Should I stake my leggy plant?

Staking is a temporary fix, but it does not solve the underlying light issue. It is better to move the plant to a brighter spot.

Will the stems fill back in after I prune them?

Yes, pruning stimulates new growth from the nodes below the cut. This will help your plant look much bushier over time.

Square-stalked St. John's-wort: leggy growth

Check these first

Move the plant closer to a bright window.
Check if the plant is leaning toward the light.
Assess if the stems have been pruned recently.

Likely causes

Insufficient Light
Most likely
How to tell: The stems are long and stretched out with large gaps between the leaves. The plant will lean heavily toward the nearest window.
What to do: Move the plant to a spot with more bright, indirect light. If you are growing it indoors, consider placing it in a south or west facing window.
Lack of Pruning
Possible
How to tell: The plant looks sparse and woody at the base while only growing at the very tips. It has lost its bushy, compact shape over time.
What to do: Prune back the long stems by one third to encourage fuller growth. Do this in early spring to help the plant bush out as it enters the growing season.

Leggy growth 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

It is normal for the plant to grow taller during the active season, but it should not look weak or floppy. If the stems cannot support their own weight, it is time to adjust the light.

Stopping it coming back

Provide consistent bright light and prune the plant annually to maintain a dense shape. This plant does not flower indoors often, but it needs full sun to partial shade to bloom if it does.