Why Ginkgo Turns Yellow and Momiji Turns Red: A Japanese Gardener's Notes on Autumn Leaves
In November, Japan's gardens and streets change colour. Ginkgo trees turn a clear gold, and Japanese maples, called momiji, turn red. Both trees drop their leaves in the same season, yet their colours are different.
The difference is not just about the kind of tree. It is about what is happening inside the leaf. One colour simply appears. The other is made.
We are a small tree care and landscape business in Mie Prefecture, central Japan. We prune maples and ginkgo in the gardens we look after every year, and this page explains what we see from the garden side.
Yellow was there all along
A leaf looks green because chlorophyll, the green pigment, is present in large amounts. But the same leaf also holds carotenoids, the yellow and orange pigments. They are there from the start, hidden under the green.
In autumn, the days get shorter and the air gets cooler. The tree stops making new chlorophyll and the green breaks down. As the green fades, the yellow that was always there shows through.
This is why ginkgo turns yellow. The gold is not a new colour. It was in the leaf the whole summer. The US Forest Service puts it simply: because carotenoids are always present, the yellows stay fairly constant from year to year.
Red is made in autumn
Red works the other way.
Before a deciduous tree drops a leaf, it forms a layer of cells at the base of the leaf stalk to separate the leaf from the branch. Once this layer forms, the sugars the leaf has made can no longer move back into the branch. They stay in the leaf.
With that trapped sugar, and with sunlight, the leaf makes a new red pigment called anthocyanin. That is the red of momiji.
So yellow appears by subtraction, and red is created by addition. They look like the same autumn colour, but they are opposites.
One tree, different colours
Here is something we notice in our customers' gardens every year. Even on one maple, the colour is not even. The branches on the south side turn a deep red, while the branches inside the crown or on the north side stay orange or yellow-green.
Red needs light. Anthocyanin is made with sunlight, so the branches that get the most sun turn the deepest red. A tree with crowded branches, where light cannot reach the inside, often drops its leaves before the red fully comes out.
Ginkgo rarely shows this. Its yellow is not made but revealed, so sun and shade make less difference. In the same garden, the ginkgo is reliably yellow every year, while the maple changes from year to year.
Two words that sound the same
Japanese has two ways to write autumn leaves, and both are read koyo. 紅葉 uses the character for crimson and means red leaves. 黄葉 uses the character for yellow and means yellow leaves. The difference you see in the trees is written into the language.
The word momiji itself was once a verb. In the Nara period, more than 1,200 years ago, people said momitsu, meaning to turn colour, and its noun form became momiji. Because Japanese maples colour so beautifully, the word came to mean the maple tree itself. Going out to view autumn leaves is called momijigari, literally "momiji hunting", and it is one of the classic outings of the Japanese autumn.
Japan officially records both trees
The Japan Meteorological Agency keeps a record of seasonal changes in plants at weather stations across the country. Each station watches the same chosen tree every year. The day a maple turns red is the first day most of its leaves look red when you view the whole tree. Ginkgo has its own yellow day, judged the same way.
In 2021 the agency cut its plant observations to six species. The maple's red leaves and the ginkgo's yellow leaves both stayed on the list, alongside cherry and plum blossoms. These two trees are how Japan measures the arrival of autumn.
Getting better red in a garden
Red leaves come out best with sunny days and cold nights. In a garden, what decides this is often not the maple itself but what is around it.
A large tree above casts shade.
The maple's own branches are so crowded that light cannot get inside.
A building blocks the afternoon sun.
We can help with the first two. We thin the branches of the tree above to let light fall, or we open up the inside of the maple so each branch gets sun. The following autumn, the colour changes.
When a customer tells us their maple's colour has gone dull, the answer is often not in the maple. It is in the tree standing over it.
Prune after the colour is over
A tree in full autumn colour is still working. It is pulling nutrients back from the leaves into its branches and roots.
So cutting branches while the leaves are still coloured is too early. For deciduous trees, the usual time to prune is after the leaves have fallen. With the leaves gone, the shape of the branches is easy to see, and it is easier to decide which ones to remove.
Enjoy the colour to the end, then prune when you sweep up the fallen leaves.
Common questions
Why is my maple's colour worse than last year? The red pigment is made fresh each autumn, so it depends on that year's weather. A cloudy autumn, or small differences between day and night temperatures, give paler colour. If it gets worse year after year, look for a change in the surroundings, such as nearby trees growing and casting more shade.
Why does my ginkgo turn brownish instead of yellow? The yellow has not gone. The leaf is damaged, and brown compounds are showing. Dry weather, strong wind or root damage can weaken the leaves early. If the leaves turn brown all at once before falling, a dry summer is a likely cause.
Should I feed my maple to get better colour? We do not recommend feeding in autumn. Too much nitrogen keeps the leaves green longer and delays the colour. What helps red leaves is light, not fertiliser.
The colour tells you about the tree
Yellow is a colour that was hidden and comes out. Red is a colour made that autumn. Once you know this, a familiar autumn view starts to look a little different.
If your maple looks less bright than last year, look at the light reaching it, not only at the tree.
