A wax myrtle may grow up to five feet in height and width in a single growing season, making it among the fastest-growing hedge plants. This durable plant is a broadleaf evergreen with inconspicuous flowers. Clusters of grayish white berries, which are an eighth-inch in diameter, appear in late summer. A wax myrtle plant is either male or female. Only the females produce fruit.
The northern bayberry, a deciduous or semi-evergreen shrub, also tops the fast-growing list. This bayberry has shiny dark green leaves, while its silvery gray berries provide winter interest. It is related to the wax myrtle, though more tolerant of cold. The northern bayberry grows at a rate of 12 to 18 inches per year with a mature height of about 9 feet and similar width.
With its early flowers appearing even before leaves emerge, the forsythia offers cheery bursts of yellow announcing spring's arrival. Flowers last 10-14 days and are followed by medium to dark green leaves. Mature forsythias may be 8 to 10 feet tall. Though forsythias are fast and easy-growing, they do require some pruning. The University of Iowa recommends pruning a mature shrub by cutting a third to a fourth of the largest stems to ground level every other year.
Clavey's Dwarf Honeysuckle
A broad, dense plant with medium green leaves, Clavey's Dwarf Honeysuckle is another fast grower. This honeysuckle grows to about five feet. It produces white flowers in spring followed by bright red berries, which attract wildlife.
Several characteristics make the Chinese lilac suitable for informal hedges: fast growing, compact, low-maintenance, and nonsuckering. This variety of lilac has large clusters of fragrant lavender or purple flowers. It grows to a height of 10 feet.