Border forsythia is a multi-stemmed shrub noted for the bright yellow flowers in early spring. A good shrub for mixed borders, en masse, or as an informal hedge. Since flower bud hardiness varies by cultivar, it is best to choose a zone hardy cultivar.
Size & Form:
Border forsythia is an upright to rounded, multi-stemmed shrub with irregular, arching stems reaching eight to 10 feet high and wide. There are many cultivars available in a wide range of heights.
Native geographic location and habitat:
It is of hybrid origin (Forsythia suspensa x Forsythia viridissima).
Bark color and texture:
The bark is tan to light brown with four-sided, prominent lenticels. The pith is solid, but internodes are chambered.
Leaf or needle arrangement, size, shape, and texture:
Forsythia has opposite lanceolate leaves that are 3 to 5 inches long and 2 to 3 inches wide. The upper half of the leaf has serrated margins. The leaf is medium green in summer and changes to yellow-green, sometimes with a tint of purple, in the fall. This shrub holds its leaves late into fall.
Flower arrangement, shape, and size:
It has a simple, four-petaled, bell shaped yellow flower. They are 1 1/4 to 1 1/2 inches long in clusters of two to six along older stems. This shrub will typically flower in late March into April before the leaves emerge.
Fruit, cone, nut, and seed descriptions:
This shrub has a dehiscent brown capsule winged seed.
Border forsythia will have less blooms when planted in partial shade, so for best blooming potential, grow this shrub in full sun. Forsythia has a fibrous, spreading root system that grows best in moist, well-drained soils. It is adaptable to a wide range of soil types, including poorly drained wet sites. This shrub is drought tolerant once established although it will benefit with a layer of mulch to moderate soil temperature fluctuations.
Flowers are produced on old wood, so forsythia should be pruned immediately after flowering. Overgrown shrubs can be rejuvenated by cutting to the ground in the fall. Arching branches can produce new roots if touching soil. Flower buds may be injured in extremely cold winters or early spring cold snaps after plants come out of dormancy. Choose zone hardy cultivars.
List of pests and diseases:
Leaf spots, crown gall, and spider mites can all affect the shrub. None are a serious problem. This shrub is tolerant of black walnut toxicity, deer, wet sites, and salt.
Gold Tide™ border forsythia (Forsythia x intermedia ‘Courtasol’):
A dwarf form reaching 1 1/2 to 3 feet high and 4 to 5 feet wide. It has light yellow flowers and can be used as a ground cover.
Golden Peep™ border forsythia (Forsythia x intermedia ‘Courdijau’):
This cultivar has a compact, rounded form reaching 1 1/2 to 2 1/2 feet high with bright yellow flowers. The leaves tinge purple in the fall.
Lynwood border forsythia (Forsythia x intermedia ‘Lynwood’):
A popular upright form reaching 6 to 8 feet high. This cultivar is considered a very heavy bloomer with a bright yellow flower that opens widely and is well distributed along the branch. The fall leaf color is yellow with a purple tinge.
Show Off border forsythia (Forsythia x intermedia ‘Mindor’):
It has an upright to rounded form and grows 5 to 6 feet high and wide. The bell-shaped flowers are lemon yellow along the stems.
Spectabilis border forsythia (Forsythia x intermedia ‘Spectabilis’):
A large, vigorous grower reaching 10 feet tall with bright yellow flowers that are borne in the leaf axils. This is one of the hardier hybrids.
Spring Glory border forsythia (Forsythia x intermedia ‘Spring Glory):
This is an 8 to 10 feet high shrub with abundant deep yellow blooms. The flower buds are susceptible to late season frost.