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Repotting guide

When & how to repot Skirret (Sium sisarum)

Also called skirret, crummock, sweet water-parsnip.

More about skirret

About Skirret

Sium sisarum · also called skirret, crummock · edible

Skirret (Sium sisarum) is a hardy perennial root vegetable in the carrot family, once a staple before the potato. Each crown produces a cluster of slender, sweet white roots with a flavour between parsnip and sweet potato, best lifted after autumn frosts. It bears umbels of small white flowers and is grown for its tasty, fiddly-to-clean fingered roots.

Mature size: 1-1.5 m tall in flower; roots 15-25 cm long in a clustered crown.

Watch for — Woody root core: Older roots and drought-grown plants develop a tough, stringy central core. Lift first- or second-year roots after frost and keep soil moist for tender flesh.

How to tell skirret needs repotting

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

Pot on seedlings as they grow; not a perennial repot. Skirretis grown for one season, so the question is really “how often to pot on” — keep moving it up before the roots circle. Clump-forming herbaceous perennial with ferny pinnate foliage and tall white flower umbels; forms a crown of multiple slender finger-like roots..

What size pot to step skirret up to

Pot skirret 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 skirret

Pot skirret 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 skirret

  1. Pot on before it is root-bound. Check skirret 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 deep, fertile, moisture-retentive loam, ph 6.0-7.5 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 skirret 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 skirret

Skirret wants deep, fertile, moisture-retentive loam, ph 6.0-7.5. Rich in organic matter and never bone-dry; tolerates heavier, damper soils than most root crops. Deep, stone-free ground lets the roots grow long and straight. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting skirret — frequently asked questions

How often should you repot skirret?

Pot on seedlings as they grow; not a perennial repot for skirret. Skirret is a seasonal crop, so you pot it on as a growing plant rather than repotting a perennial. Step seedlings up gradually into deep, fertile, moisture-retentive loam, ph 6.0-7.5 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 skirret need?

Pot skirret 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 skirret?

Pot skirret 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 skirret straight into a much bigger pot?

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

Not immediately. Wait about 1 week after repotting skirret. 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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