The pink-flowered ‘Aphrodite’ is the fourth U.S. National Arboretum triploid cultivar of Hibiscus syriacus L., commonly known as rose of sharon. In the past, rose of sharon, although it flowered heavily in early summer when few other shrubs bloom, produced abundant seed and, subsequently, weed seedlings in the garden. The development of nearly sterile triploid cultivars eliminated the source of weed seedlings and elevated the plant to an elite summer flowering shrub. Triploid cultivars previously introduced are ‘Diana’, NA 32224 (1), with pure white flowers; ‘Helene’, NA 41786 (2), with white flowers and a prominent dark red eye spot; and ‘Minerva’, NA 54984 (3), with lavender flowers.
‘Minerva’ is the 3rd triploid Hibiscus syriacus L., commonly known as the ‘Rose of Sharon’, introduced by the U.S. National Arboretum. ‘Diana’(l), NA 32224, with pure white flowers and the first triploid introduction, and ‘Helene’(2), NA 41786, with white flowers and prominent dark-red eye spot, have become highly esteemed and are now the leading nursery cultivars. The introduction of ‘Minerva’ extends the color range to lavender and further elevates the ‘Rose of Sharon’ to an elite summer flowering shrub.
Hibiscus syriacus L., commonly known as rose of sharon or althea, is a plant which can endure extreme heat, drought, and poor soil to provide a freeflowering summer shrub. The landscape qualities of the species have been enhanced by the development of triploid cultivars with compact growth habit; leathery, dark green leaves; sterility; and abundant, continuous flowering throughout the summer. In 10 years ‘Diana’ (1), the first introduced triploid cultivar, has become highly esteemed and is now the leading cultivar grown by nurserymen.
The anthocyanins in the flowers of crapemyrtle (Lagerstroemia) species and cultivars are the 3-glucosides of delphinidin, petunidin, and malvidin. These three pigments are also present in most of the cultivars of rose of sharon (Hibiscus syriacus), but one cultivar contained cyanidin 3-glucoside as the major petal pigment Thus, the development of plants with “true-red” petals is remotely possible in rose of sharon but unlikely in crapemyrtle.
Five container substrates—3 pine bark (PB) : 1 peat (PT) : 1 sand (SD), 3 PB : 1 recycled paper (RP) : 1 SD, 2 PB : 2 RP : 1 SD, 3 vermiculite (VM) : 1 RP : 1 SD, and 2VM : 2 RP : 1 SD—were used to grow rose-of-sharon (Hibiscus syracus L. `Double Purple') and forsythia (Forsythia ×intermedia Zab. `Lynwood Gold') for 4.5 months. The control substrate (3 PB:1 PT:1 SD) had higher concentrations of NH4 * in leachate than other substrates at each of four sample times during the growing season except 4 Aug. Leaf number and leaf area per plant and height of rose-of-sharon were greater and the leaf area per leaf was smaller in all substrates containing recycled paper than in substrates without recycled paper. Forsythia plants had greater stem and root dry weights and were taller in substrata without recycled paper than plants in substrates with recycled paper. Processed recycled paper is a possible component for container nursery plant production, but further testing on a large number of species is needed before widespread implementation.
designated ratio but the same total volume. Using the NCGD system to study the responses of different plants to a specific range of salt concentrations can help define the salinity threshold for plant species. Rose of sharon, ninebark, and japanese spirea are
that produced plants with satisfactory quality and a marketable size by 13 Sept. 2013 were 1.05 kg·m −3 N for rose of sharon and 0.75 kg·m −3 N for ‘Palace Purple’ coral bells, bigleaf hydrangea, and ‘Magic Carpet’ spirea ( Fig. 1 ). ‘Green Velvet
WetEarth, a processed recycled newspaper product, was used in combination with pine bark, sand, and vermiculite as a growing medium for rose of Sharon and forsythia. Rose of Sharon was taller and had more leaves; more leaf area per plant; and greater leaf, stem, and root dry weights in all media containing recycled paper compared to plants grown in a medium consisting of 3 pine bark: 1 peat moss: 1 sand (by volume) (control). Forsythia grown in the control media were taller than those grown in any medium containing recycled newspaper. There was no difference in number of leaves per plant or leaf area of forsythia, regardless of growing medium. Physical and chemical properties of each medium also were investigated. All media containing recycled newspaper had a higher pH, porosity, and air space than the control medium.
An adventitious regeneration protocol developed for Hibiscus cannabinus L. (kenaf) was attempted on various ornamental hibiscus species. Hibiscus syriacus (Althea, Rose of Sharon) has been successfully regenerated using the kenaf protocol. Leaf tissue from two cultivars (`Double Pink' and `Diana'—a triploid) was placed on kenaf regeneration media. Adventitious shoots emerged from both cultivars within 8 to 10 weeks. Shoots were then excised and placed on a medium for rooting. Additional hibiscus species have been evaluated for regeneration ability. Previous studies with kenaf determined the adventitious regeneration protocol could induce mutations (somaclonal variation) in the regenerants. Variations in kenaf stem color and flower shape were noted. Since many ornamental hibiscus are asexually propagated, once a desired mutant is identified, it could be maintained and propagated without loss of the unique trait(s).