Autumn leaves: why yellow and red differ

Chlorophyll makes a growing leaf look green. As it breaks down during senescence, yellow carotenoids already present in the chloroplasts become more conspicuous. Ginkgo is a familiar example. A yellow leaf is not simply a leaf that failed to progress to red: species differ in their capacity to produce particular pigments.

Anthocyanins accumulate in the cells of reddening leaves. Their timing and quantity interact with the decline of chlorophyll, producing different shades and mixtures of green and red. Reddening does not require a yellow stage: the loss of chlorophyll and accumulation of anthocyanins can overlap.

Trees recover some nutrients from ageing leaves. Cells in a thin layer at the junction of leaf stalk and branch change and break down, allowing the leaf to detach. Light and temperature affect the process, but different leaves and trees do not move in step. Evergreen trees also replace old leaves, usually without the conspicuous whole-tree synchrony of deciduous woodland.

The function of anthocyanins in ageing leaves remains a research question. A 2024 Forestry and Forest Products Research Institute account describes a study of Acer japonicum, a Japanese maple. In this species, producing anthocyanins consumes sugars, limiting their accumulation and helping to avoid early leaf fall and damage from reactive oxygen. Anthocyanins may serve different functions in other species.

Leaf shape helps identify a tree; colour records a changing condition. One leaf can retain green areas while other parts redden. Different exposure to light also contributes to variation within a crown. Maples, ginkgo and persimmon can all contribute to an autumn landscape, each with different pigment changes.

Temperature also shifts the timetable. Japan Weather Association’s 2026 explanation says cooler autumn conditions tend to advance the viewing season, while warmer conditions delay it. Its forecasts use historical relationships between local maple-colouring dates and temperature; higher-elevation sites can colour earlier than a locality’s general forecast.

Autumn viewing in literature

Autumn viewing appears in Heian literature under the name momijimi: examples occur in The Tale of Genji and the Shūishū poetry anthology. Literary scholar Naoto Yoshikai identifies an early use of the now familiar name momijigari in the Kamakura-period Fuboku Wakashū. The practice appears in these texts earlier than the name momijigari.

Viewing recorded in a painted scroll

The Naegi Toyama Historical Museum describes an 1834 copy commissioned by Toyama Tomohisa of a scroll depicting a visit to Takao in 1823. Aoyama Shingo supplied the writing and Sasaki Katsubei the painting, alternating poems, pictures and prose. For maple trees, the Japan Meteorological Agency records the first day when most leaves on a designated tree have turned red. It does not mean the first red leaf or simultaneous colour across a mountain.

Modern parks and weather observation

Modern parks gave established scenery a new public setting. Osaka Prefectural Park Association dates Minoh Park to 1898 and notes that visitors were already calling the area a park around 1887. Its waterfall, ravine and autumn foliage became part of a managed park. A separate development made seasonal change comparable across sites: the Japan Meteorological Agency adopted nationally uniform biological-season observations in 1953. Changes around observation stations later made some species difficult to monitor. Its reduced programme, introduced in 2021, retained maple colouring and leaf fall, as well as ginkgo yellowing and leaf fall.