Sedum, also known as stonecrop, is a popular, well-known perennial garden plant. The succulent leaves, sturdy stems and massive flower heads have earned the plant a spot on many landscapers’ “must have” lists. Besides their physical attributes, sedums are drought tolerant and can withstand many adverse growing conditions, which also makes them ideal landscape perennials. Sedum ‘Black Jack’ is sure to match the tough and easy-to-grow reputation of most sedum cultivars and offers characteristics unparalleled by other sedums.
‘Black Jack’ was discovered by Jerry Van Der Kolk at Walters Gardens Inc., Zeeland, Mich., in a field of sedum ‘Matrona’. This sport of ‘Matrona’ has thick, broad leaves on solid, upright stems and reaches 24 inches in height. In early spring, ‘Black Jack’ emerges with green and light purple foliage that quickly darkens into its characteristic deep purple hue. When grown in full sun the foliage takes on an extremely dark purple-black coloration, the deepest color found in any sedum cultivar. The deep purple foliage provides an excellent backdrop for the bright pink flower clusters that open in late summer.
‘Black Jack’ thrives in sunny locations throughout USDA Hardiness Zones 3-9 and AHS Heat Zones 11-3, although locations receiving partial sun are often acceptable. The characteristic dark purple foliage will take on a lighter coloration when plants are produced at lower light levels. During midsummer, large, broccoli-like flower heads form, containing numerous flower buds. By late summer, the flower buds swell and begin to show a pink coloration. As the buds open, the color intensifies, revealing an impressive color display of bright pink, 8-inch flower clusters.
Sedums are often used as specimen and border plants and in mass plantings. Commercial growers find sedums an easy-to-grow and popular perennial that performs well in containers and is always in demand.
‘Black Jack’ is vegetatively propagated by division. Since a plant patent is being sought (PPAF), unlicensed propagation of this cultivar is prohibited.
‘Black Jack’ is suitable for 1- to 2-gal. containers. Growers usually receive starting materials in the form of bareroot clumps. For the best performance, plant ‘Black Jack’ in a well-drained media, preferably a nursery-type (bark-based) mix rather than traditional greenhouse (peat-vermiculite) media. The porosity (drainage) of the media is not only beneficial during crop production but essential to successfully over-winter sedums, as they do not tolerate wet soils for long durations. When planting bareroot divisions, the crown should be placed in the center of the pot and slightly covered (no more than 1?2 inch) or just exposed after the plants have been thoroughly watered in.
‘Black Jack’ is a light to moderate feeder. Fertility can be delivered using water-soluble or controlled-release fertilizers. Growers using water-soluble fertilizers should either apply 150-200 ppm nitrogen as needed or feed on a constant liquid fertilization program using rates of 75-100 ppm nitrogen with every irrigation. Controlled-release fertilizers are commonly used to produce containerized sedums. Growers commonly apply time-release fertilizers as a top-dress onto the media surface using the medium rate, but they can be incorporated into the growing medium prior to planting at a rate equivalent to 1 lb. of nitrogen per yard of growing medium. The pH of the media should be maintained between 6.0 and 6.5.
‘Black Jack’ requires a below-average amount of irrigation; it is a succulent plant and can tolerate average watering regimes but generally performs best under slightly dry conditions. I recommend, when watering is required, to water thoroughly and allow the substrate to dry between waterings. Keeping ‘Black Jack’ on the dry side will help reduce plant stretch and intensify leaf and stem color.
Height control is often necessary to produce a high-quality product under greenhouse conditions. Providing adequate spacing between the plants will reduce plant stretch. To a certain extent, the height can also be reduced by withholding water and nutrients.
Under certain growing conditions or under high plant densities, it may be necessary to use chemical plant growth regulators. Several of the commercially available PGRs are effective at controlling plant height when they are applied using the appropriate rates, frequency and timing. Depending on your geographic location, apply foliar applications of Sumagic (Valent USA) at 5 ppm or Bonzi (Syngenta Professional Products) at 30 ppm. Two-three applications at 7-day intervals are usually necessary to provide adequate height control. To achieve the greatest results, these applications should begin just as the leaves from adjacent plants are beginning to touch one another.
Sedums are not susceptible to many insect pests or plant diseases. Aphids are the most prevalent insect pest observed feeding on sedums. Crown rot caused by Fusarium or Rhizoctonia is likely to occur when crops are over watered or if the growing medium has insufficient drainage. None of these diseases or insect pests require preventative control strategies. A routine scouting program will detect the presence of diseases or insects early and help growers determine if and when control strategies are necessary.
Sedums can be shipped when green, budded or in full flower. Non-flowering ‘Black Jack’ plants can be sold throughout the growing season from spring to fall due to their purple foliage. Naturally flowering sedums are usually available from late summer to early fall. To improve marketability, ‘Black Jack’ can be forced to bloom throughout the year.
‘Black Jack’ does not have a juvenility requirement and may set flowers with only a few leaves being present. Bareroot materials do not need to be bulked up and can be successfully planted and forced into bloom during the spring. Vernalization is not required to successfully produce flowering ‘Black Jack’ plants.
Sedums are obligate long-day plants and will not flower under short days. As long as the photoperiod is less than 13 hours, sedums will remain as compact, non-flowering rosettes. Growers should provide a minimum of 16-hour photoperiods or 4-hour night interruptions until the flower buds are initiated (after about five weeks) or for the entire forcing duration. Under long-day conditions, or daylengths over 14 hours, flower induction and formation begin. Flower buds may be observed with as little as three weeks of exposure to long photoperiods. Once flower buds are initiated, growers can remove the lighting and finish plants under natural daylengths through the remainder of the forcing. Moving the plants from long days to short days is advantageous to the grower, as it reduces plant height by a couple of inches and reduces the time to flower by 8-10 days. The time to bloom after the proper photoperiod is a function of temperature. ‘Black Jack’ grown at 68° F will take 12-14 weeks to reach flowering, while plants grown at 60° F will flower in approximately 16 weeks.
‘Black Jack’ was discovered and is exclusively available as bareroot plants by Walters Gardens Inc.
This perennial’s dark purple foliage allows for sales even before flowering.