August 2007 Culture

Verbascum x hybrida ‘Southern Charm’ By Paul Pilon

Through plant selection and breeding efforts, the previous perception of mullein, formerly only recognized as a weed, is gradually changing as gardeners, landscapers and growers are beginning to recognize mullein as desirable ornamental plants. Verbascum x hybrida 'Southern Charm' is the result of such breeding work and offers many improvements over past verbascum species and cultivars. Most notable for growers is the fact that 'Southern Charm' does not require vernalization for flowering and will easily bloom the first year when started from seed.

With its ease of production and first-year flowering, verbascum 'Southern Charm' is a great addition to summer perennial programs. In late spring, 'Southern Charm' produces an abundant supply of uniquely colored flowers consisting of creamy yellow, soft lavender and peachy shades each marked with a fuzzy purple "bee." The blooms are borne on tall, graceful stems that rise from a low-growing rosette of woolly, ovate, silvery-green leaves. The flowering season can be extended by trimming the spent flower spikes, which encourages the plants to re-bloom. After the spring flush of flowers, plants often go dormant during the hot summer months and bloom again in the fall.

In the landscape, verbascum grows best under full sun in locations with dry soils; sites with poor drainage will most likely lead to plant mortality. It reaches 24-30 inches when flowering and spreads 18-24 inches at maturity. It is hardy in USDA Hardiness Zones 5-8 and AHS Heat Zones 9-5. They are generally considered short-lived plants, lasting 2-3 years, especially in hot, humid climates. 'Southern Charm' is ideal as a background plant in flower borders and cutting gardens.

Propagation

Verbascum 'Southern Charm' is propagated from seed. Growers commonly sow 1-2 seeds per cell in 288- to 128-cell plug trays. Cover the seeds lightly with germination mix or medium-grade vermiculite to help keep the seed moist during germination. The seed flats should be moistened and moved to a warm environment where the temperatures can be maintained at 65-68¡ F for germination. To improve germination, many growers use germination chambers to provide uniform temperatures and moisture levels.

It takes 3-7 days for the seeds to germinate. Following germination, reduce the moisture levels somewhat, allowing the growing medium to dry out slightly before watering to help promote rooting. The temperature can also be reduced to 62-67¡ F following germination.

Fertilizers are usually applied once the cotyledons are fully expanded, applying 100- to 150-ppm nitrogen every third irrigation or 75 ppm with every irrigation using a balanced, water-soluble source. When plugs are grown at 65¡ F, they are usually ready for transplanting in 5-7 weeks.

Production

'Southern Charm' is best when produced in large, 1- to 2-gal. containers. They prefer to be grown ? in a well-drained medium with a pH maintained between 5.8 and 6.4. Many commercially available peat- or bark-based growing mixes work well provided there is adequate drainage. Verbascum generally grow best when produced under slightly dry irrigation regimes but also will perform well under more normal watering scenarios. When irrigation is necessary, water them thoroughly then allow the soil to dry moderately between irrigations.

Verbascum is a moderate feeder. Nutrients can be delivered using water-soluble or controlled-release fertilizers. Growers using water-soluble fertilizers apply 75- to 100-ppm nitrogen every irrigation or use 200 ppm as needed. Controlled-release fertilizers are commonly incorporated into the growing medium prior to planting at a rate equivalent to 1-1_ lbs. of elemental nitrogen per yard of growing medium. Growing them under high fertility regimes generally causes them to become very lush and may delay flowering.

'Southern Charm' is a tall plant when produced in containers and marketed in bloom. To maintain plant quality, commercial growers will have to combine both cultural and chemical methods of controlling plant height. The first approach to reducing unnecessary plant stretch during crop production is to provide adequate spacing and withhold water and nutrients (avoid providing luxury amounts). During the rapid elongation of the flower stalks, it may be necessary to apply plant growth regulators. Multiple foliar applications using the tank mix of B-Nine (daminozide) at 2,500 ppm and Sumagic (uniconazole) at 3 ppm will help to reduce elongation.

Insects And Diseases

Although mullein can be produced relatively insect free, aphids, spider mites, thrips and whiteflies often become problematic. These pests can be detected with routine crop monitoring; control strategies may not be necessary unless the scouting activities indicate actions should be taken.

Root and crown rots caused from pathogens such as Phytopthora and Pythium are likely to occur where there is inadequate drainage of the growing medium or when the plants are being overwatered. Although these diseases are less common, it is worthwhile noting that verbascum is also susceptible to downy mildew and Pseudomonas bacterial wilt.

Forcing

Producing flowering verbascum 'Southern Charm' out of season is relatively easy provided a few guidelines are followed. As mentioned, vernalization is not required for flowering, and they will readily flower without receiving a cold treatment. They are obligate long-day plants, absolutely requiring long days for them to flower. To obtain flowering when the photoperiod is naturally short, I recommend providing at least 14-hour photoperiods or night interruption lighting. The time to bloom after the proper photoperiod is provided is a function of temperature. Depending on the size and the age of the starting materials used, it will take 10-12 weeks to reach flowering when they are grown at 67¡ F.

Availability

Verbascum x hybrida 'Southern Charm' is brought to the market by PanAmerican Seed Company. To obtain seed, contact a Ball Seed representative (www.ballseed.com). Plug flats can also be obtained through a Ball Seed representative or various reputable perennial plug producers.