Daikonshima Island is a scenic island floating in Lake Nakaumi in eastern Shimane Prefecture. Administratively part of Matsue City, the island measures approximately 3.3 kilometers from east to west and 2.2 kilometers from north to south, with an area of about 5.15 square kilometers and a coastline of roughly 12 kilometers.
Although surrounded by the calm waters of a brackish lake, Daikonshima has a fascinating volcanic origin. The island was formed by volcanic activity approximately 190,000 years ago, together with neighboring Ejima Island. Today, it is best known as an island of peonies, with spectacular flowers covering its gardens in spring.
The opening of Ejima Ohashi Bridge in 2004 greatly improved access from the direction of Sakaiminato in Tottori Prefecture, making Daikonshima an easy destination to visit by car. A drive across the bridge and along the island offers beautiful views of the surrounding lake and sky.
Daikonshima was formed during the Middle Pleistocene, when volcanic eruptions occurred approximately 190,000 years ago. At the center of the island stands Mount Otsuka, a scoria cone rising about 42 meters above sea level and forming the highest point on the island.
The lava produced by the eruptions was basaltic and relatively low in viscosity. As a result, the island developed gently sloping terrain rather than steep volcanic mountains. At the time of its formation, the Earth was in an ice age and sea levels were considerably lower than today. The surrounding area is thought to have been connected to the mainland, giving the region a geological history quite different from its present appearance.
Small islands such as Kijima, Tsugishima, and Watashima are scattered around the area, adding to the distinctive scenery of Lake Nakaumi.
One of Daikonshima’s most remarkable geological features is its network of lava tunnels. These underground passages were formed when the surface of a lava flow cooled and hardened while molten lava continued to flow beneath it.
Yukidō Cave is designated as a National Special Natural Monument, while Ryūkē Cave is designated as a National Natural Monument. Yukidō Cave is currently closed to visitors, while Ryūkē Cave may be visited with advance arrangements.
These caves are also scientifically valuable because they provide a habitat for the Iwata blind ground beetle, a species endemic to Daikonshima. The island’s volcanic landforms and underground environments are recognized as important geological sites within the wider Japanese Geopark area.
Despite being surrounded by brackish water, Daikonshima has abundant underground freshwater. The island’s permeable volcanic rock allows groundwater to accumulate in what is known as a freshwater lens—a layer of freshwater that forms above denser saltwater underground.
This natural water supply has played an important role in supporting agriculture and everyday life on the island. During the severe drought that affected the San’in region in 1939, Daikonshima was notably spared serious water shortages thanks to its abundant groundwater.
In the Namiiri district in the southern part of the island, clear spring water emerges through gaps in the volcanic rock. The spring is recognized as one of Shimane Prefecture’s Selected Famous Waters, demonstrating how the island’s volcanic origins continue to influence life today.
Daikonshima is one of Japan’s leading centers of peony cultivation and is particularly famous for its exceptionally large-scale production. The island is said to account for more than 80 percent of Japan’s domestic peony seedling production, with approximately two million plants shipped each year.
The history of peony cultivation on the island dates back about 300 years. According to local tradition, the first peonies were planted at Zenryūji Temple in the Namiiri district. Cultivation gradually expanded, and varieties were improved after the Meiji period.
Today, more than 300 varieties are cultivated on the island, creating an extraordinary diversity of colors, shapes, and flower forms.
The main flowering season is from late April to early May. During the Golden Week holiday period, the Daikonshima Peony Festival brings the island to life, with peony gardens filled with brilliant flowers and visitors enjoying the spectacular seasonal scenery.
Daikonshima is home to numerous peony gardens and cultivation facilities, including Yushien Garden, Ejima Peony Garden, Chinese Peony Garden, Daikonshima Honjin, and Daikonshima Peony and Tree Peony Garden. Visitors can experience both traditional Japanese varieties and Chinese peonies introduced through horticultural exchange with Shandong Province in China.
One of the island’s best-known attractions is Yushien Garden, a traditional Japanese strolling garden covering approximately 33,000 square meters. Its ponds, streams, bridges, rocks, and seasonal plants create a landscape designed to be enjoyed while walking through the garden.
Peonies are one of Yushien’s greatest attractions. At the indoor Peony Pavilion, visitors can admire peonies throughout the year, even outside the natural flowering season.
The garden also offers seasonal experiences beyond spring. Autumn brings colorful foliage and nighttime illumination, while winter features special art events. The changing scenery makes Yushien a destination that can be enjoyed in different ways throughout the year.
Long before peony cultivation became the island’s signature industry, Daikonshima was known for growing Unshu ginseng, also known as Japanese ginseng or Panax ginseng. Cultivation began during the middle of the Edo period as an agricultural enterprise promoted by the Matsue Domain, becoming an important source of revenue for the domain.
The crop requires extraordinary patience. It takes approximately six years from planting to harvest, and the same field cannot be used continuously because the plant cannot be grown repeatedly in the same soil. These demanding growing conditions have contributed to the rarity and value of Daikonshima’s ginseng.
Along with Nagano and Fukushima prefectures, the area has traditionally been regarded as one of Japan’s major production regions. Although the cultivated area has declined in recent years due in part to an aging farming population, Unshu ginseng remains an important part of Daikonshima’s agricultural heritage.
Daikonshima is also a place where visitors can encounter the long history of the Izumo region. Ancient records in the Izumo no Kuni Fudoki, a geographical and cultural record compiled in the Nara period, contain a tradition that the island was once known as Takoshima. The present name is thought to have developed through changes in pronunciation and naming over time.
Historic shrines and Buddhist temples can be found throughout the island, reflecting the religious traditions and everyday life that developed here over the centuries. Exploring these quieter sites provides a different perspective on Daikonshima beyond its famous gardens and flowers.
Daikonshima is also associated with Dr. Hajime Nakamura, an internationally renowned scholar of Eastern philosophy. The Nakamura Hajime Memorial Museum introduces his life and academic achievements and displays part of his extensive personal library of approximately 34,000 books.
The museum adds an intellectual and cultural dimension to an island better known for its flowers and agricultural traditions.
The island’s name is pronounced both Daikonshima and Daikonjima. Official documents and broadcasting commonly use the pronunciation “Daikonshima,” although the “-jima” pronunciation has also been used historically.
Daikonshima is connected to the mainland and the Tottori Prefecture side by roads and bridges, making it convenient to explore by car. The Ejima Ohashi Bridge, in particular, has become a recognizable part of the area’s scenery.
Driving across the bridges with Lake Nakaumi stretching on either side is itself part of the experience. The combination of open water, volcanic landscapes, rural fields, and distant mountains creates a peaceful journey through one of the distinctive landscapes of eastern Shimane.
Daikonshima is an island where volcanic geology, abundant groundwater, agriculture, flowers, history, and local culture have developed together over thousands of years.
Its gentle landscape was created by volcanic activity approximately 190,000 years ago. Its underground freshwater resources helped sustain agriculture, while centuries of cultivation gave rise to the island’s famous peonies and Unshu ginseng.
Spring is the most spectacular season, when the island is filled with magnificent peonies. Summer brings lush green fields and calm lakeside scenery, while autumn and winter offer a quieter atmosphere and peaceful views across Lake Nakaumi.
For overseas visitors, Daikonshima offers an opportunity to experience a side of Japan that goes beyond the country’s famous cities and temples. A visit here reveals how nature, traditional agriculture, gardens, and local history can become part of one island’s cultural identity.
When exploring the Matsue and Lake Nakaumi area, consider adding Daikonshima to your itinerary and discover the fascinating story of this small volcanic island surrounded by water.