Identify and Solve Hydroponic Plant Problems

This short quiz will help you spot problems with your indoor garden and tell you how to treat them.


1. Your plants’ stems are thin and weak, and the leaves have yellow or white spots. The cause:

a) Lack of nutrients

b) Too much light

c) Insect pests

d) Cold temperatures

Show Solution To Question 1 »

Answer: c. Insect pests—such as whiteflies, aphids, and thrips—suck the moisture and chlorophyll from a plant, leaving stems soft and leaves speckled. These pests even find their way into indoor growing spaces. Solve the problem by spraying a blend of organic pest controls, including neem, pyrethrin, and insecticidal soap.

2. The leaves are firm but curled under and drooping down toward the stem. What’s missing?

a) Oxygen

b) Water

c) Minerals

d) Light

Show Solution To Question 2 »

Answer: a. Plants need oxygen to stay upright and capture light. They get some oxygen from the air but also from water. When the nutrient solution stagnates, the oxygen has been depleted. Replenish the air by gently splashing water in your reservoirs or by pumping it regularly through your system.

3. Your firm, plump, green buds have become soft, crumbly, grayish, and funky-smelling. What’s the problem?

a) Genetics

b) Age

c) Worms

d) Mold

Show Solution To Question 3 »

Answer: d. Botrytis blight, or gray mold, is a very common fungal disease that infects buds just as they are maturing. It thrives in cool, damp conditions, so keeping the grow room’s humidity around 50 percent and the temperature between 65 to 75 degrees Fahrenheit reduces the risk. Immediately remove and dispose of any infected plant, and stop blight from spreading by treating nearby plants with a safe, natural, sulfur-based spray.

4. Your plants grow but not vigorously, and the buds are small and few in number. What do they need?

a) Warmer temperatures

b) Lower pH

c) More fertilizer

d) Brighter light

Show Solution To Question 4 »

Answer: b. In a hydroponic system, the plants need acidic conditions—a pH between 5.5 and 6.5—to take up and use all of the nutrients you provide for them. When the pH is too high or too low, the plants may appear to be deficient of key nutrients, even though you are providing them. Mineral-rich tap water tends to be alkaline (high pH). “Soft” or otherwise treated water may be very acidic. Test the pH of your water before and after you blend in the nutrients. Lower pH with phosphoric or citric acid; raise it with potassium hydroxide or sodium bicarbonate (baking soda).