Sun Moon Lake black tea is Taiwan's most famous red tea: a smooth, naturally sweet black tea grown in the misty lake basin of Yuchi, in Nantou County at the center of the island. What makes it unmistakable is the aroma of its flagship cultivar, Ruby #18 — a cool whisper of mint and cinnamon that rises off the cup before you have taken a sip. That single scent, bred into a single plant, is the whole story of this origin.
What is Sun Moon Lake black tea?
Sun Moon Lake black tea is a fully oxidized Taiwan black tea grown around Sun Moon Lake (Ri Yue Tan), the largest natural lake on the island. A quick vocabulary note that trips people up: "black tea" in English and "red tea" (hong cha) in Chinese are the same fully oxidized style — named in the West for the dark leaf, in East Asia for the red-amber liquor in the cup. For how oxidation turns a green leaf dark and where this style sits in the wider family, see what is black tea; here the point is simply that this is a red tea, and an unusually distinctive one.
Almost all of it is made the orthodox way — whole leaves rolled and oxidized rather than machine-chopped — and most of the leaf that carries the region's name today is a single modern cultivar: Ruby #18, sold interchangeably as Hong Yu, Red Jade and TTES No. 18. That one plant, and the mint-and-cinnamon note it produces naturally, is the reason a lake in central Taiwan became a black-tea name known far beyond the island.
Where it grows, and why the lake matters
Sun Moon Lake sits at roughly 750 m (about 2,450 ft) in the mountains of central Taiwan, and the tea gardens ring it and climb the surrounding slopes to somewhere around 600–1,000 m. That is modest by the standards of Taiwan's famous high-mountain oolongs, and it is meant to be: this is a warm, humid, low-cloud basin rather than a cold peak, and the plant behind the region — a large-leaf assamica — wants exactly that kind of heat.
The land does three things for the cup. The lake and the ridges around it trap moisture, so the gardens spend much of the year under mist and soft, filtered light, which slows the leaf and rounds out its sweetness. The basin's warmth and long growing season suit the broad, heat-loving assamica leaf that gives the tea its malty body. And the deep, iron-rich red soil of the hills is a genuinely good match for this style. It is no accident: when planters first looked for somewhere on the island to grow large-leaf black tea in the early twentieth century, they picked this basin precisely because its warm, misty climate resembled the great assamica growing region of Assam.
Ruby #18: the cultivar that owns the mint-and-cinnamon note
The one thing to remember about this origin is its plant. Ruby #18 — officially TTES No. 18, and known by the poetic name Hong Yu, meaning "red jade" — is a bred cultivar, not a wild or ancient variety. It was created by Taiwan's Tea Research and Extension Station by crossing two very different parents: a Burmese large-leaf assamica, which brings body, malt and a deep red liquor, and a native wild Taiwan mountain tea (Camellia sinensis var. formosensis), an indigenous plant that has grown on the island for far longer than any cultivated garden. From that native parent comes the signature: a natural, cooling menthol-and-cinnamon aroma that no other mainstream black-tea cultivar produces on its own.
The breeding was slow, patient work that ran across the middle of the twentieth century, and the cultivar was only officially registered and released in 1999. The name Hong Yu, "red jade," was chosen for the clear, gem-like red of the brewed tea. So when a tin says Ruby 18 tea, Hong Yu tea or Red Jade tea, it is naming the same plant — the flagship of Sun Moon Lake and the reason the region has a story worth telling.
A colonial project, a long decline, and a revival
Large-leaf black tea did not grow itself here. During the Japanese colonial administration of Taiwan, growers went looking for a way to make export black tea to rival the great assamica estates elsewhere, and in the 1920s and 1930s they brought assamica seed to the Sun Moon Lake basin and set up a dedicated black-tea experiment station in the Yuchi area. For a while the project thrived, and Sun Moon Lake black tea became a recognized export.
After the Second World War, that export trade faded and the region's black tea went quiet for decades, unable to compete on price with cheaper leaf from larger producers. The revival came from two directions late in the century. Taiwan's booming bubble-tea culture created fresh domestic demand for strong local black tea, and in 1999 the Tea Research and Extension Station released Ruby #18. That same year, the powerful 921 earthquake struck Nantou County, causing heavy loss of life and damage across the region; in the rebuilding that followed, the new, high-value cultivar became part of how the lake-side tea communities recovered and re-established their identity. Today the region trades on quality and character rather than volume — a small, named origin rather than a commodity.
