Summer Solstice 2026

Yesterday June 21, 2026 was this year’s summer solstice.  The summer solstice marks the longest day of the year, providing the maximum amount of sunlight and solar radiation.  The Earth is tilted on its fixed axis by about 23.5 degrees. Because of this, different parts of the planet receive different amounts of sunlight throughout the year as the Earth orbits the sun.  While the solstice is generally referred to as a day, it’s actually an exact moment the sun reaches its northernmost point or alignment, directly overhead at the Tropic of Cancer.  During the weeks following the solstice, the earth and concrete surfaces absorb more heat during the long daytime hours than they can release during the short nights.  This gradual buildup means that the hottest temperatures of the year typically occur delayed, arriving over the next one to two months, in late July and August.

The Tropic of Cancer is an imaginary line of latitude circling the Earth at about 23.5° north of the equator. It spans three continents, passing through areas including Mexico, the Bahamas, the Sahara Desert, India and China.

Also notable is not only the length of the day, but also the height of the sun. During the summer solstice, sunlight hits the ground at a steeper, higher angle, which is part of the reason for the warmer temperatures associated with summer.

If Earth’s axis were not tilted, seasons would effectively cease to exist. There would be no summer or winter solstices, and every location on the planet would experience a nearly identical climate and constant 12-hour days year-round, permanently stuck in an “equinox” state.

It seems that over 20,000 people gathered and welcomed the Sun at Stonehenge on June 21st. According to English Heritage, they witnessed the summer solstice sunrise, marking the Northern Hemisphere’s longest day. It said that the clear weather provided a striking view as the sun rose at 4:24 a.m. BST over the Heel Stone.

Some Common Invasive Weeds in the Floodplains of the Fuji River

Plains coreopsis (Coreopsis tinctoria): https://en.wikipedia.org/wiki/Plains_coreopsis

Floodplains of the Fuji River, Nanbu-cho, Yamanashi, 6/15/2026

Sweet William catchfly (Atocion armeria): https://en.wikipedia.org/wiki/Atocion_armeria; East Asian arrowroot (Pueraria montana var. lobata): https://en.wikipedia.org/wiki/Pueraria_montana_var._lobata; Kudzu in the United States, “The vine that ate the South”: https://en.wikipedia.org/wiki/Kudzu_in_the_United_States

Sweet William catchfly and East Asian arrowroot, or kudzu vine, the floodplains of the Fuji River, Nanbu-cho, Yamanashi, 6/15/2026

Fuji River: https://en.wikipedia.org/wiki/Fuji_River

Fuji River and its riverbanks and floodplains, Nanbu-cho, Yamanashi, 6/15/2026

Roadside Station Tomizawa: https://www.yamanashi-kankou.jp/english/discover/road-station-tomizawa.html; (In Japanese) https://michinoeki-tomizawa.jp/

Burn Swallow (Hirundo rustica): https://en.wikipedia.org/wiki/Barn_swallow

Welcoming and guarding swallows (In use), Roadside Station Tomizawa, Nanbu-cho, Yamanashi, 6/15/2026

The Town of Nanbu: https://en.wikipedia.org/wiki/Nanbu,_Yamanashi; (In Japanese) https://www.town.nanbu.yamanashi.jp/index.html

Utsubuna Station, Minobu Line of Central Japan Railway Company: https://en.wikipedia.org/wiki/Utsubuna_Station

Hydrangea macrophylla Flowers in Utsubuna, Nanbu-cho, Yamanashi

Hydrangea macrophylla is a species of flowering plant in the family Hydrangeaceae, native and endemic to Japan. Hydrangea plants come in colors like red, blue, and purple. The base for these colors is a pigment called anthocyanin. This pigment is naturally red. It turns blue when it reacts with aluminum dissolved from the soil.

