Why did the northern Sophora japonica grow wildly this summer?

Probably because of the influence of climate.

From spring to early summer this year, there was little precipitation in the north, especially drought, which inhibited the vegetative growth of Sophora japonica and promoted the reproductive growth, resulting in a particularly large flowering volume.

Sophora japonica originated in China, also known as Sophora japonica. Mainly distributed in North China, Northwest China, Northeast China and other regions, it can grow in the plains and Loess Plateau with an altitude of 1 m, and even live well in mountainous areas with little water. Sophora japonica blooms from June to August, and bears fruit at1-1.