With many new selections of pulmonaria available today, lungwort is enjoying a resurgence of popularity. Pulmonaria ‘Polar Splash’ is one of the latest releases to hit the market. ‘Polar Splash’ offers perhaps the most superbly spotted foliage of any pulmonaria currently on the market. Other desirable characteristics of ‘Polar Splash’ include its ability to tolerate more sun than most pulmonaria cultivars and a purpling of the foliage during the winter months.
The foliage forms hosta-like mounds of brilliantly spotted, ovate-shaped leaves that reach 9 inches high by 20 inches wide. It is so impressive that the foliage alone will sell this plant throughout the season, but ‘Polar Splash’ does bear blue to pink flowers in the early spring, which close at night and reopen in the morning. This cultivar is usually utilized as a specimen plant but also works well as a ground cover.
In the landscape pulmonaria performs best in a semi-shady area where it can receive spring sunshine and morning light. It likes average to moist soil conditions and performs well in USDA Hardiness Zones 4-9. Hot afternoon sun and intense heat causes pulmonaria to wilt and the leaves to scorch. It does not perform well in hot, humid climates where it usually goes dormant in the summer and re-flushes in early fall, when the temperature is cooler. ‘Polar Splash’ can tolerate heat and intense sunlight better than most other cultivars, but it will perform best where some shade can be provided.
‘Polar Splash’ is most commonly propagated by tip cuttings. Cuttings can be successfully rooted by sticking them directly into a well-drained growing medium. Many growers dip the unrooted cuttings into a rooting hormone, such as a solution of indolebutyric acid (IBA), at rates between 500 and 1,000 ppm. The rooting compound is not essential for successful rooting, but it tends to provide a slightly higher rooting percentage and also reduces the rooting time. Cuttings should be placed under low misting regimes for approximately the first week of propagation.
Another method of propagation is division, which obviously takes longer and does not produce as many new plants; plants can be successfully divided after they flower in the spring.
When transplanting into the finishing container, plant the ‘Polar Splash’ plug even with the soil line. It performs best in a media with both good water-holding characteristics and adequate aeration. To reduce the likelihood of crown rot and enhance initial rooting, I have found it beneficial to apply a fungicide drench after planting, using a combination of Subdue Maxx (Syngenta) and Cleary’s 3336 (Cleary Chemical).
Maintain media pH throughout the production cycle between 5.6 and 6.5. ‘Polar Splash’ is a light feeder, requiring nitrate levels of 50 ppm under a constant liquid fertilizer program or a controlled-release fertilizer at a rate equivalent to 3?4 lb. of nitrogen incorporated per yard of growing medium.
Keep the growing medium moist; ‘Polar Splash’ requires an average amount of irrigation and does not tolerate overly wet or dry conditions. Prolonged dry periods result in poor foliage quality, necrotic leaf edges and possibly summer dormancy. Leaf scorch is also likely to occur under high light intensities. I recommend producing pulmonaria under 35-percent shade cloth during the summer months.
To produce blooming plants for early spring sales, many growers plant pulmonaria during the late summer and over-winter it in coldframe structures. Pulmonarias do not require cold to flower, but a higher percentage of plants will flower when cold is provided. Pulmonarias bloom so early in the spring that it is often difficult to bulk them up prior to flowering unless they are started during the previous year. Following the cold period, they can be forced under either long or short days, as they are day-neutral plants. When forced under long days the leaves have a more upright leaf orientation, and the blooms are held higher above the foliage.
When plants are bulked during the late summer or early fall, it is important to keep them cool until a few weeks before shipping. Flowering is a function of temperature, if exposed to warm temperatures, you could have flowering plants before there are sales for them. I find it is helpful to provide cooling, holding temperatures less than 50º F during the winter months up to about four weeks before flowering is desired. Depending on geographic location, forcing facility and stage of development of the plant, it is often only necessary to run temperatures of 50-60º F for 3-4 weeks prior to shipping.
It is possible to spring pot a crop of pulmonaria, but it is often more difficult to obtain predictable flowering on full sized plants. For example, the plugs obtained and planted often bloom before they bulk up enough to fill out their container. They will grow and continue to fill out after flowering. I recommend removing the spent flowers to improve the aesthetic appearance and to decrease the time it takes to produce a full pot. When spring potting, it is usually better to use larger starter materials, such as 21-cell plugs, which will most often provide a quicker finishing time. Spring-planted materials are usually grown at warmer temperatures (60-68º F) to promote vegetative growth. ‘Polar Splash’ has great market appeal with or without bloom.
Pests and Diseases
The primary insect pests of ‘Polar Splash’ are aphids and slugs. Generally, I control both of these pests as needed. Routine scouting should be sufficient to determine the presence of both aphids and slugs.
Aphids can be detected on or near fresh new growth. Frequently, when found, they are in surprisingly high quantities, especially if they have gone undetected in previous weeks. There are a number of good insecticides on the market that are both safe and effective at controlling aphids on pulmonaria.
Slugs are often hard to detect, but the plant injury they leave behind will often indicate their presence. Plant injury from slugs appears as irregularly shaped holes with smooth edges. Most often, a slime trail is present on the surface of the leaves near the feeding injury. To control slugs spread a commercial slug bait product such as Deadline (Amvac Chem¬ical) or Sluggo (Western Farm Service) around the production facility.
Powdery mildew is commonly observed on pulmonaria cultivars. At first, powdery mildew appears as small, white, talcum-like colonies on the upper leaf surfaces, but under the right conditions may engulf the plant with a powdery appearance. To control this disease, I have found that it is best to manage the environment by providing the proper plant spacing and adequate air movement and controlling the humidity. However, if desired, you can follow a preventative spray program using the appropriate chemicals. I have observed good results by rotating Compass (Olympic), Heritage (Syngenta), Pipron (SePRO), Systhane (Dow AgroSciences) and Terraguard (Crompton/Uniroyal) as a preventative powdery mildew program.
Pulmonaria ‘Polar Splash’ is a Terra Nova Classic perennial at Terra Nova Nurseries, Tigard, Ore. Unrooted cuttings can be obtained through McGregor Sales and other plant brokers. Rooted liners or finished containers can be obtained from many reputable companies across the country.