January 2014 Culture

Perennial Solutions: Panicum virgatum ‘Northwind’ By Paul Pilon

Panicum is one of the most widely grown genera of ornamental grasses. In the early 1990s, Roy DiBlik from Northwind Perennial Farm of Wisconsin introduced Panicum virgatum ‘Northwind’. This cultivar was selected as a seedling with a different appearance than the other seedlings from seeds DiBlik had collected in Illinois.

‘Northwind’ differs from most previously introduced cultivars in that it has an upright rather than an arching habit with attractive olive-green foliage. Its beautiful blue-green foliage and dependable upright habit create a stunning vertical accent plant or a dynamic backdrop in landscape beds. In the late summer/early fall, the plant is topped with a multitude of attractive, narrow plumes of open panicles held rigidly and closely above the foliage. As fall progresses, the foliage takes on an attractive golden yellow appearance.

This clump-forming, native ornamental grass tolerates a wide range of soils and growing conditions. Once established in the landscape, ‘Northwind’ is extremely drought tolerant. Upright switch grass is cold hardy and can easily be grown throughout USDA Hardiness Zones 3 to 9. At maturity, this cultivar forms upright clumps reaching 3 to 4 feet wide by 5 to 6 feet tall when blooming. With its attractive foliage and narrow vase-shaped habit, panicum ‘Northwind’ is deer resistant and can be utilized an accent plant or used in background or mass plantings.

Upright switch grass creates a stunning vertical accent and is relatively maintenance and trouble free. Based on its attributes and ease of production, the Perennial Plant Association selected Panicum virgatum ‘Northwind’ as it’s 2014 Perennial Plant of the Year.

Propagation

Panicum ‘Northwind’ is propagated by division. The most successful results are obtained when they are divided in the late winter while the plants are dormant or just as new growth resumes in the early spring. The crowns can be divided or split into smaller sections containing at least one stem, also commonly referred to as a culm or tiller, and several adjoining roots. Panicum can be propagated at other times of the year; however, they do not root as easily as they do just as the plants are waking up from dormancy.

Production

Most growers produce Panicum ‘Northwind’ in 1-gallon or larger containers. They can be planted using rooted liners or bare root starting materials. Use a growing mix which provides good drainage but has a reasonable water-holding capacity; many bark-based growing mixes work well. When transplanting liners, plant them so the soil line of the plug is even with or just slightly below the surface of the growing mix of the container they are going to be grown in. Bare root starting materials should be planted with the crown slightly below the soil surface.

Keep the growing mix of new plantings moist, but not wet, until they become established. Once panicum are fully rooted, they require average to above average amounts of irrigation and can be allowed to dry out more fully between waterings. When irrigation is necessary, water them thoroughly then allow the soil to dry slightly between irrigations.

During production, the pH of the media should be maintained between 6.0 to 6.5. Panicum performs best when they are grown with moderate to high fertility regimes. Growers using water-soluble fertilizers either apply 300-ppm nitrogen as needed or feed with a constant liquid fertilization program using rates of 150-ppm nitrogen with every irrigation. Controlled-release fertilizers can be applied as a top dress onto the media surface using the medium labeled rate, or incorporated into the growing mix prior to planting at a rate equivalent to 1.25 pounds of elemental nitrogen per yard of growing mix.

For the highest quality plants, produce switch grass under high light intensities with a minimum of 5,000 foot-candles. Plants grown under low light levels may appear thin and not be as sturdy as plants grown under ambient conditions.

Due to the growing habit of panicum, it often reaches heights taller than growers would like when producing them in containers. Controlling the height of ornamental grasses is more challenging than most perennials. Foliar applications of plant growth regulators are rather ineffective as the active ingredient of these products does not make direct contact with the elongating stems due to the leaf sheath covering them. Drenching PGRs provides the most reliable height reduction, but still may not provide the amount of height control growers are looking for. For bark-based mixes, 10-ppm flurprimidol, 10-ppm paclobutrazol or 2-ppm uniconazole are good drench rates to begin. Use lower rates in peat-based growing mixes. Drenches should be applied by the time the plants are 6 to 12 inches tall. Later applications seem to be less effective and will not provide the desired results.

Pests and Diseases

Compared to many perennials, the occurrence of insect pests are usually minimal. The primary insect pests of panicum are Japanese beetles, spider mites and thrips. There are several pathogens growers may observe on occasion including Alternaria, Colletotrichum (anthracnose), crown and root rots, Phyllosticta, rust (Puccinia and Uromyces) and Septoria. Most of these pathogens can be reduced by limiting the time free moisture remains on the leaves. Monitor the irrigation practices and the fertility levels on a regular basis, making adjustments accordingly. When these measures are taken, most plant pathogens can be prevented. Control strategies may not be necessary unless the scouting activities indicate actions should be taken.

Temperature and Scheduling

Most growers are interested in producing high-quality, non-flowering plants of panicum. When maintaining 65 to 75º F throughout crop production, 1-gallon pots of non-flowering panicum can be produced from large plugs in seven to nine weeks. Smaller sized liners (72-cell) will take longer to finish. When producing 2-gallon or larger containers, it is usually best to plant them during the summer the year before they are to be marketed.

‘Northwind’ has an obligate cold requirement for flowering. Growers wishing to produce flowering switch grass should provide a minimum of 12 weeks of temperatures less than 40° F. Vernalization can be provided to large plugs or to containerized plants. Panicum are obligate long day plants and will not flower while they are grown under short days. The exact forcing time or weeks to flower has not been determined for ‘Northwind’. If flowering is required, provide at least 14 weeks of long days to vernalized plants at temperatures of at least 68° F.

Availability

Panicum ‘Northwind’ is widely available. Liners can be purchased from Emerald Coast Growers (www.ecgrowers.com), Hoffman Nursery (www.hoffmannursery.com), North Creek Nurseries (www.northcreeknurseries.com), Walters Gardens Inc. (www.waltersgardens.com) and other reputable perennial propagators.