Wisteria is an ornamental plant prized for its sweeping, fragrant clusters of flowers that appear in spring and early summer. The vigor of this woody plant creates a breathtaking display, often covering large structures with dense foliage and cascading blooms. Because of this rapid growth, the size of a mature wisteria is a major consideration for any property owner planting one. Understanding the plant’s true growth habit is the first step in managing its potential.
Wisteria’s Growth Habit
The common perception of a “wisteria tree” is misleading because the plant is botanically a woody, deciduous vine. It is classified as a twining climber, meaning its stems wrap tightly around any available support structure. This aggressive twining nature necessitates a robust support system, such as a heavy-duty pergola, arbor, or steel cable. Mature stems can become thick and heavy enough to crush standard wooden lattices or damage gutters and drainpipes.
The popular “tree” form is achieved entirely through rigorous training and pruning, not through natural growth. This process involves selecting a single, strong stem to serve as a trunk, staking it securely, and continuously removing all side shoots until the trunk is thick and self-supporting. The crown is then allowed to develop at a desired height, resulting in a free-standing standard that mimics a tree shape. This trained form still requires ongoing maintenance to prevent the vine from reverting to its natural, sprawling habit.
Typical Heights and Spreads
The size a wisteria reaches depends heavily on its species, with the most common varieties exhibiting distinct growth patterns. The Asian species, Chinese wisteria (Wisteria sinensis) and Japanese wisteria (Wisteria floribunda), are known for their massive scale. Chinese wisteria can grow vigorously, reaching lengths of 20 to 40 feet, with a lateral spread extending up to 30 feet if left unchecked. Japanese wisteria is similarly substantial, often climbing to heights of 30 to 35 feet or much longer over a supportive structure.
The American wisteria (Wisteria frutescens) is a significantly more compact and less aggressive native alternative. This species typically grows to a height of 15 to 30 feet, with a lateral spread contained to 4 to 8 feet. While all wisterias can be trained into a tree standard, the species’ vigor dictates the ultimate size and weight of the crown it can support. For example, a trained Chinese or Japanese variety will still have a massive, heavy canopy compared to the American species.
Environmental Factors Affecting Size
Wisteria’s potential for size is realized only when optimal environmental conditions are met, particularly regarding light and soil. The plant performs best and achieves its maximum growth rate when it receives full sun (at least six hours of direct sunlight per day). Insufficient light will reduce the size and density of the plant and severely inhibit its ability to produce abundant flower clusters.
Soil quality also plays a direct role in determining the plant’s size and vigor. Wisteria thrives in deep, fertile, and well-drained soil, which provides the necessary nutrients and anchorage for rapid growth. While adaptable to various soil types, poor drainage can lead to root issues, severely stunting growth and compromising health. Furthermore, a long, warm growing season will extend the period of vegetative growth, allowing the plant to add more length and bulk annually than it would in a region with a short, cool summer.
Controlling Wisteria Growth
Managing a wisteria’s size is an ongoing process that requires diligent, twice-yearly pruning to maintain its shape and encourage flowering. The primary method for control is structural pruning, which establishes the permanent framework. In late winter or early spring, before buds open, all lateral shoots from the previous year’s growth should be cut back severely, leaving only two to three buds on each spur. This targets the plant’s energy toward flower bud development rather than long, vegetative stems.
A second, equally important pruning should occur in mid-summer, typically after the plant has finished blooming. This summer pruning involves cutting the long, new, whippy green shoots back to about six inches in length, leaving five or six leaves on each shoot. This practice helps restrict the vine’s rampant spread during the growing season and improves light penetration to the main framework, assisting in ripening the wood for the next year’s blooms. For extremely vigorous plants, root pruning can be employed to control overall vigor by physically slicing into the soil around the plant’s base in the fall to sever some feeder roots.