Pulmonaria

In the past few years, Terra Nova Nurseries has produced a number of new pulmonaria, focusing on garden-worthiness combined with the appeal of improved leaf contrast, superior flower size and colors, and powdery mildew resistance. Patented varieties are virus indexed and produced from tissue culture.

New flower colors, leaf-shapes and dynamite vigor have helped to move pulmonaria up the popularity scale. While there is not enough space to go over each cultivar, here are a few special ones.

'Silver Shimmers' is a low-growing plant with very silver, long leaves and large blue flowers. The undulating edges and patina give this plant the shimmering look for which it is named.

'Emerald Isles' has emerald-green leaves with distinct silver spotting. Tightly clustered pink flowers (which fade randomly to blue) produce an intense floral display.

'Trevi Fountain' has large, silver-spotted leaves with profuse hefty, dark blue flowers.

Tissue Culture

These patented varieties originate in tissue culture planted into 72-cell trays. Plugs are happiest at 65-percent humidity and 65-70° F until halfway rooted. They can then begin cool down to 55-60° F. Pulmonaria need to have cool roots, or they will exhibit heat stress and wilting. During production, keep soil evenly moist; do not allow soil to dry out between waterings. Due to heavy foliage growth and high water usage, this plant is a good candidate for sub-irrigation. Use a balanced fertilizer with micronutrients at 150 ppm constant liquid feed. In the landscape, pulmonaria can tolerate a fairly wide range of pH, but in small plugs iron and sulfur deficiencies can occur above pH 5.8. Plants will not hold in plugs very long before exhibiting stress symptoms like chlorosis and wilting.

Transplanting

Plugs should be transplanted directly into porous soil in 1-gal. pots with a slow-release fertilizer. We recommend a charge of APEX 19-6-12, 6-month microprill formula with minors. Pulmonaria produces thick fleshy roots that quickly outgrow small containers and induce water and nutrient stress. Keep the media moist, but ensure good drainage to avoid root damage. Foliage can wilt at temps above 85° F, but this heat stress should not induce the grower to exercise the common reaction of applying more water. Keep the roots as cool as possible, and foliage will perk up again in the evenings. Keeping plants on the ground will assure the coolest root temps.

Although dormancy is not required for greenhouse production, an 8-week cold vernalization will promote optimum flowering and plant size. Transplanting to 1-gal. pots in late summer (August 21st) or in early fall will allow plants to fully root out before the flowering phase begins in late winter, producing the fullest pot. After flowering is finished, cut back, and the plants will begin to fill out with leaves.

Pests and Diseases

Powdery mildew susceptibility -- once a common problem with pulmonaria -- has been the focus of recent breeding efforts. All of Terra Nova's recently introduced varieties are mildew resistant in the Pacific Northwest.

Botrytis can occur on older leaves at soil level under high humidity conditions. Running a heat/vent dehumidifying cycle, increasing air circulation and applying fungicides such as Heritage as necessary should keep this disease under control. Pulmonaria can produce heavy foliage, inhibiting air circulation around the crown, so thinning may be necessary on older plants.

Aphids are a common occurrence in the greenhouse environment but are easily controlled with scouting and appropriate pesticide usage. Marathon II is used here for control.

It is possible to encounter root rots such as Pythium and Rhizoctonia if the media is not draining well. Addition of perlite or pumice to the mix will ensure better drainage.

If you use hydrogen peroxide products, keep them away from pulmonaria foliage, as they have shown a phytosensitivity, which causes brown spotting of the leaves.