Repotting guide

When & how to repot Lungwort (Pulmonaria officinalis)

Also called Lungwort, Common Lungwort, Jerusalem Cowslip, Spotted Dog.

More about lungwort

About Lungwort

Pulmonaria officinalis · also called Lungwort, Common Lungwort · flowering

Pulmonaria officinalis is a shade-loving, semi-evergreen rhizomatous perennial native to damp woodland and scrub across central and southern Europe. It is valued as an early-spring groundcover, producing clusters of funnel-shaped flowers that open pink and mature to blue-violet, followed by large, white-spotted leaves that remain attractive all summer. The most important care principle is consistent shade and moisture — hot sun and dry soil cause the leaves to scorch and collapse by midsummer. Lungwort contains pyrrolizidine alkaloids and saponins and should be considered toxic to cats and dogs.

Mature size: 25–35 cm tall in flower; clumps spread to 45–60 cm wide over several years.

How to tell lungwort needs repotting

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

Roots spiralling thickly out of the drainage holes or pushing the whole plant up out of the pot.
The pot is so packed that water runs straight through in seconds and barely wets the soil.
It has split a plastic pot, or the rootball is a solid mass with almost no soil left when you slide it out.
Growth and (for lungwort) flowering have clearly stalled despite good light and feeding — but remember this plant likes being snug, so a little crowding alone is not a reason to repot.

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 lungwort

Only every 2–4 years, when genuinely crowded. Lungwort is one of the plants that genuinely prefers a snug pot — it grows and flowers better with its roots a little restricted, so resist the urge to repot it on schedule. Spreading, clump-forming rhizomatous perennial; semi-evergreen, with leaves persisting through mild winters..

What size pot to step lungwort up to

Go up only one pot size — roughly 2–3 cm (about an inch) wider in diameter, no more. Lungwort positively prefers a snug pot: it flowers and grows better when the roots are a little restricted. The single biggest repotting mistake here is over-potting — dropping lungwort into a pot two or three sizes up. All that surplus soil holds water the small root system cannot use, stays cold and wet, and rots the roots within weeks. When in doubt, choose the smaller pot.

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 lungwort

Early spring, just as new growth restarts, is the ideal window for lungwort. The plant is moving into its strongest growth phase and re-roots into fresh soil quickly. Avoid repotting in winter dormancy or, for flowering plants, while it is in bud or bloom — recovery is slowest then and you risk dropping the flowers.

Step-by-step: repotting lungwort

Confirm it actually needs it. Slide lungwort out and check the roots. Only continue if it is genuinely packed — this plant prefers a snug pot, so if there is still soil and room, put it straight back.
Pick a pot only one size up. Choose a pot just 2–3 cm wider with good drainage. Resist anything bigger; over-potting is the main killer here.
Ease it out gently. Water lightly the day before, then tip lungwort out, supporting the base. Tease the outer roots free only enough to stop them circling.
Repot at the same depth. Add a layer of fresh moist, humus-rich, well-drained loam or woodland soil, set the plant so the soil line sits exactly where it did before, and backfill around the sides, firming lightly.
Settle it in. Water once to settle the soil, then let it sit. Hold off on more water until the top of the soil dries — fresh soil around a small root system stays wet for a while.

Aftercare

Because the new soil holds more water than the old crammed rootball did, ease right back on watering — let the top of the soil dry before you water lungwort again, or you will rot the roots in the very pot you just moved it to. Keep it out of harsh direct sun for a fortnight. Do not fertilise for about 4 weeks — fresh mix already carries nutrients and feeding freshly disturbed roots scorches them.

The right soil mix for lungwort

Lungwort wants moist, humus-rich, well-drained loam or woodland soil. Incorporate plenty of leaf mould or well-rotted compost at planting; the roots dislike compacted or waterlogged soil but must never dry out completely. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting lungwort — frequently asked questions

How often should you repot lungwort?

Only every 2–4 years, when genuinely crowded for lungwort. Only repot lungwort every 2–4 years, and only when it is genuinely root-bound — it flowers and grows best slightly crowded. Step up just one pot size in spring using moist, humus-rich, well-drained loam or woodland soil. The key mistake is over-potting: a too-big pot stays wet and rots the roots.

What size pot does lungwort need?

When is the best time of year to repot lungwort?

Does lungwort like to be root-bound?

Yes — lungwort genuinely flowers and grows best when slightly pot-bound, so do not rush to repot it. The mistake to avoid is over-potting into a much larger pot: the excess soil stays wet, the roots cannot use it, and the plant rots. Only repot every few years and only one snug size up.

Should you fertilise lungwort after repotting?

Not immediately. Wait about 4 weeks after repotting lungwort. Fresh mix already contains nutrients, and feeding freshly cut or disturbed roots burns them. Resume your normal feeding routine once you see new growth.