Botanical Characteristics

Root System

Paulownia is a tree with deep roots and a well-developed root system. Upper roots are thin, sharp, branched into two and grow very dense. The intake / absorbing roots are approximately 1-5 mm thick and can extended to more than 60 cm. The development and spread of the root system is influenced significantly by the groundwater level, the physical characteristics of the soil and the available nutrients. Paulownia is most suited to light mechanical composition soil with good drainage. Usually there are several strong and large roots that grow on the sides and down and the shape of serrations.

The spread of the roots of a tree can reach up to 30 m long with a diameter of about 28 m, which is about 3 times more compared to the crown of the tree. Around 70-85% of absorbing roots spread in a radius within 40-100 cm.

Crown

Paulownia is a deciduous tree reaching a height of 12-16 meters, and sometimes over 20 meters. The crown is open and dome-shaped, consisting of relatively few branches, which often start very close to the soil. The bark is smooth and delicately striated, reddish-gray color in young trees and clear gray shade in older trees.

The growth of the crown is a function and continuation of the branches that grow each year. The top, as well the secondary and third pairs of buds can be damaged by frosting during the winter. In the spring the following fourth and fifth buds, which usually are not affected by the cold, develop new branches. Then the second and third pairs of buds formed from the new branches fail again during the next winter and the fifth and sixth pairs of buds produce an outgrowth and form new branches in the spring. The growth of the crown follows this pattern year after year. The number of new branches formed and the morphology of the crown determine the age of the tree.

The leaves are heart-shaped, toothed, slightly stained mossy fibers from the upper side and densely covered with moss on the bottom side. They are with size 35 x 25 cm and a length of 10-15 cm. Under the right conditions of development leaves can reach up to 75 cm in diameter.

The flowers are from white and pale violet to prupule-blue, with the form brittle harebell, reaching a length of up to 6 cm, arranged in flower clusters long 20-30 cm. The fruits grow on the shaft egg-shaped, light green in color and sticky in touch. Their size is approximately 3 x 1.8 cm, at each flower cluster grow up to 2-10 petals, each of which has 2 partitions containing seeds from 3 to 5 mm.

Reproduction

The Paulownia gives fruits regularly from age 15 onwards. In eastern and southern United States flowers appear in April and May before the leaves appear. Fruit start browning in the fall, when they ripen and remain on the tree throughout the whole winter. It propagated by seeds and root sprouts.

The seeds germinate within 20-30 days after sowing. Germination rate is 85-93% at 4 ˚С. There are between 4 and 6 million seeds / kg or about 6200 seeds / g. Under favorable conditions a large tree can produce more than 20 million seeds annually. It grows very quickly.

A stem grown from the seeds reaches a height of 3-4 m at the end of the first year, with a diameter of 3-5 cm at the base. Parent can reach a height of 4-5 m and sometimes 8 m after one year.

Wood can be easily propagated vegetatively, using root cuttings. Immature plants remain in the nursery, being pruned after changing their leaves and replant in the field a year later. It is recommended the planting on the field to be done with young plants 4-5 m high and with a diameter below the crown of 4-6 cm. Paulownia is a species that requires direct sunlight and thus, young seedlings should be protected from weeds during the first 1-2 years.