What is the flower of a tree with many colorful balls growing on its branches?

That is the silver bud willow.

Silverbud willow is a willow plant of the willow family, deciduous shrubs, 2-3 meters high. Branches greenish brown, slightly reddish, sericeous when young, and then fall off. Leaves long elliptic, 9-15 cm long, margin serrulate, leaf abaxial surface densely covered with white hairs, subleathery. Male inflorescences elliptic reticulate, 3-6 cm long, opening in early spring before the leaves, in full bloom the inflorescences are densely covered with silvery-white sericeous hairs. The inflorescence is densely covered with silvery-white sericeous hairs when in full bloom.

Silver willow mainly cut its branches with flower buds for ornamental applications, is a traditional Chinese folk winter flower arrangements. Its silver-white brush-like buds and purple-red bracts, like a little girl in a red dress, beautiful and lovely; bracts showing smooth hairy buds, the posture is more noble and elegant, and its buds ornamental period in the Spring Festival period, coupled with the silver willow and the "silver two" resonance, representing good luck, the wealth of the meaning of the silver willow cut branches are widely loved by the people. The cut branch can be kept in water, and it can be used as an ornamental plant. The cut branch can be kept in water, the ornamental period can reach more than 2 months, dry insertion is longer; both can be alone in a bottle, can also be used as a flower arrangement with material.