Can I save a bulb that has some rot?

Yes, if the rot is minor, you can cut away the infected tissue and let the bulb air dry for a day before replanting in dry soil.

How often should I water my giant onion?

Water every 7 to 14 days during the active growing season. Keep the soil completely dry while the plant is dormant.

Why is my Allium giganteum bulb rotting? Causes and fixes

Check these first

Check the soil moisture two inches deep with your finger.
Inspect the bulb base for mushy texture or discoloration.
Verify your pot has adequate drainage holes.

Likely causes

Overwatering
Most likely
How to tell: The bulb feels soft or mushy when touched, and the surrounding soil smells sour or swampy. You might see the base of the stem turning dark and slimy.
What to do: Stop watering immediately and allow the soil to dry out completely. If the rot is advanced, dig up the bulb, trim away any mushy parts with a clean knife, and replant in fresh, well draining soil.
Poor Drainage
Most likely
How to tell: Water pools on the surface of the soil for more than a few minutes after watering. The soil feels dense and heavy like clay.
What to do: Amend your soil with perlite or coarse sand to improve aeration. Ensure your pot has large drainage holes at the bottom to let excess water escape.

Root rot in other plants

Find out what's wrong with your giant onion

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

If the entire bulb feels soft or has a strong foul odor, it is likely too late to save. It is normal for the bulb to feel firm and dry during its dormant phase.

Stopping it coming back

Only water when the top two inches of soil are dry and always use a fast draining soil mix.

Giant Onion: root rot? Check yours with a photo

Every plant is a little different. Take a photo of your giant onion 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

Can I save a bulb that has some rot?: Yes, if the rot is minor, you can cut away the infected tissue and let the bulb air dry for a day before replanting in dry soil.
How often should I water my giant onion?: Water every 7 to 14 days during the active growing season. Keep the soil completely dry while the plant is dormant.

Why is my Allium giganteum bulb rotting?