Pulmonaria, commonly called lungwort, is one of the most straightforward shade perennials to propagate by division, and it can also be grown from seed with a bit more patience and unpredictability. Division is the faster and more reliable method, producing exact clones of the parent plant, while seed propagation introduces genetic variation that means your seedlings may not look like their parents. Both approaches work well once you understand the plant’s creeping root system and a few quirks of its reproductive biology.
Why Division Is the More Reliable Method
Pulmonaria spreads by means of a slowly creeping rhizome that sends out adventitious roots along its length.1Journal of Ecology. Biological Flora of the British Isles: Pulmonaria officinalis Over a few years, a single plant forms a spreading clump of rosettes, each with its own root system, that can be separated and replanted. Because each division is genetically identical to the parent, you get the same leaf spotting pattern, flower color, and growth habit. For named cultivars like ‘Diana Clare,’ ‘Majeste,’ or ‘Sissinghurst White,’ division is really the only way to keep the variety true.
Seed propagation, by contrast, shuffles the genetic deck. Pulmonaria species hybridize freely with one another in gardens, and even self-pollinated seed may produce offspring with different leaf markings or flower shades. If you grow a specific cultivar for its silver-spotted foliage, seedlings from that plant can turn out plain green. Division sidesteps all of that uncertainty.
When to Divide
The best window for dividing lungwort is right after flowering finishes, typically from late spring into early summer. The plant is actively growing and has plenty of energy stored in its rhizomes, so divisions establish quickly. Autumn division also works well, especially in mild climates where the soil stays warm enough for roots to settle in before winter. Avoid dividing in midsummer heat, when the plant is already stressed and the foliage is at its most susceptible to powdery mildew.
You can divide a mature clump every three to four years. By that point the center of the clump often starts to look thin or die out, while the outer portions remain vigorous. Division rejuvenates the plant as much as it multiplies it, so even gardeners who don’t need more plants benefit from doing it periodically.
How to Divide Pulmonaria Step by Step
Water the plant thoroughly the day before you plan to divide it. Moist soil makes the rhizomes easier to separate and reduces transplant shock. Then dig up the entire clump with a garden fork, working around the perimeter and lifting from underneath rather than pulling from the top. The root system is relatively shallow, so you don’t need to dig deep, but you do want to get as much of the rhizome network intact as possible.
Once the clump is out of the ground, shake or rinse off excess soil so you can see the individual rosettes and their connecting rhizomes. For most clumps, you can tease sections apart by hand. Each division should have at least two or three rosettes with a healthy cluster of roots attached. If the clump is especially dense or tangled, use a sharp knife to cut through the rhizome cleanly rather than tearing it. A clean cut heals faster and is less prone to rot.
Trim back any damaged or tattered leaves. Some gardeners cut the foliage down to about half its length to reduce water loss while the roots re-establish, though this is optional if the weather is cool and damp. Replant each division at the same depth it was growing before, firming the soil gently around the roots, and water it in well. Spacing of about 30 centimeters apart gives each new plant room to fill out without crowding.
Choosing the Right Spot for Transplants
Pulmonaria thrives in part shade to full shade with moist, humus-rich soil. Dry shade is the one condition where lungwort struggles, so if your soil is sandy or sits beneath thirsty tree roots, work in plenty of compost or leaf mold before planting. A generous mulch of composted bark or leaf litter helps keep moisture consistent and mimics the woodland floor conditions these plants evolved in.
Newly planted divisions are especially vulnerable to drying out during their first few weeks. Keep the soil consistently moist, not waterlogged, until you see new growth emerging. Once established, lungwort is a tough plant that tolerates a fair range of conditions, but it rewards you with better foliage and more flowers when the soil stays evenly damp.
Growing Pulmonaria from Seed
Seed propagation is slower and less predictable than division, but it’s a good option if you want a large number of plants cheaply, or if you enjoy the surprise of seeing what genetic combinations emerge. Lungwort seed is not widely sold commercially, so most gardeners collect their own from existing plants or receive it through seed exchanges.