The cultivars you will meet
Sun Moon Lake is not a one-plant region, even if Ruby #18 is the headline. A few named cultivars grow side by side around the lake, and knowing them helps you read a label.
| Cultivar | Also called | Character in the cup |
|---|---|---|
| Ruby #18 | Hong Yu, Red Jade, TTES No. 18 | The flagship: sweet, malty and smooth with the signature cool menthol-mint and cinnamon aroma |
| Assam #8 | TTES No. 8 | The older classic: a straight, robust, malty assamica black tea, closer to a traditional breakfast style |
| Hong Yun #21 | Red Rhyme, TTES No. 21 | A newer, more aromatic red-tea cultivar released around 2008, with a fruity, floral-sweet edge |
| Wild mountain tea | Shan cha, var. formosensis | The native parent grown and processed on its own; earthy, brisk and honeyed, made in small amounts |
If a pack simply says "Sun Moon Lake black tea" with no cultivar named, it is most often Ruby #18 or a blend led by it. Assam #8 is the one to seek out if you want the region's older, plainer, more breakfast-like face.
What Sun Moon Lake black tea tastes like
Ruby #18 pours a deep, clear amber-red. The aroma is the giveaway: a cool, almost wintergreen menthol lift wrapped around warm cinnamon and sassafras, unlike anything you meet in an ordinary black tea. The body is where the assamica parent shows — full and rounded, honey-sweet and malty, with ripe fruit (think plum, raisin and fig) and a note people often describe as roasted sweet potato. Crucially, it is smooth: well-made Ruby #18 has very little of the harsh astringency or bitterness that can dog a strong black tea, which is why it is usually enjoyed plain, with no milk or sugar to get in the way of that mint-and-cinnamon signature.
On caffeine it behaves like any true tea: a typical black-tea level, meaningful but generally below a similar-size cup of brewed coffee. Because the leaf is long, dark and whole, it rewards near-boiling water (around 90–95 C / 195–205 F) and takes several infusions before it gives out — each steep unrolls a little more of the aroma. That fully oxidized, no-green-freshness character is exactly what separates it from a grassy green tea; our black tea vs green tea guide walks through why the two taste so different from the same plant.
Sun Moon Lake black tea at a glance
| Feature | Detail |
|---|---|
| Origin | Sun Moon Lake basin, Yuchi, Nantou County, central Taiwan |
| Tea type | Black tea / red tea (fully oxidized), mostly orthodox whole-leaf |
| Elevation | Lake ~750 m; gardens roughly 600–1,000 m |
| Flagship cultivar | Ruby #18 (Hong Yu / Red Jade / TTES No. 18) |
| Ruby #18 parentage | Burmese large-leaf assamica × native wild Taiwan mountain tea (var. formosensis) |
| Signature note | Natural cool menthol-mint and cinnamon aroma |
| Other cultivars | Assam #8 (TTES No. 8), Hong Yun #21 (TTES No. 21), wild mountain tea |
| Liquor | Deep, clear amber-red |
| Flavor | Malty, honey-sweet, ripe fruit and sweet potato; smooth, low astringency |
| Caffeine | Typical black-tea level |
| Best enjoyed | Near-boiling water; plain, no milk; good over several infusions |
How it compares to its neighbours
Set beside other black teas, Sun Moon Lake's gift is that menthol-cinnamon signature, which is genuinely its own. A classic Assam-region black is maltier and more bracing, built for milk; a Yunnan golden-tip red tea leans toward honey, malt and cocoa; a bright Ceylon black is brisker and more citrus-edged. Ruby 18 tea sits apart from all of them because of the cool, almost herbal aromatic that its native parent contributes — you would not confuse the cup for anything else.
Within Taiwan, it is worth placing it against the island's better-known style. Taiwan's international reputation was built on high-mountain oolong — lightly oxidized, floral, grown on cold peaks well above these lake-side gardens. Sun Moon Lake is the opposite pole: a warm, low-basin, fully oxidized red tea. Together they show how much range a single island holds. If you want the map of where black, oolong, green and the rest all fit, our guide to the types of tea lays out the whole six-category picture.
The bottom line
Sun Moon Lake black tea is a small origin with one very big idea. A bred cultivar, Ruby #18, crossed a heat-loving Burmese assamica with a wild native Taiwan plant and came out carrying a natural mint-and-cinnamon perfume that no other black tea owns. Grown in a misty lake basin that was chosen a century ago for its warm, assamica-friendly climate, revived after decades of decline and named for the ruby-red cup it pours, it is proof that a single well-made plant can put a whole region on the tea map. Brew it near-boiling, drink it plain, and let that cool cinnamon aroma tell you where you are.