Let’s go acorn-collecting!
Acorns can be collected almost everywhere in Japan, even in the city parks and remnants of the satoyama.
Oaks form a major component of native forests throughout Japan. On the seacoasts, you’ll find the ubame-gashi (Quercus phillyraeoides), while a hardy variety of the mizunara (Q. crispula) can be found high in the subalpine zone, right up to the very edge of the timberline. The kashiwa (Q. dentata) mixes it up with spruce and fir in the subarctic woodlands of Hokkaido while in the south, the Okinawa urajirogashi (Q. miyagii) is a common tree in the subtropical forests of Okinawa Prefecture.
Look for Japanese acorns wherever you see a wood or forest. Try to find some with the cupule (the outer protective covering) still attached, or collect some cupules from the ground as well. Also be sure to collect some typical leaves from the tree, and if possible, to take a picture of the trunk. Japan is home to 15 or 16 species of true oak, plus two species each of tanoak (genus Lithocarpus) and chinkapin (genus Castanospis) that also produce acorns.
Trying to determine an acorn’s species with the acorn and beechnut identification chart below:
There are four basic types; burred, scaled, ringed and sheathed.
The burred acorns, with only three species, all deciduous forest trees, are pretty easy to work with. The kashiwa (Q. dentata) has deep lobes on the leaf, while the two species with lanceolate (long, thin) leaves and sharp spines can be told apart by checking the color on the underside of the leaf, green in the kunugi (Q. acutissima) and with a whitish tint in the abemaki (Q. variabilis).
The sheathed acorns belong to one of two species of chinkapin:
— the sudajii (C. sieboldii) has oval acorns and a deeply furrowed trunk;
— the tsuburajii (C. cuspidata) has rounder acorns and a smooth trunk.
The scaled acorns are a bit more complicated. There are three species with lobed leaves, all deciduous forest trees (look carefully at the size of the leaf and the length of the leaf stalk).
— the mizunara (Q. crispula) — the stalk is either very short or totally lacking;
— the konara (Q. serrata) — has a conspicuously longer stalk. The konara is usually found in lowland forests, and the mizunara higher up on the mountainsides, but there are some areas where their ranges overlap. The nara-gashiwa (Q. aliena) is an uncommon species with a fairly long stalk, but with leaves much larger than the other two species.
— the ubame-gashi is an evergreen coastal species with a scaled acorn. The oval leaves are small, with distinct teeth on the margin.
— the mateba-jii tanoak (L. edulis) also has a scaled acorn. This species grows wild in Kyushu, but is planted widely in parks and along streets, and also in plantations on the Boso and Miura peninsulas. Its acorn is among the largest found here in Japan.
— the shiribuka-gashi (L. glabra)
The ringed acorns, all evergreen forest trees, form by far and away the most difficult group. You have to carefully check the edge of the leaf for teeth or bumps, and also turn the leaf over to inspect the underside for color.
— Only one of these, the aka-gashi (Q. acuta) has entire leaf margins. The rest have varied size and number of teeth, though none of them are lobed like the deciduous species.
— Both the urajiro-gashi (Q. salicina) and Okinawa urajirogashi both show a distinctive white tint on the underside of the leaf, but the latter sports enormous (four centimeters long) acorns more than twice the size of the former.
Other useful facts:
About 500 to 600 species of Oaks, classified in the genus Quercus, may be found worldwide. They are among the most common and familiar trees of temperate zones in the Northern hemisphere. Together with beech, chestnut, tanoak and chinkapin, they form the Fagaceae, or beech family. Both tanoaks and chinkapins, with 300 and 100 species each, also produce acorns, giving a grand total of nearly 1,000 species of acorn trees!
The outstanding characteristic of the beech family is the hard nut, which is found inside a protective covering known as a cupule.