Consequently, Hydrangea plants that absorb a lot of aluminum become blue, those that absorb none become red, and those in between become purple. Thus, the color of a hydrangea plant changes based on how much aluminum it absorbs from the soil, which depends on the water’s acidity. Acidic soil helps the plant absorb more aluminum (resulting in blue flowers), while neutral to alkaline soil prevents this absorption (resulting in red or pink flowers). Hydrangea plants with white flowers do not contain anthocyanin pigments, so their color never changes. The chemical reaction inside the plant is like this: the aluminum ions bind with the anthocyanin pigments and this reaction forms a blue complex, causing the plant’s flowers to turn blue instead of their usual red. Under natural conditions, in neutral or alkaline soil, aluminum does not dissolve well, so the plant absorbs very little aluminum, leaving the anthocyanins in their natural red state.

In the Utsubuna region in the town of Nanbu in Yamanashi Prefecture, Japan, there is a park, Utsubuna Park, where about 30,000 hydrangea plants representing about 70 different cultivars are grown across a 2.5-hectare (6.2-acre) site. The town of Nanbu is hosting the 23rd Nanbu Hydrangea Festival at Utsubuna Park from June 12 through June 21, 2026.

Hydrangea macrophylla: https://en.wikipedia.org/wiki/Hydrangea_macrophylla

Hydrangea macrophylla flowers, Utsubuna Park, Nanbu-cho, Yamanashi, 6/15/2026

Hiking to Mount Kenashi, Kawaguchiko-machi, Yamanashi

The Torch Azalea (Rhododendron kaempferi), locally known as Yama-tsutsuji (Mountain Azalea), is the most common wild azalea in Japan. It thrives across Hokkaido, Honshu, Shikoku, and Kyushu and it is known for its vibrant red-orange flowers. Blooming from mid-spring to early summer, it is deeply woven into Japanese culture and nature.

Torch azalea (Rhododendron kaempferi): https://en.wikipedia.org/wiki/Rhododendron_kaempferi; (In Japanese) https://mikawanoyasou.org/data/yamatutuji.htm

A torch Azalea tree, near Mount Kenashi, Kawaguchiko-machi, Yamanashi, 6/13, 2026

Kenashiyama, Mount Kenashi (litterily meams Hairless Mountain in Japanese), is located in the Misaka Mountains north of Mount Fuji standing right between Lake Sai and Lake Kawaguchi. Its elevation is 1,500 meters (4,921 feet). The majestic figure of Mount Fuji stretches its base to the horizon directly in front of you with Lake Sai to the right and Lake Kawaguchi to the left, creating a magnificent composition of a sacred mountain.

Mount Kenashi: https://yamanashi–hiking100-jp.translate.goog/course/detail/2?_x_tr_sl=ja&_x_tr_tl=en&_x_tr_hl=en

Mount Fuji views from the peak of Mount Kenashi looking down Lake Sai to the right and Lake Kawaguchi to the left, Mount Kenashi, Kawaguchiko-machi, Yamanashi, 6/13, 2026

Some Riverbank Weeds, Arakawa River, Kofu, Yamanashi

Bushkiller, Japanese bindweed, annual fleabane and Carolina horsenettle, these plants are common weeds found along riverbanks in Japan. Some are native to Japan, while others are invasive plants brought from overseas. Each has unique characteristics and poses different levels of threat to the local ecosystem.

Bushkiller, Arakawa River, Kofu-shi, Yamanashi, 6/11/2026

Bushkiller (Causonis japonica): https://en.wikipedia.org/wiki/Causonis_japonica; (In Japanese) https://mikawanoyasou.org/data/yabugarasi.htm

Japanese bindweed, Arakawa River, Kofu-shi, Yamanashi, 6/11/2026

Japanese bindweed (Calystegia pubescens): https://en.wikipedia.org/wiki/Calystegia_pubescens; (In Japanese) https://mikawanoyasou.org/data/hirugao.htm

Annual fleabane, Arakawa River, Kofu-shi, Yamanashi, 6/11/2026

Annual fleabane (Erigeron annuus): https://en.wikipedia.org/wiki/Erigeron_annuus; (In Japanese) https://mikawanoyasou.org/data/himejyoon.htm

Carolina horsenettle, Arakawa River, Kofu-shi, Yamanashi, 6/11/2026

Carolina horsenettle (Solanum carolinense): https://en.wikipedia.org/wiki/Solanum_carolinense; (In Japanese) https://mikawanoyasou.org/data/warunasubi.htm

A Wine Tasting Tour II

A wine tasting tour for an American man was conducted on June 10, 2026. Six wineries Grace Winery, Lumiere Winery, Marufuji Winery, Haramono Winery, Manns Wines Katsunuma Winery, and Shirayuri Winery were visited.

