Karuizawa is home to more than 1,000 species of plants, and the presence of numerous rare species has attracted the attention of botanical researchers for many years.
Karuizawa is a flat plateau about 1000 m above sea level, surrounded by mountains about 1500 m high, with the 2568-meter Mount Asama rising at its northern end. Thanks to this varied topography, a variety of natural environments exist, including forests, grasslands, and wetlands, each with a diverse vegetation adapted to each environment.
Karuizawa is the northern limit of plants with a Pacific-type climate, where such plants as the Japanese azalea (Rhododendron japonicum) and the Japanese daphne (Rengeshouma) can be found. A group of plants called “continental elements” can also be seen, such as asama furoshiro (Asama furoshiro) and embisenkou (Embisenkou), which are distributed throughout the continent, including eastern Siberia, northeastern China, and the Korean Peninsula, and are isolated in Japan in only a few areas, such as Karuizawa.
The vegetation in Karuizawa was greatly affected by the eruption of Mt. Asama, a volcano. In particular, it is believed that the eruption in 1783 covered almost the entire area of the town with pumice stone, which killed many plants. Most of the plants that can be seen in Karuizawa today were brought in from the surrounding area and grew over the next 200 years.
- ~The primrose, the town flower
- The primrose is designated as the town flower. Primrose is a member of the primrose family, and its beautiful bright pink flowers bloom from May to June. It prefers moist areas on the forest floor or forest edges, and sometimes one can find wonderful clusters of several hundred plants. Unfortunately, however, it has been declining in recent years due to pilfering and other reasons.
■Suggested wildflower walks
- ~The promenade from the old Karuizawa shopping street to the viewing platform
- This is a 2-hour walk from Kyu-Karuizawa to the viewing platform at the Usui Pass. There is a small fishing bridge, and you can listen to the murmuring of the stream as you walk along the path. In spring, violets and catkins can be seen here, and in summer, flowers along the stream can be seen.
- ~Ri Mountain Trail~.
- With an elevation of 1255, it takes about two hours to reach the summit on foot. This course is recommended for observing spring plants such as lilium, primrose, and hitorishizuka.
■Major wildflowers found in spring
Spring comes late on the Karuizawa Plateau at an elevation of 1,000 meters, and wild flowers begin to bloom around mid-April. Temperatures drop 0.6°C for every 100 m rise in elevation, so Karuizawa’s temperatures are about 6°C lower than those in lower temperate regions. However, once the flowers begin to bloom, all the flowers that have been waiting for spring until then will be in full bloom all over the place. In Karuizawa, which is surrounded by forests, plants that can only be found in forests in other regions can often be seen in residential areas, villas, and other familiar places. Until mid-June, when the rainy season begins, a wide variety of wildflowers bloom in turn.
■Flowers found in forests and woodlands
Some spring-blooming plants in forests and woodlands surprisingly complete the entire process from flowering to seed bearing in just one or two months. For example, the azumaichige flower, for example, sprouts in mid-April, blooms within a week or so, produces seeds by the end of May, and by the beginning of June, its leaves turn yellow and wither. There is a reason why Azumaichige are in such a hurry. The reason is that when the trees directly above them spread their leaves from their winter buds, no light reaches the ground and photosynthesis is no longer possible. They finish everything in a great hurry before the leaves of the trees cover their overheads, and then they sleep and live underground
until next spring again. This group of plants that live this kind of life is called early spring plants (spring ephemerals). Common forest and woodland flowers found in Karuizawa include Azumaichige, Eisen-sumire, Hashiridokoro, Nekonome-so, Yama-engosaku, Rurisou, Konronsou, Ruiyou-botan, Chigoyuri, Yama-shakuyaku, and Hitorishizuka.
■Flowers found in grasslands and human settlements
In spring, many flowers can be seen around people’s homes and other familiar places. In parks, on playing fields, around rice paddies and fields, and along riverbanks, a wide variety of colorful wildflowers can be seen. Common wildflowers include the giant dogtooth violet (Ranunculus japonicus), the nazuna (Rana rugosa), the dogtooth violet (Ranunculus japonicus), the kakidoopsis (Ranunculus japonicus), the purple-eyed peony (Ranunculus nigricans), the tachitsubosumire (Vitis vinifera), the kijimushiro (Violetsia violetsifolia), violets, and primroses.
■Major wildflowers found from summer to fall
Most flowers that bloom in summer are found not in dimly lit forests, but in brightly lit areas with sunlight, such as forest edges and meadows. Because sunlight does not reach the ground in the thickly
leafed summer woods, only plants that can grow in dark places can bloom. Therefore, it is recommended to go flower-watching in summer along mountain streams, forest roads, meadows, and highlands. From mid-July, when the rainy season is over, until late August, many summer flowers are in bloom, delighting our eyes.
Many of the flowers that bloom in autumn are found around rice paddies and in grasslands. The best time to visit these open areas is from September to mid-October.
■ Typical summer flowers commonly seen
- ～Flowers found in forests, around woods, and along mountain streams
- To search for wildflowers in summer, it is recommended to walk around forests, woods, and along mountain streams. Look for summer flowers while listening to the cool sound of the stream and the moderate sunlight filtering through the trees. ヤマホタルブクロ、シモツケソウ、シキンカラマツ、クガイソウ、オオバギボウシ、フシグロセンノウ、オタカラコウ、キオンなどが見られる。
On the grasslands and plateaus, you can also see eustoma grandiflora, Japanese iris, Japanese snowdrops, Japanese snowdrops, willow orchids, Siberian lily, and Japanese knotweed.
■ Typical autumn flowers commonly seen
Karuizawa used to have many grasslands, as it was difficult for trees to grow in the area due to the eruption of Mt. Asama in the past. Many of the flowers that bloom in autumn are found in such meadows, making Karuizawa a treasure trove of autumn flowers. In addition, many autumn wildflowers have purple flowers, such as kikyos, gentians, and mountain aconite. One person who used to ride the Kusakaru Electric Railway, which extended from Karuizawa to Kusatsu, said that from the train windows, the kyokyos were in full bloom, as if they were cultivated. In recent years, as trees have grown and grasslands have diminished, such scenes have become rare.
The main autumn flowers include the kyokio, ominae, nokongiku, akinochilinso, yakushisou, gentian, gentian, gentiana, koshogama, yugagiku, white alder, and matsumisou.
