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Repotting guide

When & how to repot Red Shiso (Perilla frutescens var. crispa 'Atropurpurea')

Also called Purple Perilla, Aka Shiso.

More about red shiso

About Red Shiso

Perilla frutescens var. crispa 'Atropurpurea' · also called Purple Perilla, Aka Shiso · herb

Red Shiso is a deep purple-leaved form of perilla, a mint-family annual key to Japanese cuisine, used to colour pickled plums, flavour dishes, and as a garnish. Its frilled burgundy leaves combine culinary and ornamental appeal. A warm-season herb, it loves sun to part shade, fertile moist soil, and warmth, and self-seeds readily.

Mature size: Around 45-90 cm tall and 30-45 cm wide.

Watch for — Frost death: Any frost kills it outright as a tender annual. Harvest before the first cold snap or grow in pots moved indoors to extend the season.

How to tell red shiso needs repotting

Repotting on a calendar is less reliable than reading the plant. For red shiso, 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 red shiso

Pot on seedlings as they grow; not a perennial repot. Red Shisois grown for one season, so the question is really “how often to pot on” — keep moving it up before the roots circle. Upright, bushy mint-family annual with square stems and frilled purple leaves, branching freely when pinched. Flowers on slender spikes in late summer and self-seeds enthusiastically, often returning year after year..

What size pot to step red shiso up to

Pot red shiso 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 red shiso

Pot red shiso 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 red shiso

  1. Pot on before it is root-bound. Check red shiso 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 fertile, moist, well-drained 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 red shiso 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 red shiso

Red Shiso wants fertile, moist, well-drained loam. Prefers rich, organic, moisture-retentive soil with good drainage at a near-neutral pH around 5.5-7.0. It tolerates average ground but grows lushest and most colourful in fertile soil. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting red shiso — frequently asked questions

How often should you repot red shiso?

Pot on seedlings as they grow; not a perennial repot for red shiso. Red Shiso is a seasonal crop, so you pot it on as a growing plant rather than repotting a perennial. Step seedlings up gradually into fertile, moist, well-drained 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 red shiso need?

Pot red shiso 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 red shiso?

Pot red shiso 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 red shiso straight into a much bigger pot?

No. Even a fast-growing red shiso 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 red shiso after repotting?

Not immediately. Wait about 1 week after repotting red shiso. 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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