  1. Grace Winery: https://www.grace-wine.com/en/
  2. Lumiere Winery: https://www.lumiere.jp/en
  3. Marufuji Winery: https://www.rubaiyat.jp/en/
  4. Haramo Winery: https://www.haramo.com/index.html
  5. Manns Wines Katsunuma Winery: https://mannswines.com/
  6. Shirayuri Winery: https://shirayuriwine.com/

Stone samples: granite from Hishiyama Vineyard and conglomerate from Toriibira Vineyard for Grace Koshu Hishiyama Vineyard and Grace Koshu Toriibira Vineyard wine

Grace Winery, Katsunuma-cho, Yamanashi, 6/10/2026

Grapevines

Lumiere Winery, Katsunuma-cho, Yamanashi, 6/10/2026

Grapevines, Lumiere Winery, Katsunuma-cho, Yamanashi, 6/10/2026

Marufuji Winery

Katsunuma-cho, Yamanashi, 6/10/2026

Haramo Wine and grapevines, Haramo Winery, Katsunuma-cho, Yamanashi, 6/10/2026

Hydrangea Blooming and the Start of the Rainy Season

The Japan Meteorological Agency announced the start of the rainy season in the Kanto-Koshin and Tokai regions on June 7, 2026. Hydrangea flowers, known as ajisai in Japanese, bloom perfectly in time with tsuyu, Japan’s rainy season. https://www3.nhk.or.jp/nhkworld/en/news/20260607_11/

Koin Temple, located in the Shimosekisuiji-cho area in the city of Kofu in Yamanashi Prefecture, Japan, belongs to the Soto Zen school in Japanese Buddhism. Koin Temple is a hidden gem famous for its stunning display of over 1,000 blooming hydrangeas. Every June, the temple’s quiet mountain paths and historic gates come alive with vibrant colors, making it a beloved local spot during the rainy season.

Soto-shu (Soto Zen): https://en.wikipedia.org/wiki/S%C5%8Dt%C5%8D; https://www.sotozen.com/eng/about/index.html

Koin Temple, the Soto Zen school

Shimosekisuiji-cho, Kofu-shi, Yamanashi, 6/09/2026

Koinji, Shimosekisuiji-cho, Kofu-shi, Yamanashi, 6/09/2026

Bigleaf hydrangea (Hydrangea macrophylla): https://en.wikipedia.org/wiki/Hydrangea_macrophylla

Bigleaf hydrangea, Koinji, Shimosekisuiji-cho, Kofu-shi, Yamanashi, 6/08/2026

Hydrangea macrophylla cv. ‘Uzuazisai’: (In Japanese) https://www.kobe-park.or.jp/cgi-bin/rikyu/zukan/index.cgi?file=zukan&mode=detail&select=1302349118; https://kawasakimidori.main.jp/webzukan/ajisai_p2.html#uzu

Hydrangea macrophylla cv. ‘Uzuazisai’, Koinji, Shimosekisuiji-cho, Kofu-shi, Yamanashi, 6/08/2026

Hydrangea macrophylla cv. ‘Shirotemari‘: https://www.kazahayanosato.com/shirotemari/

Hydrangea macrophylla cv. ‘Shirotemari‘, Koinji, Shimosekisuiji-cho, Kofu-shi, Yamanashi, 6/08/2026

(In Japanese) https://green.sagamiharashi-machimidori.or.jp/%E7%B7%91%E5%8C%96%E6%84%8F%E8%AD%98%E3%81%AE%E6%99%AE%E5%8F%8A%E5%95%93%E7%99%BA/%E3%82%A2%E3%82%B8%E3%82%B5%E3%82%A4%E5%9B%B3%E9%91%91

Picking Mulberries in a Farm in Kai-shi, Yamanashi

Tomi Farm located in the city of Kai in Yamanashi Prefecture, Jaspan, is well known for its seasonal mulberry-picking experience. The farm makes use of the surviving mulberry fields in the region, a nod to the area’s once-thriving silk-farming industry. The mulberry-picking event this year was held during May 27 through June 7.

