They are deciduous trees 12–15 m (40–50 ft) tall, with large leaves 15–40 cm across, arranged in opposite pairs on the stem. The flowers are produced in early spring 10–30 cm long and resembling a foxglove flower.
From Wikipedia: Paulownia is extremely fast growing; some species of plantation Paulownia can be harvested for saw timber in as little as five years. Once the trees are harvested, they regenerate from their existing root systems, earning them the name of the "Phoenix tree." Paulownia has the ability to reclaim ecologically stressed and degenerate patches of land relatively quickly. Its root systems run deep and penetrate compacted and contaminated soils which have resulted from industrialized development. Paulownia is a phyto-remediator, increasing the organic content of degraded soils, processing and filtering contaminants through the uptake of its vascular system, and emitting oxygen into the atmosphere.