Pulmonaria seeds ripen in late spring to early summer, roughly four to six weeks after flowering. Each flower produces up to four small, dark nutlets. The seeds are ready to collect when the nutlets darken and separate easily from the calyx. One thing that makes collection tricky is that the seeds don’t ripen all at once on a given stem, and each ripe seed drops quickly. Check your plants every few days during the ripening window. You can also tie a small piece of fine mesh or an old stocking loosely around the flower stems to catch seeds as they fall.
An interesting detail of lungwort seed biology is that each seed carries a small, oily appendage called an elaiosome, which is essentially a food reward designed to attract ants.2PubMed. Tasty rewards for ants: differences in elaiosome and seed metabolite profiles are consistent across species and reflect taxonomic relatedness In the wild, ants carry the seeds back to their nests, eat the elaiosome, and discard the seed underground, effectively planting it. This is why lungwort pops up in unexpected places in gardens. For the propagator, it also means that if you leave ripe seeds on the plant too long, ants may get to them before you do.
Sowing and Germination
Pulmonaria seed germinates best when sown fresh. Viability drops considerably with storage, so if you’ve just collected seed, sow it as soon as possible rather than saving it for the following spring. The simplest approach is to sow fresh seed in pots of moist seed compost in early to midsummer, cover the seed lightly with a thin layer of compost or vermiculite, and place the pots in a shaded cold frame or a sheltered spot outdoors. The seeds need cool, moist conditions and exposure to natural temperature fluctuations to break dormancy.
Germination is erratic. Some seeds come up within a few weeks; others wait until the following spring after experiencing a period of winter cold. This is not a sign of failure. Keeping the pots moist and protected through the winter is key. A covering of grit on the surface helps prevent the compost from crusting over and discourages moss growth during the long wait. If you sow in summer and see nothing by autumn, leave the pots in place through winter and watch for seedlings in the following March or April.
Alternatively, you can sow directly outdoors in a prepared seedbed in a shady spot, scattering seed on the surface and pressing it gently into the soil. This mimics the natural dispersal process and often works well in gardens with reliably moist conditions. Direct-sown seedlings are tougher to monitor and protect from slugs, though, so pot sowing gives you more control.
Why Seedlings Won’t Match the Parent
Pulmonaria is a distylous plant, meaning individual plants produce one of two flower types that differ in the relative lengths of their stamens and styles. This system promotes cross-pollination between the two forms. Research on Pulmonaria officinalis has found that the plant shows weak self-incompatibility, with the two flower forms differing in their rates of seed set after different types of pollination.3Plant Systematics and Evolution. Pollen deposition rates and the functioning of distyly in the perennial Pulmonaria officinalis (Boraginaceae) In practical terms, this means a lungwort plant can set some seed on its own or with pollen from the same flower form, but it sets more seed when cross-pollinated by a plant of the other form.
For gardeners, the consequence is that most seed produced in a mixed planting is the product of cross-pollination, often between different species or cultivars growing nearby. Pulmonaria species hybridize readily, and many garden cultivars are themselves complex hybrids. A seed collected from ‘Mrs. Kittle’ growing near Pulmonaria saccharata might produce a seedling with a completely different leaf pattern and flower color. This is part of the fun for adventurous gardeners, but it means you should never rely on seed propagation to reproduce a named variety.
Studies of pollen flow in Pulmonaria have shown that even the mechanics of pollen transfer between the two flower forms are uneven, with both forms receiving more “wrong-type” pollen than expected based on how much of each pollen type exists.4PubMed. Floral morphology and pollen flow in the heterostylous species Pulmonaria obscura Dumort (Boraginaceae) This complex pollination biology partly explains why seed set in lungwort can be modest and why germination rates are unpredictable. The plants evolved in a system where only a fraction of the available pollen leads to successful seed production.
