The 2018 summer growing season has come to an end with a hard freeze a few days ago. But, before winter arrived, my deciduous bonsai decided to put on a show and I’d like to share thier beauty with you.

The spectacle of green foliage turning rich red, yellow and orange in autumn happens when trees have taken all the food they can from the foliage which is filled with chlorophyll, the molecule that absorbs energy from the sun and gives leaves their green coloring. When the length of daylight and temperatures decreases leaves cease to manufacture food and when the green colored chlorophyll is broken down other colors are revealed.

Usually each species has a common autumn coloring. Maidenhair trees, or Ginkgo and Birch normally become bright yellow in autumn before leaf drop. Japanese maples often turn brilliant red, sometimes orange and even yellow foliage. I’ve even had Chinese elm leaves change to pink before dropping to reveal the quiet beauty of small fine twigs and grey bark. Japanese, European and American beech leaves usually become yellow in autumn rather than orange or red. Of course there are physiological reasons for these leaf color changes, which plant scientists have studied and can better explain.

However, I’m a bonsai artist and educator, and although I’ve earned two ornamental horticultural degrees this topic does not really interest me because what goes on inside the leaf can’t be changed. However, what I am interested in is to understand how to enhance autumn coloring.

Although each species has a “normal” autumn coloring, each year presents a different show of color depending on the daylight, temperature, water, fertilizer and trimming techniques. All of these elements contribute to the autumn foliage colors. I’ve had Trident maple bonsai turn rich red one year, orange the next year, clear yellow another year and sometimes all three colors in one leaf.

If deciduous bonsai are defoliated during the summer to reduce leaf size and increase fine twigs they often present richer autumn colors because of the chemical balance inside the leaves. It seems that the younger foliage change too more intense colors than bonsai with only older foliage which were not defoliated.

It seems that if the summer weather is hot and wet the foliage does not become brilliant in autumn. If the bonsai tend to dry out during late summer autumn coloring will be better than normal. Perhaps the slight stress stimulates rich coloring.

 

Fertilizing bonsai also contributes to the autumn foliage color change. If fertilizer applications stop in August or September the autumn colors begin sooner than if fertilizer is given in September into October. I do not change my fertilizer schedule during the year. Beginning in May and continuing to September, sometimes October, I use a mixture of high Nitrogen fertilizers throughout the growing season.
The addition of Nitrogen will be beneficial to the tree in spring. I do not reduce the Nitrogen levels as the growing season progresses. Most growers do not recommended this, because they say the addition of Nitrogen fertilizer will encourage late new growth which might be damaged by cold weather because they don’t have time to mature. This is not true if you have regularly fertilized with high Nitrogen fertilizer throughout the growing season. New growth will not be encouraged. However, look at my bonsai. I must be doing something right because my bonsai always reward me with a colorful show before leaf drop.

Kashima Japanese maple. The outer layer of leaves were gently plucked to reveal an undamaged fresh foliage.

During late summer some deciduous leaves show a discoloration or leaf burn around the edges because the leaves are thinner towards the tips. We often let them remain until September or October then gently pluck an entire layer of the damaged foliage revealing an older crop of foliage which has not been damaged. These new leaves become exposed to the sunlight and change color. As the growing season ends they put on a colorful showing. These bonsai are often put on turntables and rotated a couple of times a week so both sides of the bonsai can receive an even amount of sun. If the bonsai are not rotated the coloring of each side often differs. Bonsai kept in the shade tend to change color later than those in the full sun.

2015

2016

November 4, 2018

November 8, 2018

This past summer we kept a multiple trunk Japanese maple in an area which received only late afternoon sun and the foliage did not burn. In late September it was moved into a sunnier location and rotated. This year this Japanese maple bonsai became light yellow, then a few days later a rich yellow. Two years ago the same bonsai turned light orange and the year before that it was dark orange. When the trees begin to change color it comes quickly and changes during the day, hour by hour.

European Beech

Usually Maidenhair trees, or Ginkgo, become yellow then suddenly all the foliage drops at one time. This year my Maidenhair tree bonsai failed to put on a show, while the garden tree changed to its normal rich yellow.

Shishigashira Japanese Maple

It takes considerable time to photograph deciduous bonsai to capture their beauty. I was waiting for my Full moon maple to change color. It almost peaked but the weather changed and it rained. The leaves were not knocked off, but the trunk became wet and dark. Its best to photograph bonsai when they are dry so details are revealed. This bonsai was peaking and the bark was wet. We tried paper towels and even a fan, but it did not help to dry out the bark, especially near the surface root region next to the moss. If you bring a bonsai changing color indoors to protect it from rain and wind you take a chance of drying out the leaves. Its best to keep the bonsai outdoors, out of the wind and away from rain. Low humidity is not good for maintaining colorful foliage. The leaves become a dull color, crispy and drop.

Full Moon Maple, May 2018.

November 1, 2018.

November 3, 2018.

November 4, 2018.

Weather changes and the brief magnificent autumn colors can quickly change. A few days after these colorful photos were taken it snowed about an inch. Good thing we photographed the bonsai last weekend not this weekend.

Japanese Zelkova

After the bonsai present their beautiful foliage changes we remove the old leaves to reveal the fine twigs and bark textures. Usually my bonsai remain outdoors until they get a light dusting of snow because the gritty snow cleans the bark as it melts. Then my bonsai are protected for the long cold winter.

Shishigashira Japanese Maple November 4, 2018.

Shishigashira Japanese Maple November 8, 2018.

Euonymus sieboldiana

However, this year I have a different situation because of my upcoming Autumn Bonsai Tour to Japan during the Thanksgiving holiday. The Nippon Bonsai Association did not consider the American Thanksgiving holiday when they scheduled the Nippon Bonsai Taikan Exhibition. It is held during a long Japanese holiday weekend so visitors to Kyoto can enjoy both the colorful gardens and the bonsai exhibition. Two days after returning from Japan we must leave for the Winter Silhouette Bonsai Expo in North Carolina. So, it was necessary for me to begin protecting my bonsai early.

November 9, 2018

Well, the bonsai did get a dusting of snow beforehand. A few weeks ago we began protecting the nursery stock and sales bonsai, keeping my better bonsai outside as long as possible. Usually the bonsai remain outdoors until Thanksgiving or early December, depending on the season. Personally, I hate cold weather and snow and tend to go dormant at 70F. So, I’m off in a few days to show friends the Japanese bonsai world where it will be warmer than it is in Rochester, New York.