside of the leaves, directly beneath the yellow spots.
- Anthracnose: A destructive fungal disease that causes dark, sunken spots with well-defined edges on leaves, stems, and fruit. The spots can expand rapidly in wet conditions, often forming a “bull’s-eye” pattern.
- Botrytis Blight (Gray Mold): You’ll notice a fuzzy, web-like, grayish-brown mold growing on soft plant tissues like flowers, buds, and dying leaves. It thrives in cool, damp, and stagnant conditions.
Category 2: Problems at the Base & In the Soil (Wilting, Rot & Collapse)
If your plant is collapsing, wilting, or failing from the bottom up, the problem is likely in the soil or at the stem’s base.
- Root Rot: The classic sign is a plant that is wilting dramatically despite the soil being moist. Leaves, often starting with the lowest ones, will turn yellow and drop. If you inspect the roots, they will be brown, mushy, and easily pull apart, and the soil may have a foul, rotten smell.
- Stem and Crown Rot: The base of the plant, right at the soil line (the crown), becomes soft, brown or black, and mushy. The plant may fall over, or the main stem may feel squishy. This is a severe condition that can quickly kill a plant.
- Damping Off: A frustrating problem that specifically targets seedlings or fresh cuttings. The young plants will appear healthy one day and suddenly collapse the next, with the stem shriveling and rotting right at the soil line.
Category 3: Systemic & Viral Issues (Unusual Patterns & Decline)
These issues affect the entire plant system and often present as strange patterns rather than distinct spots. They are less common in houseplants but critical to identify.
- Dasheen Mosaic Virus (DsMV): This viral disease is a significant concern for Aroid collectors. It presents as unusual feathered yellow patterns, mosaic-like patches, or light-colored mottling on the leaves that often follow the veins. It does not kill the plant, but it affects its appearance and can spread.
- Other Mosaic Viruses: A general category for viral infections that cause symptoms like mosaic or mottled light and dark green patterns, yellow ring spots, or distorted leaf growth. Viral diseases cannot be cured.
The Best Defense: How to Prevent Houseplant Diseases
The most effective way to treat a disease is to prevent it from ever occurring. Healthy, unstressed plants are much better at resisting pathogens.
- Provide Good Airflow: Stagnant air is a breeding ground for fungal spores. A gentle fan or simply not crowding your plants too closely can make a huge difference.
- Water Correctly: The #1 rule. Always check the soil moisture before watering to ensure optimal watering. Most houseplants prefer to dry out partially between waterings. More plants are killed by overwatering than by underwatering.
- Use Appropriate Soil: Use a fresh, chunky, well-aerating soil mix suitable for your plant. Dense, heavy soil holds too much water and suffocates roots.
- Quarantine New Plants: Keep any new plant you bring home separate from your collection for at least 2-4 weeks. This gives you time to observe it for any hidden pests or diseases.
- Sterilize Your Tools & Pots: Always clean your pruning shears, trowels, and pots with rubbing alcohol or a bleach solution between plants to avoid cross-contamination.
- Inspect Regularly: Make it a habit to look over your plants once a week. Catching a problem when it’s just one spot on one leaf is far easier than when it has spread to the entire plant.
Still can’t identify your plant’s problem? Join our community forum to post pictures and get advice from fellow plant lovers, or check out our guide to common houseplant pests to see if an insect might be the culprit.
