The genus Viburnum encompasses a diverse group of shrubs and small trees valued in landscaping for their attractive foliage, flowers, and berries. The growth rate varies significantly between species, meaning there is no single answer to how fast they grow. A plant’s inherent genetic potential, coupled with local environmental conditions, dictates the speed at which it establishes and matures. Understanding these variables helps in selecting the right plant for a desired landscape outcome, such as a quick privacy screen or a slow-growing accent shrub.
Categorizing Viburnum Growth Rates
The horticulture industry uses standardized categories to classify the speed at which a shrub increases in height and width each year. These classifications provide a reliable framework for managing growth expectations after planting. A slow grower typically adds 12 inches or less of new growth annually. Species exhibiting a moderate growth rate put on between 13 and 24 inches of growth per year under favorable conditions. A fast grower averages 25 inches or more of growth annually, and these varieties are often chosen for creating hedges or privacy screens quickly.
Species-Specific Growth Profiles
The growth rate of any viburnum is primarily determined by its specific genetics. The Mapleleaf Viburnum (Viburnum acerifolium) is a naturally slow-growing native species, often reaching a mature height of only six feet over many years. Dwarf cultivars, such as ‘Mrs. Schiller’s Delight’ of Walter’s Viburnum, are also programmed for minimal annual growth, making them suitable for small spaces.
Many widely planted varieties fall into the moderate category, achieving a steady rate of 12 to 24 inches annually. The popular Korean Spice Viburnum (Viburnum carlesii) and Viburnum suspensum are moderate growers that establish themselves reliably. This rate allows them to fill out a garden space in a reasonable timeframe while requiring minimal corrective pruning. For gardeners seeking rapid establishment, certain species are known for their fast growth profile, often exceeding two feet in a single season.
The Sweet Viburnum (Viburnum odoratissimum) is a prime example of a fast grower, frequently chosen for quickly creating dense, tall hedges. Another fast-growing screening choice is the hybrid Prague Viburnum (Viburnum × pragense), which rapidly develops an upright, oval form.
Optimizing Conditions for Maximum Growth
While genetics set the potential speed, a plant will only achieve its maximum growth rate when its environmental needs are fully met. Light is a significant factor, as most varieties thrive in full sun, meaning at least six hours of direct sunlight daily. Although many can tolerate partial shade, reduced light often results in a slower growth rate and less prolific flowering and fruiting.
Soil quality and moisture management are also important for robust growth. Viburnums prefer well-drained, slightly acidic soil, though they are adaptable to various soil types. Planting in poorly drained soil where water collects can severely inhibit growth and lead to root rot. During the establishment period—the first one to two years after planting—consistent moisture is necessary to develop a strong root system.
Studies show that providing frequent irrigation, such as every two to four days during the establishment phase, can significantly enhance canopy growth. Once fully established, the plant’s water needs decrease, and it becomes more tolerant of dry spells. The application of fertilizer can support growth potential, especially in poorer soils. A light application of a general-purpose fertilizer or organic matter in early spring can encourage strong new growth.