Potting Up and Growing On Seedlings
Once seedlings have produced their first pair of true leaves, they can be pricked out into individual small pots filled with a general-purpose compost mixed with some perlite for drainage. Handle them by the leaves, not the stem, to avoid crushing the fragile growing point. Keep the pots in shade and water from below by standing them in a tray of water for a few minutes, which encourages roots to grow downward and avoids wetting the leaves excessively.
Seedlings grow slowly in their first year and typically won’t flower until their second spring. Grow them on in their pots through the first summer, potting up to a slightly larger container if roots start emerging from the drainage holes. By autumn, they should be sturdy enough to plant out in their permanent positions. Planting in autumn gives the young roots a full winter and spring to establish before the demands of summer.
You won’t know exactly what your seedlings look like until they flower and develop their mature foliage. Young lungwort leaves are often plain green; the characteristic silver spots and patterns don’t always appear until the second or third season. Resist the temptation to cull seedlings based on unspotted juvenile foliage. Some of the best garden varieties emerged as chance seedlings that looked unremarkable in their first year.
Dealing with Powdery Mildew
The single most common problem with Pulmonaria, whether propagated by division or seed, is powdery mildew. This fungal disease covers the leaves with a white or grayish coating, usually in mid to late summer, and makes the foliage look ragged. It doesn’t kill the plant but it ruins the ornamental effect that you’re growing lungwort for in the first place.
Prevention is more effective than treatment. Consistent soil moisture is the biggest factor: mildew hits hardest when the roots are dry but the air is humid. Mulching, watering during dry spells, and choosing a site that doesn’t bake in afternoon sun all help. Good air circulation matters too, so avoid cramming divisions too tightly together. Some cultivars are notably more resistant than others. Pulmonaria longifolia varieties and hybrids like ‘Diana Clare’ tend to hold up better than some of the older P. officinalis selections.
If mildew strikes badly, the simplest remedy is to cut all the foliage to the ground in late summer. Fresh, clean leaves will grow back within a few weeks, giving you a tidy rosette of foliage for autumn. This is one reason to keep plants well-fed and watered; a well-nourished plant regenerates its leaves much faster after being cut back.
Propagation by Root Cuttings
There is a third propagation method that sits between division and seed: root cuttings. Because Pulmonaria produces adventitious roots along its rhizomes, sections of thick root taken in winter can regenerate into new plants. Cut healthy roots into pieces about five centimeters long, place them horizontally in a tray of moist compost just below the surface, and keep them in a cold frame. Shoots should appear in spring.
Root cuttings are useful when you want to increase a named cultivar but the parent clump is too small to divide without damaging it. The success rate is lower than for division, and some cultivars respond better than others, but it’s worth trying if you have a treasured plant that you’re reluctant to dig up. Like divisions, root cuttings produce genetically identical offspring, preserving the parent’s characteristics.
Ant Dispersal and Self-Sowing in the Garden
Because of the elaiosome attached to each seed, lungwort is classified among myrmecochorous plants, those whose seeds are dispersed by ants.2PubMed. Tasty rewards for ants: differences in elaiosome and seed metabolite profiles are consistent across species and reflect taxonomic relatedness In gardens, this means self-sown seedlings tend to appear in unexpected locations, sometimes meters away from the parent plant, wherever ants have carried and discarded the seeds. Cracks at the base of walls, gaps between paving stones, and the edges of raised beds are common spots where self-sown lungwort turns up.
Whether you encourage or discourage self-sowing depends on how tidy you want the garden to be. In informal woodland plantings, volunteer seedlings can be a bonus, gradually creating a varied groundcover with mixed foliage patterns and flower colors. In more controlled borders, deadheading the flowers before seeds ripen prevents unwanted spread. Since each flower stem produces seed over a period of weeks rather than all at once, you need to deadhead fairly promptly, removing the stems once most of the flowers have faded but before the first nutlets start dropping.
Gardeners who want to control exactly where lungwort grows tend to combine regular deadheading with division every few years, keeping the plants where they want them while preventing the random colonization that ant-dispersed seed encourages. Those who enjoy a more naturalistic approach can simply let the plants do their thing, knowing that any unwanted seedlings pull out easily when small.