Repotting guide

When & how to repot Citronella Grass (Cymbopogon nardus)

Also called Citronella Grass, Nardus Grass, Sri Lanka Lemongrass.

More about citronella grass

About Citronella Grass

Cymbopogon nardus · also called Citronella Grass, Nardus Grass · herb

Citronella Grass is a large, clump-forming tropical grass native to South and Southeast Asia, grown commercially as the source of true citronella essential oil used in insect repellents and perfumery. It produces tall, graceful, blue-green arching leaves with a strong citrus-like scent when crushed. In temperate climates it is grown as a tender annual or container specimen.

Mature size: 1.5–2 m tall, 1–1.5 m wide (5–6.5 ft tall, 3–5 ft wide)

Watch for — Cold damage / frost kill: Cymbopogon nardus is a true tropical and will be killed to the ground — or to the roots — by frost. In USDA Zones 9 and below, bring container plants indoors before the first frost (typically when nights drop below 10°C). Overwinter in a bright, frost-free greenhouse or sunny room, keeping the soil barely moist.

How to tell citronella grass needs repotting

Repotting on a calendar is less reliable than reading the plant. For citronella grass, watch for these signs:

Roots circling the bottom of the module or pot, or poking out of the drainage holes.
The seedling dries out within a day and growth has visibly stalled.
Roots are white and matted in a tight spiral when you tip the plant out.
It has outgrown its current container for the stage of the season — pot citronella grass on before it becomes hard root-bound.

For the underlying biology of a pot-bound root system and why it stalls a plant, see our guide to spotting and fixing a root-bound plant.

How often to repot citronella grass

Pot on seedlings as they grow; not a perennial repot. Citronella Grassis grown for one season, so the question is really “how often to pot on” — keep moving it up before the roots circle. Large, clump-forming, evergreen tropical grass; produces tall, upright then arching culms from a dense rhizomatous base.

What size pot to step citronella grass up to

Pot citronella grass on gradually — a seedling jumped straight into a huge pot sits in cold, wet, airless soil and stalls. Step up one or two sizes at a time as the roots fill each container, finishing in a large final pot or the ground. The aim is roots that never circle and never check.

Not sure of the exact diameter? Our pot size calculator takes the current pot and root spread and tells you the right next size — it deliberately recommends a single step up, never a big jump.

The best time of year to repot citronella grass

Pot citronella grass on through the active growing season, whenever roots fill the current container — there is no single date, just "before it becomes root-bound". Avoid potting on during a cold snap.

Step-by-step: repotting citronella grass

Pot on before it is root-bound. Check citronella grass regularly; move it up as soon as roots reach the edge of the cell or pot, not after they have circled.
Step up one or two sizes. Choose the next container up — not a giant one. Cold, wet, unused soil around a small root system stalls seedlings.
Knock it out gently. Support the stem, tip the pot, and ease the rootball out without breaking it. A little teasing of circled roots at the base is fine.
Pot into rich mix. Set it into fresh well-drained, moderately fertile loam or loam-sand mix at the same depth (tomatoes are the exception — they can go deeper to root along the stem).
Water in and grow on. Water well, keep it in good light, and resume feeding once it is established and growing again.

Aftercare

Water citronella grass in well and keep it in bright light; a freshly potted-on seedling can wilt for a day while roots settle, so do not overcompensate by drowning it. Do not fertilise for about 1 week — fresh mix already carries nutrients and feeding freshly disturbed roots scorches them.

The right soil mix for citronella grass

Citronella Grass wants well-drained, moderately fertile loam or loam-sand mix. Grows in a broad range of soils (pH 5.5–7.5) provided drainage is adequate. Heavy clay that remains waterlogged causes root rot. Amend poor or clay soils with compost and horticultural grit. In containers, use a quality loam-based compost blended with 20–30% perlite or coarse sand for improved drainage. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting citronella grass — frequently asked questions

How often should you repot citronella grass?

Pot on seedlings as they grow; not a perennial repot for citronella grass. Citronella Grass is a seasonal crop, so you pot it on as a growing plant rather than repotting a perennial. Step seedlings up gradually into well-drained, moderately fertile loam or loam-sand mix so the roots never circle the cell, ending in a large final container. A root-bound transplant stalls and never fully recovers.

What size pot does citronella grass need?

When is the best time of year to repot citronella grass?

Can you put citronella grass straight into a much bigger pot?

No. Even a fast-growing citronella grass should only go up one pot size at a time. A vastly oversized pot holds a reservoir of wet soil the roots cannot reach, which stays cold and soggy and rots the roots — the opposite of what you wanted.

Should you fertilise citronella grass after repotting?

Not immediately. Wait about 1 week after repotting citronella grass. Fresh mix already contains nutrients, and feeding freshly cut or disturbed roots burns them. Resume your normal feeding routine once you see new growth.