Silkworm farming (sericulture) and its related silk-reeling industry were a massive part of Yamanashi Prefecture’s history and economic success. The mountainous terrain and favorable climate made it an ideal environment to grow mulberry trees, whose leaves are the primary food source for silkworms.

Mulberry (Morus): https://en.wikipedia.org/wiki/Morus_(plant)

Mulberries, Tomi Farm, Kai-shi, Yamanashi, 6/17/2027

Mulberry trees, Tomi Farm, Kai-shi, Yamanashi, 6/17/2027

Let’s Eradicate an Invasive Species Lanceleaf Coreopsis

Lanceleaf coreopsis (Coreopsis lanceolata): https://en.wikipedia.org/wiki/Coreopsis_lanceolata

Arakawa River, Kofu-shi, Yamanashi, 5/15/2022

Lanceleaf coreopsis (Coreopsis lanceolata), locally known as Okinkeigiku, is troublesome in Yamanashi and all over Japan because of its extreme hardiness and aggressive reproductive traits. Originally introduced for ornamental and greening purposes from North America, Coreopsis lanceolata outcompetes native vegetation and harms the region’s biodiversity. Coreopsis lanceolata is legally designated as an Invasive Alien Species in Japan and the cultivation, transportation, and sale of the plant are strictly prohibited.

https://www.nilim.go.jp/english/annual/annual2011/3-4-16.pdf; https://www.nies.go.jp/biodiversity/invasive/DB/detail/80490e.html; https://www.pref.yamanashi.jp.e.aao.hp.transer.com/shizen/gairaiseibutu/ookinkeigiku.html

The plant poses a significant threat to Yamanashi’s unique ecosystems for several concrete reasons:

  • Aggressive Soil Competition: Coreopsis lanceolata grows a dense foliar canopy that blocks vital understory light. This shades out and displaces native grasses and endemic riparian plants.
  • High Reproductive Capacity: The plant produces thousands of seeds that can survive in the soil for years.
  • Tough, Perennial Constitution: It spreads rapidly through both seeds and rhizomes. Even after rigorous cutting or mowing, the plant recovers quickly and easily.
  • Disruptive to Infrastructure and Scenery: It frequently invades roadsides, riverbeds, and hiking trails, making local conservation efforts necessary to protect indigenous species from being choked out.

Because the plant has been integrated into the local pollinator community (like Halictidae, sweet bees), its seeds are easily and consistently propagated.

Several municipalities and volunteer groups across Japan are frequently forced to organize massive, labor-intensive eradication events to dispose of Coreopsis lanceolata properly.

Some examples are as follows:

TOGO SEISAKUSYO CORPORATION; We carried out eradication work on the invasive species “Coreopsis lanceolata”: https://www.togoh.co.jp/en/news/news-482

Shizuoka City conducted a simultaneous eradication campaign for Coreopsis lanceolata across eight locations to protect native plant species from this highly invasive alien species on May 26, 2026.

As one of the Corporate Social Responsibility activities, Sango Co., Ltd., based in the city of Miyoshi in Aichi Prefecture, has been involving in eradication of Coreopsis lanceolata since 2016. Sango Co., Ltd.: https://sango.jp/en/

Protect Our Island from Invasive Species! Call for Volunteers to Weed Out Lance-leaved Tickseed: https://www.oki-geopark.jp/en/news/4806/

In Yamanashi Prefecture, the cities of Nirasaki, Fuefuki, and Fujiyoshida and the towns of Hayakawa and Fujikawaguchiko and also the government of Yamanashi Prefecture have organized eradication events to dispose of Coreopsis lanceolata properly.

Also, please read the article on Invasive Plants: Lance-leaved tickseed and Kudzu: https://etsuo.tokyo/2022/06/.