Will the leaves grow back?

The plant will grow new leaves from the nodes if the stems are still healthy. Keep caring for it and watch for new green growth.

Is leaf drop a sign of pests?

It can be, but check for rust fungus first. Look for orange spots on the undersides of the leaves that remain on the plant.

Square-stalked St. John's-wort: leaf drop, causes and fixes

Check these first

Check if the soil is bone dry.
Look for signs of rust fungus on the undersides of fallen leaves.
Ensure the plant is not sitting in a drafty area.

Likely causes

Severe drought
Most likely
How to tell: The leaves wilt and then drop off in large numbers. This happens when the soil has been dry for too long.
What to do: Water the plant immediately and thoroughly. Keep the soil damp, checking it every 2 days to ensure it does not dry out again.
Sudden light change
Possible
How to tell: The plant drops leaves shortly after being moved to a new spot. It is struggling to adjust to a different light intensity.
What to do: Move the plant back to its original location if possible. If you must move it, do so gradually over a week to let it acclimate.

Leaf drop in other plants

Find out what's wrong with your square-stalked st. john's-wort

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

Worry if the plant is losing more than a few leaves at once. It is normal for a plant to drop a few leaves when adjusting to a new home.

Stopping it coming back

Keep the plant in a stable location with consistent moisture. Avoid moving it once it is happy.

Square-stalked St. John's-wort: leaf drop? Check yours with a photo

Every plant is a little different. Take a photo of your square-stalked st. john's-wort 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.

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Questions people ask

Will the leaves grow back?: The plant will grow new leaves from the nodes if the stems are still healthy. Keep caring for it and watch for new green growth.
Is leaf drop a sign of pests?: It can be, but check for rust fungus first. Look for orange spots on the undersides of the leaves that remain on the plant.

Guides to these causes

Dehydration

Why is my Hypericum tetrapterum dropping its leaves?