Forsythia is a popular, early-blooming deciduous shrub known for its spectacular display of bright yellow flowers that arrive before its leaves in early spring. It is a favorite in many landscapes due to its simple care requirements and general hardiness. Gardeners often seek this plant for a burst of color, but its reputation for vigorous growth requires understanding its growth habit for successful incorporation into any design.
Defining the General Growth Rate
Forsythia is classified as a fast-growing shrub, establishing itself quickly in the landscape. The typical annual growth rate for most common varieties is substantial, usually falling within a range of one to two feet (30 to 60 centimeters) per year.
Growth speed is highest after the plant becomes established, typically after the first one or two seasons in the ground. During the initial phase, the plant focuses energy on developing a robust root system rather than adding significant height or spread. Once the roots are secure, the shrub’s fast-growing nature fully expresses itself, often requiring regular attention to manage its size.
Impact of Cultivar Type on Speed
The ultimate size and speed of growth are heavily influenced by the specific cultivar a gardener selects. Larger, classic cultivars, such as ‘Spectabilis’ or ‘Lynwood Variety,’ are the fastest growers and can reach ten feet tall and twelve feet wide if left unpruned. These types are well-suited for creating large screens or informal hedges where robust growth is an advantage.
In contrast, modern breeding has produced dwarf or compact varieties for smaller spaces and less maintenance. Cultivars like ‘Gold Tide’ or ‘Show Off Starlet’ exhibit a significantly slower growth rate and a smaller mature size, often staying under four feet in height and spread. These smaller forms allow gardeners to enjoy the characteristic yellow blooms without the high-speed growth of their larger relatives.
Optimizing Conditions for Maximum Growth
To achieve the maximum annual growth potential of one to two feet, forsythia requires specific environmental inputs. Full sun exposure is necessary, as the shrub needs at least six hours of direct sunlight daily to fuel vigorous growth and abundant flowering. Plants grown in partial shade will exhibit a slower, more straggly growth habit and produce fewer flowers.
The shrub thrives best in fertile, well-drained soil, though it is adaptable to various soil types, including clay. Consistent moisture, especially during the first two years after planting, helps establish the deep root system that supports rapid growth. Amending the soil with organic matter, like compost, improves fertility and drainage, helping the shrub quickly reach its full potential.
Controlling Size Through Pruning
Given the forsythia’s fast growth, managing its size is necessary for maintaining an attractive, healthy shrub. Pruning should occur immediately after the flowers fade in the spring, which prevents removing next year’s flower buds that form on the current season’s growth. Pruning must be completed by mid-summer to allow the shrub sufficient time to develop new wood for the following spring’s bloom.
The most effective size-control method is thinning, which involves removing up to one-third of the oldest, thickest canes down to the ground. This technique opens the center of the shrub, encourages new, vigorous growth from the base, and maintains the plant’s natural, arching form. Avoid using hedge shears to shear the top and sides, as this results in dense, unattractive growth and significantly reduces the number of flowers.