In Autumn deciduous trees shed their leaves, which first become red, brown or yellow in colour. Most commonly depicted are maple leaves. Oak and ginkgo leaves may be seen as well.
Japanese word: 紅葉 (Momiji or Kouyou) or 椛 (Momiji)
NOTE: 'Momiji' has two meanings. One of them means various kind of autumn leaves in general. The second one is another expression about Kaede (maple trees).