There was another article about sacred forests in the January 24th issue of Jinja Shinpō, and this one was also by Prof. Watanabë. It is not about sacred forests per se, but rather about the use of plants and trees in Shinto matsuri.
This article is a problem to write about, because it refers to all the specific species of plants that are used in matsuri at different jinja and in different regions of Japan, and it does so by their Japanese names. I recognise most of these in Japanese, but not all, and while I could look them up and find English names, those would mean nothing to most of my readers. In any case, knowing exactly which plant it is would not add much to most people’s understanding. So, I am not going to bother with massive lists of names.
Plants are widely used in Shinto matsuri. The most prominent is sakaki, the broad-leaf evergreen that is placed on a kamidana or displayed in prayer halls, and used to make tamagushi. This is normally identified with a particular species, Cleyera japonica, but, as Prof. Watanabë points out, that species is not found across the whole of Japan. I live near the northern end of its range. Thus, jinja outside that range, and even some within, have traditionally used other species for tamagushi, or to decorate the sanctuary. These are always woody, evergreen plants, but they seem to cover a wide range within that — the article mentions six other species, and that is unlikely to be exhaustive.
There is a reason, beyond the practical, for this diversity. “Sakaki” was not originally the name of a particular species of plant. Instead, it was the name for plants that marked the boundary between the sacred and the secular. Indeed, one of the proposed etymologies for “sakaki” is “sakai no ki”, which means “border tree”. Thus, jinja would use a suitable tree that grew in the local area.
Nowadays, you can buy Chinese-grown sakaki in most supermarkets, or Japanese-grown sakaki for about twice the price. A lot of people use artificial plastic sakaki on their kamidana, and even a lot of jinja use them for the interior decorations (although not, in my experience, for tamagushi). This is because you do not have to replace plastic sakaki anything like as often as real ones, and they do not wither and die in the summer. Prof. Watanabë thinks that is a shame, and wants to encourage jinja to use branches from a tree that they can grow in the precincts. I have to say that I am inclined to agree with him.
Other plants are also used, in different ways, in a wide range of matsuri. The account of Amë-no-Uzumë’s dance in the Kojiki and Nihonshoki has her wearing a crown and sash made of some variety of ivy, and carrying bamboo grass in her hands. This is still seen in some local, traditional sacred dance, with plants depending on the jinja. Further, at some jinja, all the participants in particular matsuri wear sashes made of a particular kind of ivy.
Similarly, some jinja have a tradition that the people participating in a particular matsuri decorate their headgear with a particular plant. By far the most famous example of this is the Kamo Matsuri at the two Kamo Jinja in Kyoto, where people wear aoi leaves. The association here is so strong that the matsuri is often called the Aoi Matsuri.
The connection between Shinto matsuri and plants is very strong, but not something that is formally emphasised in modern regulations. At some jinja, however, a plant has great symbolic importance as part of the vestments for a matsuri.