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Fertilising guide

How to fertilise Lungwort (Pulmonaria officinalis)— schedule & NPK

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.

Growth habit: Spreading, clump-forming rhizomatous perennial; semi-evergreen, with leaves persisting through mild winters.

Watch for — 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.

What fertiliser lungwort actually wants — and why

Lungwort is an easy, light foliage feeder — a half-strength balanced liquid feed through the growing months keeps it green without forcing weak, sappy growth.

A balanced general houseplant feed (roughly even N-P-K) is exactly right — it is grown for foliage, so steady, moderate nitrogen for healthy leaves is the goal, not a bloom or root formula.

For the language behind the three numbers on the bottle — what nitrogen, phosphorus and potassium each do — see the NPK ratio explained entry. The short version for lungwort: match the feed to the job the plant is doing right now, not to a generic “plant food” on the shelf.

How often to feed lungwort, and which months

Feeding only earns its keep while the plant is in active growth and can use the nutrients — pour feed into a dormant or low-light plant and it simply builds up as root-burning salt. For lungwort:

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. Treat that as sparingly through the growing season between spring through early autumn (roughly March to September); ease off in autumn and stop entirely in the low light of winter.

The dormant-season rule matters more than the exact interval: skip feeding entirely when lungwort is resting. For the wider context on indoor feeding rhythms across the seasons, the houseplant fertiliser schedule walks through the year month by month.

What strength to mix for lungwort

Half strength is the safe default for lungwort — houseplant feeds are formulated strong, and the diluted dose is gentler on the roots while still ample for foliage.

Feeding always goes onto already-damp soil, never dry roots — water lungwort first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the lungwort watering schedule.

Signs you are over-feeding lungwort

Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for lungwort:

Signs you are under-feeding lungwort

If the symptoms point at watering, light or roots rather than nutrition, the full lungwort care brief covers soil, humidity and the common problems for this species.

Flushing and leaching the salts

Flush the pot of lungwort with plain water until it runs freely from the base every couple of months in the feeding season — it washes out the fertiliser salts that cause brown tips.

Organic vs synthetic feeds for lungwort

Organic options

A diluted seaweed or worm-casting feed, or fish emulsion if you can tolerate the smell indoors. UK: Westland or Baby Bio Organic, dilute seaweed; US: Espoma Indoor! or Neptune's Harvest fish & seaweed. Slow, gentle and hard to overdo.

Synthetic / liquid feeds

A general-purpose houseplant liquid at half strength — UK: Baby Bio, Westland Houseplant Feed or Phostrogen; US: Miracle-Gro Indoor Plant Food or Schultz. Convenient and fast-acting; the only risk is overdoing it.

Brand names are examples, not endorsements, and UK and US ranges differ — check the label’s own NPK and dilution rate, since formulations change.

Fertilising lungwort — frequently asked questions

What fertiliser does lungwort need?

A balanced general houseplant feed (roughly even N-P-K) is exactly right — it is grown for foliage, so steady, moderate nitrogen for healthy leaves is the goal, not a bloom or root formula. Lungwort is an easy, light foliage feeder — a half-strength balanced liquid feed through the growing months keeps it green without forcing weak, sappy growth.

How often should I feed lungwort?

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. 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. Treat that as sparingly through the growing season between spring through early autumn (roughly March to September); ease off in autumn and stop entirely in the low light of winter.

What strength of feed for lungwort?

Half strength is the safe default for lungwort — houseplant feeds are formulated strong, and the diluted dose is gentler on the roots while still ample for foliage.

What does over-feeding lungwort look like?

Brown, crispy leaf tips and edges with no sign of underwatering. A white, crusty salt deposit on the soil surface or pot rim. Weak, pale, stretched new growth that flops. Lower leaves yellow and drop while the soil is correctly watered. Feeding lungwort year-round on a fixed schedule, including dark winter months, is the most common mistake — it cannot use the nutrients in low light and the surplus simply burns the roots and crusts the soil.

Should I flush the soil of lungwort?

Flush the pot of lungwort with plain water until it runs freely from the base every couple of months in the feeding season — it washes out the fertiliser salts that cause brown tips.

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