Border forsythia (Forsythia x intermedia), or golden bell, ushers in spring with its vivid golden yellow flowers and is one of the most recognized shrubs in the South. These hybrid forsythias are crosses between two species from Eastern China, Forsythia suspensa (Weeping Forsythia) and F. viridissima, (Greenstem Forsythia) and many excellent selections have been made, including dwarf and compact forms. These hybrids are adapted to all areas of South Carolina.
It grows 8 to 10 feet tall and 10 to 12 feet wide. It has an erect habit, with most canes growing upright. Some are weeping, creating a wild, unkempt look. The form varies depending on the variety.
Forsythia grows at a rapid rate and is long-lived.
The early spring flower is the most appealing feature of this plant. Flowers are usually profuse, and open before the leaves emerge on the plant. With an unusually mild winter, bloom may occur as early as late January, but usually occurs in March.
Flowers will last for two or three weeks unless killed by cold. The yellow flower color varies with varieties, ranging from pale to deep yellow. The flowers are 1¼ to 1½ inches long and wide, bell-like and produced in clusters. They bloom on last year’s wood. Dark green leaves emerge shortly after bloom. In the fall they may turn slightly yellow, maroon or purple, depending upon the cultivar and the amount of sunlight received.
Forsythias do not belong in areas where they must be kept in bounds, such as in foundation plantings, unless compact cultivars are chosen. They are best used as a specimen or in shrub borders and groupings. Forsythia may also be used to create a hedge and may be planted with a 3- or 4-foot spacing between plants.
Larger cultivars can become unruly and require some maintenance wherever they are grown.
The ideal soil is fertile, loose and well-drained, although it will tolerate almost any soil condition. Forsythia should be planted in full sun for maximum flowering. The forsythia hybrids compete successfully with the demanding roots of other shrubs and trees and transplant easily.
Prune in spring after flowering so that buds for the next year can develop in the fall. Potential flowers for the next year will be cut off if the plant is pruned after the buds develop. Pruning should not be a shearing process, but a thinning out of the older branches at the base of the plant, allowing the more vigorous branches to take over. They are often sheared to make a formal hedge or to reduce the size of the plant, but this detracts from the graceful habit of growth. They can be cut back to the ground and allowed to produce all new growth.
Forsythia can be forced to bloom indoors before it would normally occur outdoors. Between early January and late February, cut branches, bring indoors and place them in water. Flowers will open in about 10 days.
Like with most hardwood deciduous shrubs, softwood forsythia cuttings taken in late spring to early summer root easily. However, semi-hardwood cuttings taken later in the summer will also root easily.
Serious problems are infrequent with forsythia in South Carolina. The most common problem is with Phytophthora root rot, which may occur when forsythia is planted in a poorly drained soil. Prevention is the key; plant forsythia in well-drained soil. Botryosphaeria canker can be a problem on any woody shrub under extended drought conditions. Prune out any dying branches and dispose of prunings. Water plants weekly to reduce the chance of infection and to encourage good growth. Phomopsis gall is not common, but more frequently occurs on forsythia than other types of shrubs. Phomopsis galls are spherical nodules or protuberances that cluster along a branch and cause branch dieback. They are most noticeable during winter. Prune out infected branches and dispose of prunings.
- ‘Beatrix Farrand’ – This 8- to 10-foot-tall shrub has vivid golden yellow flowers. This cultivar is a F. x intermedia selection that was chemically treated to become a tetraploid, and then the result was backcrossed with F. x intermedia again to make a triploid forsythia. It is generally superior to other forsythia cultivars in flower size, vigor, and general habit.
- ‘Karl Sax’ – This is shorter (to 6 feet tall) and has a bushier habit than ‘Beatrix Farrand.’ It has golden yellow flowers, and blooms about 2 weeks later than other forsythias. This cultivar is a tetraploid (i.e., with twice the normal chromosome count).
- ‘Lynwood’ – This has an upright growth habit, a heavy bloomer, and has bright yellow flowers, although slightly lighter yellow than the species. Grows 8 to 10 feet tall and 6 to 8 feet wide. Sometimes listed as ‘Lynwood Gold’.
- ‘Northern Sun’ – This is a very cold hardy cultivar that grows to 10 feet tall and 9 feet wide and produces clear yellow flowers. It is a hybrid between the very hardy Korean Forsythia ovata and F. europaea and is hardy to USDA zone 4.
- ‘Northern Gold’ – This large cultivar has an upright spreading habit and grows to 6 to 8 feet tall and 5 to 7 feet wide. The flowers are golden yellow.
- ‘Spectabilis’ – This shrub, known as Showy Border Forsythia, is one of the best of the original Forsythia x intermedia crosses and is the standard by which new cultivars are compared. It is vigorous and grows 10 feet tall and wide. The flowers are bright yellow.
- ‘Spring Glory’ – This cultivar is a strong grower to 10 feet tall. It flowers abundantly with deep yellow blooms.
- ‘Arnold Giant’ – This compact golden bells cultivar grows to 5 feet tall and wide. It is a tetraploid plant from a seedling of the cultivar ‘Spectabilis’. ‘Arnold Giant’ has larger, thicker, and darker green foliage than other cultivars, and the shrub habit is more upright.
- ‘Show Off’ – This cultivar grows to 5 to 6 feet tall, has bright yellow flowers on stems that make good cut flower displays.
- ‘Sunrise’ – This cultivar grows to 5 feet tall and wide, has an attractive mounding habit that has a more compact growth habit, and has maroon fall color.
Smaller, More Compact Cultivars:
- Golden Peep™ – This cultivar is from the French breeding program, has a dense dwarf form, and grows to 18 to 30 inches tall and 36 inches wide.
- Goldilocks™ – This cultivar is a dwarf that has upright spikes of golden yellow flowers. It grows to 24 to 36 inches tall and wide.
- Gold Tide™ – This cultivar has lemon yellow flowers and grows to 24 to 30 inches tall and 4 feet wide.
- ‘Happy Centennial’ – This compact cultivar grows to 24 to 30 inches tall and 3 to 5 feet wide. The flowers are light yellow. May be used as a groundcover.
- ‘Show Off Starlet’ – This cultivar has a compact growth habit, deep yellow flowers and maroon fall color. It grows to 2 to 3 feet tall and 3 to 4 feet wide.