(Editor's Note: This article was originally published on August 22, 2009. Your comments are welcome, but please be aware that authors of previously published articles may not be able to promptly respond to new questions or comments.)
One of the most recognizable garden perennials are the lungwort, from the genus Pulmonaria (Boraginaceae). An overview of this genus was provided in an earlier article by Jeannette Adams (adamsbydezign). This article will look at Pulmonaria from a more botanical angle and introduce you to some of the noteworthy selections.
Lungwort have had a long history as a garden plant. They were cultivated since the 16th century in Europe and were among the earliest European flowers to be cultivated in the Americas, known to be in the botanical garden started by John Bartram in 1728 near Philadelphia. This hardy plant (zone 3) is still a garden stable today with new cultivars arising yearly. They have a wide variety of uses in the garden, from partly shaded mixed borders, woodland gardens, groundcovers, rock gardens, edges of water gardens, containers and wildlife gardens (they are very attractive to bees).
Most gardeners know that many lungwort blossoms change from pink top blue as the flowers age. This feature is actually common throughout the Borage Family. This change in floral colour is thought to be a signal for pollinating insects to let them know if the flower is too young to provide pollen and nectar, too old (ie. they have already been visited and pollinated) or just right. Bees, the primary pollinators of lungwort, see very well into the ultraviolet and in that range of light, the pink to purple to blue colour change of lungwort flowers is even more dramatic. The uniqueness of lungwort flowers doesn't end there; their flowers are heterostylous. That means that an individual plant either has stamens that are longer than the style (termed thrum flowers) or styles that exceed the length of the stamens (termed pin). This feature is also found in many primroses. This characteristic ensures cross-pollination as pin flowers will not pollinate another pin and likewise for two thrum flowers. To get seed, you must cross a pin to a thrum or vice versa. This is important to know if you ever wish to do some experimental hybridizing within Pulmonaria! From a gardeners perspective, you might be interested to know that pin-flowered plants usually have larger flowers.
If you look carefully, you will see the exposed style of the pin flower on the left and the lack of an exposed style, but exposure of the stamens on the thrum flower to the right
There are nearly a hundred cultivars of lungwort on the market. Most of these selections are derived primarily from three species: P. saccarata, P. officinalis and P. longifolia. Perhaps the most sought-after cultivars are those with completely silver leaves. ‘Majeste' is among the most famous of these but other equally attractive silver to mostly sliver-leaved cultivars are ‘Cotton Cool', ‘Diana Clare', ‘Pewter', ‘Excalibur', ‘Margery Fish', ‘Samurai', ‘Silver Shimmers' and ‘Spilled Milk'.
Examples of silver-leaved lungwort are 'Majeste', 'Diana Clare' (top rows), 'Cotton Cool' and 'Samurai' (lower row)
If you prefer white flowers, then grow ‘Sissinghurst White', ‘Glacier', ‘White Wings', ‘Ice Ballet' or ‘Opal' (really a very pale blue). ‘Roy Davidson' has flowers that open and remain blue while the flowers of ‘Dora Bielefeld' open and remain coral-pink. Even more dramatic is the new cultivar ‘Raspberry Splash' whose flowers are deep raspberry-pink.
Details of 'Sissinghurst White' (left and middle) and 'Opal' (right)
Details of 'Dora Bielefeld', 'Roy davidson' and 'Raspberry Splash'
If space is limited try ‘Baby Blue', a dwarf selection (20 cm) whose flowers change from light pink to pale blue. ‘Purple Haze' is another compact selection with a profusion of violet-blue flowers. Perhaps the most striking of the dwarf selections is P. longifolia ssp. cevennensis. This one has distinctly long, narrow leaves and are very densely spotted and streaked in silver.
Details of 'Baby Blue' and P. longifolia ssp. cevennensis
There are two additional species that often appear in gardens. Both of these have unspotted foliage. Pulmonaria angustifolia is a deciduous species (the previous cultivars noted are semi-evergreen) that forms clumps of dark green leaves and bright blue flowers that open from pinkish buds. The true species is probably quite rare in gardens but there are a number of selections that are often seen. The differences between these are subtle. The most common selection is ‘Azurea', but others you may encounter include 'Blue Ensign', ‘Munstead Blue', ‘Blue Pearl' and ‘Mawson's Blue'.
Deatils of P. angustifolia 'Azurea' and 'Blue Ensign'
Pulmonaria rubra, the other plain-green species, is often the first lungwort to bloom, often within days of the melting snow. At this stage, the flower stems are quite short. As the season progresses, the later flower stems may exceed 50 cm. In my garden, this species has the longest blooming period of any lungwort. The semi-evergreen foliage is usually brighter green than the other lungwort. Flowers open and remain coral to reddish-pink. ‘Redstart' is among the most popular of the selections but others include ‘Barfield Pink', ‘Barfield Ruby' and ‘Bowle's Red'. The cultivar ‘David Ward' has leaves that are attractively edged in white. ‘Berries and Cream' is a ‘Redstart' X ‘Excalibur' cross which has the silvery foliage of the latter selection and the reddish-pink flowers of ‘Redstart'.
Details of P. rubra 'Redstart'
These are but a few of the attractive lungworts that exist. New selections arise every few years. All make admirable plants for a variety of garden situations combining beautifully with Hosta, ferns, Heuchera, Hellebores and other woodlanders.
I would like to thank the following people for the use of their pictures: altagardener ('Samurai'), angihansen ('Diana Clare'), Carkeekfish ('Roy Davidson'), chicochi3 ('Baby Blue'), Galanthophile ('Cotton Cool' and 'Blue Ensign'), growin (P. longifolia ssp. cevennensis), jody ('Raspberry Splash'), Meighan (thrum flowers) and RoyB ('Opal')