Therefore, it is best to avoid highly exposed areas with strong wind when choosing sites for afforestation. Soil Paulownia has a very wide natural distribution in China and has been successfully introduced over large areas. It grows well on the rich humus soil in the temperate zone, on the dry poor soil on the north central China Plain, on the rich forest soil in Szechuan Basin in the northern subtropics, on the claye soil in the subtropics, on the laterite in the tropics of southern China, and on the carbonate drab soil of loess parent material on the dry steppe of western China. Paulownia is found mostly on sandy and clayey soil-heavy earth. The clay content of the soil on which the different species are found varies.
Most Paulownia species are deep rooted with well developed lateral roots.
The extension of the root system requires not only suitable water and temperature conditions, but also deep, loose, moist and well-aerated soil. On excessively clayey soils, P. fortunei , P. tomentosa , P. albiphloea and P. albiphloea var. Paulownia is sensitive to the depth of the underground water table and to soil salinity. The water table should generally be below 1.5 m depth and stagnant water for three to four days can prove fatal. P. fortunei can attain an annual average diameter increment of 3.6 - 4.2 cm.