[Answer] What do Japanese call their colorful autumn leaves?

Step 1 : Introduction to the question "What do Japanese call their colorful autumn leaves?"

...When autumn arrives in Japan, the colorful autumn leaves, or 'koyo,' brighten the countryside. The brilliant colors of red, orange, gold and yellow draw as many visitors as the world-renowned cherry blossoms do in the spring. Taking time to view the autumn leaves is a popular outing in Japan today, just as it has been for centuries. Famous spots that offer breathtaking views of the fall foliage dot the country, especially in the mountainous regions, in parks, and around temples. Weather permitting, viewing is possible from September through early November. Source: jnto.org.au

[Ans] By what word was the autumn season known before the 16th century?

Step 1 : Introduction to the question "By what word was the autumn season known before the 16th century?"

Before the season between summer and winter was "autumn" or "fall," it was a time called "harvest." It was common to call the season autumn in English in the 12th century. In the 14th century, the practice of calling the season "autumn" or "fall" spread. It isn't clear where the habit of naming the season "fall" originated but most think it came from the idea of trees shedding their leaves. "Fall" as the name of the season made its way to the New World in the 17th century and remains the preferred season name in the U.S. Source: MentalFloss.com

[Ans] What color are the leaves of birch, tulip poplar, redbud and hickory trees in autumn?

Step 1 : Introduction to the question "What color are the leaves of birch, tulip poplar, redbud and hickory trees in autumn?"

When the leaves of trees such as redbuds, birches, tulip poplars and hickory always turn yellow in the fall, never red. There is apparently no biological significance or function to the shift in color. There are a few trees, such as dogwoods, black gums, sugar maples and sourwoods that usually turn red but they may, on occasion, be yellow as well. The most intense color shifts in fall foliage take place in areas such as New England in the northeastern U.S. Source: NCNatural.com