Paulownia tomentosa, commonly known as the Empress Tree or Foxglove Tree, is a fast-growing deciduous tree celebrated for its striking appearance. It features large, heart-shaped leaves and produces beautiful, fragrant purple flowers in early spring before the foliage. Its ornamental value and rapid establishment make it a popular choice for gardeners seeking aesthetic appeal and shade.
Understanding Paulownia Tomentosa
Paulownia tomentosa originates from central and western China, where it has been cultivated for over a thousand years. This tree is renowned for its fast growth rate, adding up to 15 feet in a single growing season and reaching 50 feet within a decade. It is a hardy species, tolerating a range of conditions once established.
Beyond its ornamental appeal, Paulownia tomentosa holds significance for timber production due to its lightweight, strong, and durable wood, often used in furniture and musical instruments. However, it has gained a reputation as an invasive species in certain regions, particularly in parts of the eastern United States. Its prolific seed production and ability to resprout from roots contribute to its rapid spread in disturbed areas, posing a concern for native ecosystems.
Planting and Site Selection
Establishing Paulownia tomentosa begins with careful site selection. This tree thrives in full sun, requiring at least six hours of direct sunlight daily for optimal growth and flowering. While it can tolerate some light shade, sunny conditions consistently yield the best results.
The ideal soil is well-drained, rich in organic matter, and ranges from sandy to loamy, with a slightly acidic to neutral pH between 5.5 and 7.5. Heavy clay soils are not recommended, as poor drainage can lead to root rot; amending with compost or planting in a raised bed can improve conditions. Select a site that offers protection from strong winds, especially for young trees, as their rapid, succulent growth can be vulnerable to damage.
The best time to plant is typically early spring or autumn when the soil is workable. Dig a hole at least twice the width of the root ball and the same depth, allowing ample space for roots to spread. Position the tree so the root collar, where the roots meet the trunk, sits at soil level. Backfill gently, firming the soil to eliminate air pockets, and water thoroughly to help settle the soil.
Ongoing Care Essentials
Consistent moisture is particularly important for young Paulownia tomentosa trees, especially during their first growing season. Deep watering once a week is generally recommended, allowing the soil to dry slightly between waterings. Once established, the tree becomes more drought-tolerant but benefits from regular watering during prolonged dry spells.
For optimal growth and vibrant blooms, a balanced fertilizer should be applied in early spring as new growth commences. A slow-release granular fertilizer, such as a 10-10-10 N-P-K ratio, is often ideal, providing nutrients gradually throughout the growing season. Over-fertilization, particularly with excessive nitrogen, should be avoided as it can promote excessive foliage growth at the expense of flowering and may make branches more susceptible to frost damage. If the soil is already rich in organic matter, additional fertilization may not be necessary.
Paulownia tomentosa is hardy in USDA zones 5B through 9, capable of withstanding temperatures as low as -13°F (-25°C) when fully dormant. Young trees and seedlings are more susceptible to frost damage, especially if actively growing. Good soil drainage is paramount, as waterlogged conditions can quickly lead to root rot.
Pruning and Growth Management
Pruning is an important aspect of caring for Paulownia tomentosa, especially given its rapid growth. The best time to prune is typically in late winter or early spring, just before new growth begins. This timing allows the tree to recover quickly from pruning cuts.
Different pruning techniques can be employed depending on the desired outcome. For ornamental trees, light pruning helps maintain shape and encourages a bushier growth habit, while removing dead, damaged, or crossing branches improves air circulation and light penetration. Coppicing, or cutting the tree back to the ground, is a method used to manage size, encourage larger foliage, or for timber production. When coppiced, the tree resprouts vigorously, and a strong central leader can be selected to form a new trunk.
Common Issues and Solutions
Paulownia tomentosa is generally resilient to many common plant problems, but occasional issues can arise. Pests such as aphids and leaf spots may sometimes affect the tree. Regular inspection for signs of infestation or disease helps in early detection and management.
Maintaining good air circulation through proper spacing and pruning, along with overall tree health, contributes to preventing problems. Environmental stressors like drought can cause wilting, while nutrient deficiencies may lead to stunted growth or discolored leaves. Adequate watering during dry periods and balanced fertilization address these issues. Root rot can occur in waterlogged conditions, making well-draining soil and careful watering practices crucial for prevention.
Winter Care
Preparing Paulownia tomentosa for colder months is particularly important for young trees. While mature trees are relatively hardy, young plants benefit from some winter protection. Applying a layer of mulch around the base helps insulate the roots and retains soil moisture, providing a buffer against freezing temperatures.
In regions experiencing particularly cold weather or in marginal hardiness zones, wrapping young trees with horticultural fleece can offer added protection against frost and harsh winds. Watering adjustments are also necessary; as the tree enters dormancy in the fall, the watering schedule should be reduced, allowing the soil to dry between waterings. This helps prevent root issues during the colder, inactive period.