Is powdery mildew contagious to other plants?

Yes, the spores travel easily through the air. Keep infected plants away from your other garden favorites.

Should I throw the plant away?

Not necessarily. If you catch it early, pruning and better airflow will usually save the plant.

White horehound: spots, causes and fixes

Check these first

Rub the white spot to see if it wipes off like dust.
Check if the plant is crowded by other vegetation.
Ensure the plant is getting full sun.

Likely causes

Powdery mildew
Most likely
How to tell: The leaves will look like they have been dusted with flour. It usually starts on older leaves and spreads upward.
What to do: Prune away the most heavily affected leaves to improve airflow. Apply a mixture of 1 tablespoon of baking soda in a gallon of water once a week.
Water splashing
Possible
How to tell: Small, irregular spots may appear if soil or hard water splashes onto the leaves. These spots are usually crusty rather than fuzzy.
What to do: Water only at the base of the plant to keep the foliage dry. Mulch around the base to prevent soil from splashing up during rain.

Leaf spots on other plants

Find out what's wrong with your white horehound

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

Powdery mildew is serious if it covers the entire plant and prevents photosynthesis. Small patches are common in humid weather and can be managed with pruning.

Stopping it coming back

Space your plants out to ensure good air movement. Always water at the soil level rather than overhead.

White horehound: spots? Check yours with a photo

Every plant is a little different. Take a photo of your white horehound 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 contagious to other plants?: Yes, the spores travel easily through the air. Keep infected plants away from your other garden favorites.
Should I throw the plant away?: Not necessarily. If you catch it early, pruning and better airflow will usually save the plant.

Guides to these causes

Powdery Mildew

Why does my White horehound have white spots on its leaves?