Plant Problem Diagnosis Key / Nutrient problems
Nutrient
Potassium deficiency
K
Potassium is mobile and runs the plant's water balance. Shortage shows as scorch along the margins of older leaves and weak stems and fruit.
Signs
- Older leaves yellow at the margins, then turn brown and crisp.
- Blotchy ripening and yellow shoulders in tomato; weak stalks that fall over.
What favors it
Sandy soil, heavy cropping, high calcium or magnesium, and fruiting crops with high demand.
Prevention
- Test the soil and feed potassium to the crop's need.
- Raise potassium during fruiting in fruiting crops.
Often confused with
NutrientFertilizer burn (high salts)
DiseaseVerticillium wilt
Growing conditionsDrought stress (underwatering)
Sources
- Potassium for crop productionUniversity of Minnesota Extension
- Tomato Fruit DisordersUniversity of Missouri IPM
- Potassium and Other Factors Needed for High Quality TomatoesUniversity of Maryland Extension
Treatment by crop
Cultural, biological and chemical options in the order to use them, and notes written for each crop.
Identification is free. Treatment is on the Home and Pro plans.
Questions in the key that lead here
- Look the plant over, leaf undersides included. Are insects, mites, slugs, eggs, webbing or droppings on it?
No, only damage or discoloration - Where is the problem?
Leaves - What does the leaf damage look like?
Color change without distinct spots - Where did the color change start?
Older, lower leaves - What do the older leaves look like?
Yellow then scorched at the edges
Not a match? Start the key or describe what you see.
More photos
More from university Extension: search Extension pages on potassium deficiency, or find a plant diagnostic lab through your state's Extension.