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Repotting guide

When & how to repot Lemongrass (Cymbopogon citratus)

Also called West Indian lemongrass, sereh, fever grass.

About Lemongrass

Cymbopogon citratus · also called West Indian lemongrass, sereh · herb

Lemongrass is a tropical clumping grass from south Asia with intensely lemon-scented stems and leaves used in Thai and Vietnamese cooking. Tender; grown as an annual or overwintered as a houseplant in cool climates. Toxic to pets due to essential oils.

Lemongrass (Cymbopogon citratus, Poaceae) is a frost-tender clumping tropical grass widely grown in the tropics and subtropics for its lemony stalks used in Southeast Asian cooking; hardy only to about USDA zones 9-10.

Prefers moist loam soil, preferably with high organic content, to fuel its rapid warm-season expansion.

Mature size: 1-1.5 m tall and wide

Watch for — Pot-bound in containers: Divide and pot up annually.

Sources: hort.extension.wisc.edu, plants.ces.ncsu.edu, missouribotanicalgarden.org

How to tell lemongrass needs repotting

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

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 lemongrass

Pot on seedlings as they grow; not a perennial repot. Lemongrassis grown for one season, so the question is really “how often to pot on” — keep moving it up before the roots circle. Clumping tropical grass.

What size pot to step lemongrass up to

Pot lemongrass 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 lemongrass

Pot lemongrass 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 lemongrass

  1. Pot on before it is root-bound. Check lemongrass regularly; move it up as soon as roots reach the edge of the cell or pot, not after they have circled.
  2. 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.
  3. 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.
  4. Pot into rich mix. Set it into fresh rich free-draining loam at the same depth (tomatoes are the exception — they can go deeper to root along the stem).
  5. Water in and grow on. Water well, keep it in good light, and resume feeding once it is established and growing again.

Aftercare

Water lemongrass 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 lemongrass

Lemongrass wants rich free-draining loam. Compost-rich; pH 6.0-7.5. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting lemongrass — frequently asked questions

How often should you repot lemongrass?

Pot on seedlings as they grow; not a perennial repot for lemongrass. Lemongrass is a seasonal crop, so you pot it on as a growing plant rather than repotting a perennial. Step seedlings up gradually into rich free-draining loam 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 lemongrass need?

Pot lemongrass 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. Use our pot size calculator to size it from the plant's current pot and root spread.

When is the best time of year to repot lemongrass?

Pot lemongrass 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.

Can you put lemongrass straight into a much bigger pot?

No. Even a fast-growing lemongrass 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 lemongrass after repotting?

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

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