Is powdery mildew harmful to eat?

It is not toxic, but it ruins the flavor and texture of the fennel. It is best to discard heavily infected parts.

Does this mean my soil is bad?

Not necessarily. Powdery mildew is usually a result of humidity and lack of airflow rather than soil quality.

Florence Fennel: spots, causes and fixes

Check these first

Look for white, dusty patches on the leaves.
Check if the plants are crowded too closely together.
Feel the soil to see if it is staying too wet.

Likely causes

Powdery mildew
Most likely
How to tell: White, dusty spots appear on the leaves and stems, eventually spreading to cover the whole plant. It looks like someone dusted the fennel with flour.
What to do: Remove the most heavily infected leaves to stop the spread. Spray the remaining plant with a mixture of one tablespoon of baking soda in a gallon of water.
Poor air circulation
Possible
How to tell: The plants are crowded together, preventing the leaves from drying out after rain or watering. This creates the perfect environment for fungus.
What to do: Thin out your fennel plants to ensure they have at least 12 inches of space between them. Prune away any foliage that is touching the ground.

Leaf spots on other plants

Find out what's wrong with your florence fennel

The list above covers the usual causes. Pocket Botanist looks at a photo of your actual plant and tells you the likely cause, how serious it is, and what to try first. Identification and a health check are free.

When to worry

It is serious if the spots cover most of the foliage, as this prevents photosynthesis. Minor spots can be managed with pruning.

Stopping it coming back

Water at the base of the plant rather than overhead to keep the leaves dry. Ensure your garden has good airflow by spacing plants properly.

Florence Fennel: spots? Check yours with a photo

Every plant is a little different. Take a photo of your florence fennel and Pocket Botanist tells you which cause is most likely, how serious it is, and what to try first. A few checks a day are free. Save the plant and you get care reminders timed for it.

Get the app · Or check it from a photo now, free

Questions people ask

Is powdery mildew harmful to eat?: It is not toxic, but it ruins the flavor and texture of the fennel. It is best to discard heavily infected parts.
Does this mean my soil is bad?: Not necessarily. Powdery mildew is usually a result of humidity and lack of airflow rather than soil quality.

Guides to these causes

Powdery Mildew

Why does my Florence Fennel have white spots?

Check these first

Not sure what's wrong with your florence fennel?