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Repotting guide

When & how to repot Kale (Brassica oleracea var. sabellica)

Also called curly kale, Tuscan kale, cavolo nero, Lacinato kale.

About Kale

Brassica oleracea var. sabellica · also called curly kale, Tuscan kale · edible

Kale is a cold-hardy leafy brassica that crops from late summer through deep winter and into the following spring. Frost sweetens the leaves. Pair with brassica-friendly companions and protect from cabbage white butterflies. Toxic to pets in large amounts.

Kale is the non-heading (Acephala Group) form of Brassica oleracea, the same species as cabbage and broccoli, derived from wild cabbage of the eastern Mediterranean and Asia Minor and grown as a leafy crop since Greek and Roman times.

Prefers fertile, well-drained soil with a slightly acidic to neutral pH of about 6.0-7.5; like other brassicas it is sensitive to clubroot in acidic, waterlogged ground.

Mature size: 60-90 cm tall

Watch for — Clubroot: Wet acidic soils; lime and rotate, do not plant brassicas in the same spot for 5+ years.

Sources: gardens.duke.edu, plants.ces.ncsu.edu, pmc.ncbi.nlm.nih.gov

How to tell kale needs repotting

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

Pot on seedlings as they grow; not a perennial repot. Kaleis grown for one season, so the question is really “how often to pot on” — keep moving it up before the roots circle. Upright leafy biennial grown as an annual.

What size pot to step kale up to

Pot kale 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 kale

Pot kale 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 kale

  1. Pot on before it is root-bound. Check kale 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, 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 kale 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 kale

Kale wants rich, well-drained loam. Compost-rich; pH 6.5-7.5. Lime acidic soils to deter clubroot. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting kale — frequently asked questions

How often should you repot kale?

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

Pot kale 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 kale?

Pot kale 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 kale straight into a much bigger pot?

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

Not immediately. Wait about 1 week after repotting kale. 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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