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This year, the autumn color has been truly magnificent in the Kansai region, primarily thanks to the Japanese maple. Every year, these trees are almost guaranteed to deliver wonderful yellow-and-red fall foliage, but this year the sudden drop in temperature in the first few days of November pushed into high gear the mechanisms that control the color pigments in deciduous trees.

There are two chemicals responsible for autumn coloration. Carotenoid pigments produce the yellow and orange colors in leaves, and warm overcast nights favor the dominance of these colors. Meanwhile, anthocyanin pigments cause leaves to turn red, violet and purple, and bright sunny days with clear skies and low night temperatures encourage anthocyanins.

Some trees have a large proportion of one or other of these two pigments, leading to a dominance of either red coloration, if there are more anthocyanins, or yellow coloration if there are more carotenoids. For example, the beautiful fan-shaped icho (maidenhair tree; Ginkgo biloba) turns a lovely golden-yellow before losing its leaves. Its autumn color is always yellow with no trace of red. In Hibiya Park in Tokyo, the oldest tree is a 400-year-old icho known as kubikake icho, which was a sapling in the Momoyama Period (1573-1603). During the construction of the park, this venerable specimen was in the way, and so it was moved 450 meters to its present site, where it is thriving to this day.

Iroha-momiji (Japanese maple; Acer palmatum) is a deciduous tree native to the Korean Peninsula and Japan, except for Hokkaido. Introduced to Europe in 1820, its popularity has since spread far and wide. Although it is classified as a small tree, and rarely grows to more than 8 meters in cultivation, the Japanese maple can reach up to 15 meters in the wild. Every autumn, Kyoto is crowded with sightseers drawn to the autumn color in Arashiyama in the Saga area, or around Engetsu-kyo, a wooden bridge that spans a short valley in the southeast of the city. These areas have been planted with iroha-momiji, which make them famous for their autumn displays.

Leaves of the iroha-momiji are 4-7 cm long and have 5-9 finely toothed, tapered lobes. Leaf color is predominantly red and orange. Oo-momiji is a subspecies of the iroha-momiji (Acer palmatum, ssp. amoenum) that is endemic to Japan and grows all over the country, including Hokkaido. Leaves are lobed like the iroha-momiji, but larger, between 7-12 cm long. Both these maples are frequently planted in gardens and parks and along streets, and are also used in bonsai culture. There are numerous delightful cultivars of these maples. Plant in direct sunlight in a humus-rich, moisture-retentive soil. Japanese maples will grow successfully in containers.

Keep an eye out for the scarlet-to-flame colors of the natsu-tsuta, also known as tsuta (Boston ivy; Parthenocissus tricuspidata). Other common names for this member of the Vitaceae (grape) family include Virginia creeper and Japanese creeper. In fact, the name Boston ivy is misleading: Although this is a popular deciduous climber in Europe and North America, it is native to Japan, the Korean Peninsula and China. A very vigorous climber, it can ascend to 20 meters or more and can be found in forests and climbing over rocks here up to an elevation of 1,200 meters. Its leaves, up to 12 cm long, are trifoliate, and the plant climbs by means of round, padlike suckers on the tendrils. Flowers are insignificant and are followed by small, black-purple berries.

One plant that is rarely sold at garden centers is the sarutori-ibara (cat briar; Smilax china). Commonly used in ikebana, this is also known as China briar and green briar, a name taken from its green stems and bamboo vines. Sarutori-ibara is a deciduous, monocotyledonous climber with leathery, broad, ovate leaves 8 cm long and wide, with three-seven curved, convergent veins. Sinuous, wiry tendrils arise from the leaf stems (petioles), whose undersides are armed with stout thorns. It is from these thorns that the Japanese name is derived: suru-tori-ibara (even monkeys will get pulled down). Despite the bad press this plant gets, it deserves to be planted more often. If you want to stop people trespassing, plant it together with pyracantha (firethorn) to form an impenetrable barrier. Small yellow-green flowers are borne in spring in umbels, with male and female ones on separate plants. Between November and December, beautiful scarlet-colored berries, 9 mm in diameter, ripen in bunches. Also, the fleshy tuberous roots of sarutori-ibara are used medicinally to yield China root, which is taken internally for rheumatoid arthritis, gout, syphilis, skin disorders, enteritis, urinary tract infections, jaundice, skin ulcers and various cancers.

Another red-berried plant — one I became acquainted with when working at the Royal Botanic Gardens in Edinburgh — is omoto (Rohdea japonica), a small but delightful, shade-loving evergreen perennial that is often seen in Japanese tsuboniwa (courtyard gardens). The name omoto means “base” or “foundation” — alluding to the plant’s small size. The genus name commemorates Michael Rohde (1712-1812), a physician from Bremen, Germany. Omoto grows in woodlands in the warmer parts of Honshu and Kyushu, and is also native to southeast China. During the Edo Period (1603-1867), omoto became very popular, and more than 500 cultivars were grown, many with variegated, twisted and curled leaves. Even today, some of these omoto plants are collectors’ items and are very expensive. These cultivars are usually grown in tallish, narrow, black earthenware pots. People who have small gardens can grow the less expensive kinds and get just as much satisfaction.

The plant spreads very slowly by rhizomes. Its dark-green-colored leaves are succulent, long and narrow, 30-50 cm long and 3-5 cm wide. They are leathery with a shiny upper surface. The flowering stems are 10-20 cm long, and 2-3.5 cm-long flower spikes at the tip bear many pale-yellow, 5 mm-wide blooms between May and June. Interestingly, the flowers are pollinated by slugs and snails that feed on the fleshy flowers, which smell of bad bread! Don’t worry, the smell is not overpowering. The fruit is borne as bunches of beautiful, bright-red berries, 8 mm in diameter. This plant will tolerate considerable neglect but, when planted in semishade in a well-drained, humus-rich soil, it responds very well. Propagation is by division of the rhizome in spring. Daily watering is not essential.

I hope you, too, enjoy this year’s great fall show.

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