Whether you have a windowsill full of houseplants or a greenhouse full of tropical beauties, recognizing diseases in plants is essential to prevent greater damage. A sick plant often shows early signs - if you know what to look for. With this checklist, you'll always be one step ahead.
1. Discoloration of leaves
Healthy leaves have a deep, consistent color. Discoloration such as yellow, brown, black or pale green may indicate:
- Nutritional deficiency (often yellow or pale green leaves)
- Too much water (yellow leaves hanging limply)
- Sunlight burn (brown, dry edges)
- Fungi or bacteria (dark spots or patches)
Pay particular attention to sudden changes. One yellowed leaf is not a disaster, but several at once? Then something is going on.
2. Leaf spots, spots and patterns
Irregular dots, circles or spots can indicate fungal diseases such as leaf spot disease, rust or mildew. Do you see a powdery white haze on the leaves? If so, powdery mildew is probably the culprit.
Tip: Use a magnifying glass to see clearly if these are fungal structures, mite damage or insect eggs.
3. Deformed or weak growth
A healthy plant grows vigorously and straight. Do you notice that your plant:
- Remains smaller than normal
- Grows limp and thin
- Draws crookedly or twists
Then there may be root problems, pests, virus infections or too little light. Plants with viruses often grow slowly and show strange leaf structures.
4. Sticky or shiny leaves
Stickiness is usually a sign of insects such as aphids, whiteflies or thrips. These critters excrete honeydew - a sweet substance that leaves a sheen on leaves. Fungi can re-establish themselves on it, such as the sooty mold (black haze on the leaf).
With sticky leaves, always check the underside for small animals.
5. Damage to leaves and stems
See:
- Holes in leaves?
- Eaten edges?
- Jagged leaf structures?
Then you're probably dealing with voracious damage from snails, caterpillars or beetles. In the home, it's often thrips or blowfly larvae that cause damage. Mechanical damage - such as a plant rubbing against something - can also cause discoloration or fraying.
6. Root problems (visible when repotted)
When repotting, you can learn a lot from the roots. Healthy roots are firm, white or light brown, and smell fresh. Black, limp, slimy or smelly roots indicate root rot - usually caused by too much water or poor drainage.
7. Absence of flowering or bud drop
A plant that blooms normally but suddenly stops doing so, or drops flower buds before they open, is having a hard time. Causes may include:
- Temperature fluctuations
- Relocation or stress
- Insufficient light
- Pests or infections
Sometimes this is temporary, but it is a signal that something needs to be adjusted.
Conclusion: every plant tells a story
Diseased plants often give subtle hints before the damage becomes visible. By observing regularly, intervening quickly and getting to know your plants well, you can prevent bigger problems.
Expert tip: Keep a "plant log" in which you record when you water, repot, or notice symptoms. That way you can look back and recognize patterns.
A healthy collection starts with attention - and a little detective work.
