The Japanese archipelago is home to five or six species of pine tree. The number is debated because among these species are geographical subspecies, varieties, ecotypes and "physiological races," the last expression referring to pine varieties that look similar, but are physiologically different, as seen in such points as the chemical composition of their essential oils.

Sculpted umbrella trees grafted onto black-pine stocks in Shinjuku Gyoen

Pines belong to the genus Pinus (matsu-zoku) in the Pinaceae family (matsu-ka). Worldwide there are reckoned to be 93 species of pine, all (except one species, Pinus merkusii in the Philippines and Sumatra) naturally distributed only in the Northern Hemisphere. An interesting point is that although pine species are relatively few, there are enormous numbers of individual trees.

The Japanese stone pine or dwarf Siberian pine (Pinus pumila), for example, covers millions of square kilometers in northeastern Asia, including parts of Japan. In Japan this shrubby tree is called hai-matsu and grows only in alpine areas on high mountains in Honshu and at a lower elevation in Hokkaido. These mountains are exposed to very strong winds and heavy snowfall, and yet the hai-matsu survives.

The red umbrella pine trees in Shiga are endangered by nematodes.

Pine trees are pioneer plants that quickly colonize vacant land. They have evolved over millions of years and developed xerophytic structures to help survive in arid or highly exposed places and in poor soils. The casual observer can easily see how the leaves have adapted to their tough environment: They are needlelike, long and rigid with a small surface area, sunken stomata (tiny "breathing" holes found on the underside of leaves, which allow gases to pass in and out), a thick cuticle and a waxy bloom covering the leaf surface, both helping to prevent excess moisture loss.

Pines are evergreen monoecious trees (i.e., male and female flowers are carried on the same tree). Male cones are short, catkinlike cylinders and contain many fertile sacs, each with two pollen sacs. In each spore sac (known as microsporangia) develop pollen mother cells, which undergo chromosome reduction division. Each of these pollen mother cells produces four microspores in which the 24 chromosomes of the parent tree are reduced by half. These microspores develop into pollen grains.

Each pollen grain has two air sacs, which make the pollen buoyant and aid in wind dispersal. Female cones have tiny bract scales, and at the base or axis are the cone scales (ovuliferous or fertile), each with two ovules on the underside. Female cones take between two and three years to mature following the arrival of the pollen from the male flowers.

Pines are all pollinated by wind. Pollen is produced in great quantities and released in a great sulfur-yellow cloud. Only a very tiny amount reaches the female flowers. Nearly all pine seeds are winged, to help them disperse when mature.

The pines that inhabit the Japanese archipelago include Japanese stone pine, mentioned above, which bears its needles in groups of five. In Hokkaido it is used to make bonsai.

The Japanese white pine (goyo-matsu, P. parviflora) is a tall tree, growing up to 35 meters. Like P. pumila, its needles are in groups of five and are a blue-green color. Japanese white pines are often used for bonsai or as garden trees. The timber is used for construction and civil engineering.

The Korean pine (chosen-matsu, P. korainensis) is so called because of its abundance on the Korean Peninsula. In Japan it is mainly confined to the high mountains of central Honshu. It too grows up to 35 meters and, like the two previous species, its needles are grouped in fives. The seeds are edible and are harvested in some areas for food.

Yaku-tane-matsu (P. armandi amamiana) is a rare pine from Yakushima and Tanegashima. Again, the needles are in fives. Another southerner is the Okinawa pine (Ryukyu-matsu, P. luchuensis), found only on the islands of Okinawa Prefecture.

By far the most popular and well-known pine here is the Japanese black pine (kuro-matsu, P. thunbergii). Its leaves are in pairs and each leaf is dark green and slightly twisted. The Japanese black pine grows naturally along the rocky coast and on sandy seashores. The trunk is dark brown, almost black, hence the name.

The Japanese red pine (aka-matsu, P. densiflora) grows throughout Japan, except in Hokkaido. Its leaves are in pairs, and the trunk is orange-red and very attractive. In the Hiramatsu district of Shiga Prefecture's town of Kosei, there is an unusual natural variety of the Japanese red pine. Known in Japanese as utsukushi-matsu, literally, "beautiful pine," it is called Japanese umbrella pine in English. The utsukushi-matsu grows naturally on southeastern slopes of Bisho-yama at 230 meters above sea level. It grows 7-10 meters tall. From just above the surface of the ground, the trunk divides into a number of thick stems and the head is rounded, hence the English name.

This pine grows alongside normal Japanese red pines. In 1998 there were estimated to be 230 trees in the grove in Kosei, which has been known to travelers for hundreds of years and was mentioned in a list of places to see en route to Ise Shrine in Mie Prefecture. It was also listed as a meisho (famous site) along the old Tokaido Highway.

The botanical name for the umbrella pine is Pinus densiflora umbraculifera, and the natural grove in Hiramatsu is a national monument. Unfortunately, this is a national monument with a major problem! Many readers will be aware of matsukui-mushi, which is killing huge numbers of Japanese red pines. A species of long-horned beetle, matsu-no-madara-kamikiri (Monochamus alternatus) carries on its body a nematode known in Japanese as matsu-no-zaisenchu, or more commonly as matsukui-mushi.

When I visited Kosei in January there were many dying trees. Although chemical pesticides are used, they have not stopped the blight.

The nematode is the killer, but it also believed that other factors have a major influence. One is airborne pollution from industrial plants and expressways in built-up areas. Long hot summers help the spread of the long-horned beetle and the nematode. Trees weakened by prolonged exposure to air pollution are easy targets for the insect.

Long-horned beetles have not suddenly appeared out of nowhere; weak pine trees helped them increase their numbers. In Kansai and along the Seto Inland Sea red pines have been wiped out in huge numbers. The Kanto region is also affected, but so far not as badly as western Japan.

Apart from the natural grove in Shiga, a cultivated form of the umbrella pine can be seen in Shinjuku Gyoen in Tokyo. The park's trees have magnificent orange-red trunks -- but a close look at the base of the trees will reveal a different pine. These umbrella pines were grafted onto kuro-matsu!