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Repotting guide

When & how to repot Korean Mint (Agastache rugosa)

Also called Korean mint, blue licorice, wrinkled giant hyssop.

More about korean mint

About Korean Mint

Agastache rugosa · also called Korean mint, blue licorice · herb

Korean mint is an upright, aromatic perennial in the mint family with anise-licorice-scented leaves and tall spikes of purple-blue flowers that draw bees and butterflies. Used as a culinary and medicinal herb across East Asia, it thrives in full sun and well-drained soil, is fairly drought-tolerant once established, and self-seeds readily in the garden.

Mature size: 0.6-1.2 m tall and 0.3-0.5 m wide, forming an erect, bushy clump.

Watch for — Winter wet rot: Cold, soggy soil kills the crown over winter more often than cold itself; ensure sharp drainage or grow in raised beds and pots.

How to tell korean mint needs repotting

Repotting on a calendar is less reliable than reading the plant. For korean mint, 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 korean mint

Pot on seedlings as they grow; not a perennial repot. Korean Mintis grown for one season, so the question is really “how often to pot on” — keep moving it up before the roots circle. Upright, clump-forming aromatic perennial that flowers from mid to late summer; self-seeds freely and can be short-lived, persisting via seedlings..

What size pot to step korean mint up to

Pot korean mint 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 korean mint

Pot korean mint 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 korean mint

  1. Pot on before it is root-bound. Check korean mint 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 average, well-drained soil 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 korean mint 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 korean mint

Korean Mint wants average, well-drained soil. Best in fertile, free-draining loam with a neutral pH; tolerates poorer ground. Sharp winter drainage is important, as wet, cold soil is the main cause of plant loss. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting korean mint — frequently asked questions

How often should you repot korean mint?

Pot on seedlings as they grow; not a perennial repot for korean mint. Korean Mint is a seasonal crop, so you pot it on as a growing plant rather than repotting a perennial. Step seedlings up gradually into average, well-drained soil 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 korean mint need?

Pot korean mint 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 korean mint?

Pot korean mint 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 korean mint straight into a much bigger pot?

No. Even a fast-growing korean mint 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 korean mint after repotting?

Not immediately. Wait about 1 week after repotting korean mint. 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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