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Plant care

Lungwort (Jerusalem Cowslip) care

Pulmonaria officinalis

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

RHS H7USDA 3-8Mildly toxic to petsIndoor 25–35 cm tall in flower

Watering rhythm

Medium indirect light (a couple of metres from a window)

Twice weekly in dry spells; keep soil consistently moist

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Light

Medium indirect light (a couple of metres from a window)

Soil

Moist, humus-rich, well-drained loam or woodland soil

Humidity

Moderate to high ambient humidity; shade-garden conditions

Temp

-25 °C to 20 °C

Pet safety

Mildly toxic to pets

Mature size

25–35 cm tall in flower

Care at a glance

Light

The Goldilocks zone. Not the south-facing windowsill (too hot, too direct), not the back of the room (too dim, growth stalls). Thrives in dappled to deep shade; morning sun is acceptable but afternoon sun causes leaf scorch, particularly in summer when the large leaves are most vulnerable. If you can't decide, a free phone lux-meter app aimed at the leaf at noon should read between 800 and 1,500 lux.

Watering

Watering lungwort: twice weekly in dry spells; keep soil consistently moist. The number that matters isn't the day of the week — it's how dry the top 2-3 cm of the pot feels. A finger in the soil tells you more than a watering app. After every watering, tip the saucer. Drought causes rapid leaf collapse and early dormancy; mulch thickly in spring to retain moisture, especially under trees where root competition is high.

Soil and pot

Lungwort grows best in 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. A pot with a working drainage hole is non-negotiable for this species — even free-draining mix will turn soggy in a closed planter. If you love the look of a decorative pot without a hole, use it as a cachepot around an inner nursery pot you can lift out to water.

Humidity and temperature

Lungwort sits happiest at around Moderate to high ambient humidity; shade-garden conditions humidity and -25 °C to 20 °C (-13 °F to 68 °F). Benefits from the naturally higher humidity found under tree canopies; dry, exposed positions cause rapid leaf curl and poor flowering the following spring. If you keep the room above year-round and avoid placing the plant near a cold draught, a hot radiator, or an air-conditioning vent, you have already handled the two biggest indoor stressors.

Fertilising

Feed lungwort sparingly. Apply a balanced slow-release fertiliser or top-dress with leaf mould in early spring before flowering; avoid high-nitrogen feeds, which produce lush growth susceptible to mildew. Skip fertiliser entirely on a stressed, recently-repotted, or actively wilting plant — fertiliser salts make damage worse, not better. Wait for a round of healthy new growth before resuming a feeding rhythm.

Common problems

Below are the issues we see most often on lungwort in the Growli community. Each is annotated with the most common cause so you know where to start.

  • Powdery mildew — The most common problem: white mealy coating develops on leaf surfaces in warm, dry summers or where air circulation is poor; cut back all foliage to the ground after flowering and the fresh summer flush typically emerges clean.
  • Vine weevil grubs — C-shaped white grubs feeding on rhizomes cause plants to wilt suddenly; apply nematode biological control (Steinernema kraussei) in late summer to early autumn when soil temperature is above 5 °C.

Propagation

Division of rhizomes immediately after flowering in late spring is the standard method; replant sections with at least one strong growth point. Root cuttings taken in autumn also root reliably. Propagation is the cheapest, most satisfying way to expand a collection — and it doubles as insurance against losing a mature plant to an accident. Take a backup cutting once the parent is established and healthy.

Toxicity to pets

Lungwort is mildly toxic to pets. Pulmonaria officinalis is not formally listed in the ASPCA Toxic and Non-Toxic Plant database. However, the plant contains pyrrolizidine alkaloids (hepatotoxic in quantity) and saponins — both classes flagged as harmful to cats and dogs by animal poison control authorities. The coarse trichomes on leaves also cause contact irritation. Classified as mildly-toxic as a precaution; consult a vet if ingestion is suspected. If you keep cats, dogs, or curious children in the house, weigh placement carefully — a high shelf or a hanging planter is enough for casual safety. For severe ingestion incidents, call your local vet and the ASPCA Animal Poison Control Center (in the US, 888-426-4435).

Pet-safety status is sourced from the ASPCA Toxic and Non-Toxic Plant List, which catalogues the most-asked-about plants for cats, dogs, and horses.

Lungwort care — frequently asked questions

What is the common name for Pulmonaria officinalis?

Pulmonaria officinalis is most commonly called Lungwort, but it is also known as Lungwort, Common Lungwort, Jerusalem Cowslip, Spotted Dog. The names refer to the same species, so care instructions for Lungwort apply identically to anything sold as Jerusalem Cowslip.

How much light does lungwort need?

Lungwort grows best in medium indirect light (a couple of metres from a window). Thrives in dappled to deep shade; morning sun is acceptable but afternoon sun causes leaf scorch, particularly in summer when the large leaves are most vulnerable.

How often should I water lungwort?

Water lungwort twice weekly in dry spells; keep soil consistently moist. Drought causes rapid leaf collapse and early dormancy; mulch thickly in spring to retain moisture, especially under trees where root competition is high. The finger-test (or lifting the pot to feel its weight) beats a fixed weekly calendar because pot size, light, and season all change how fast the soil dries.

Is lungwort toxic to cats and dogs?

Lungwort is mildly toxic to pets. Pulmonaria officinalis is not formally listed in the ASPCA Toxic and Non-Toxic Plant database. However, the plant contains pyrrolizidine alkaloids (hepatotoxic in quantity) and saponins — both classes flagged as harmful to cats and dogs by animal poison control authorities. The coarse trichomes on leaves also cause contact irritation. Classified as mildly-toxic as a precaution; consult a vet if ingestion is suspected.

What USDA hardiness zone does lungwort grow in?

Lungwort is rated for USDA zone 3-8 and RHS hardiness H7. Outside that range, grow it as a container plant that overwinters indoors before the first hard frost.

Lungwort deep-dive guides

Every aspect of lungwort care, each with its own calibrated guide:

Featured in these plant shortlists

Lungwort qualifies for 5 curated Growli shortlists — each one filtered objectively from our structured plant-care library, so the selection is consistent and checkable:

Related guides

Lungwort is also known as Lungwort, Common Lungwort, Jerusalem Cowslip, and Spotted Dog.