Sun Moon Lake Black Tea: Ruby 18, Assam and How to Brew Taiwan's Black Tea

Sun Moon Lake black tea is Taiwan's best-known red tea (hong cha, what the West calls black tea), grown around Sun Moon Lake in Yuchi Township, Nantou County. Two versions matter: Ruby 18 (Hong Yu), a Taiwanese-bred cultivar that tastes of malt, cinnamon, dried fruit and a distinctive cooling mint note; and the older Assam version, which is rounder, maltier and sweeter. It's bold enough for milk but smooth enough to drink straight, with very little bitterness when brewed right. Brew at about 90 °C.

The first sip of Ruby 18 can taste as if someone had put a mint leaf in the cup, though nothing has been added. That cooling, slightly herbal finish is simply what the cultivar does.

Where it comes from#

Sun Moon Lake is a large mountain lake in Nantou County, in the middle of the island. The tea grows on the surrounding hills, mostly in Yuchi Township, at moderate altitude. Red tea was planted here during the Japanese era, when large-leaf Assam bushes were brought in to produce red (black) tea for export. After the export market faded, the area kept making red tea for the local market, and in 1999 Taiwan's tea research station released the Ruby cultivar that made the region famous again.

Ruby 18 vs Assam#

There's also Hong Yun (Red Charm, TTES No. 21), a newer cultivar with a citrus and floral aroma. You'll see it less often, but it's worth a try if you do.

What it tastes like#

Sun Moon Lake vs other red teas#

More in my Chinese red tea guide.

How to brew Sun Moon Lake red tea#

Ruby 18 has a temper: push it with boiling water and long steeps and it turns bitter and astringent. Keep the first steeps short and add time slowly. Cold-brewed, it becomes sweet, minty and almost syrupy; see cold brew tea.

How to buy good Sun Moon Lake tea#

• Cultivar named: Ruby 18 (Hong Yu) or Assam, not just "Taiwan black tea."
• Origin stated: Yuchi or Sun Moon Lake, Nantou. Some shops sell imported red tea blended with local leaf.
• Whole, long, dark leaves with few broken pieces.
• Aroma of cinnamon and malt when you open the pack; a flat, dusty smell means old stock.
• Harvest year on the label.

Storage#

Airtight, dark, cool and away from spices. Red tea keeps well for a year or two, but Ruby 18 loses its bright mint and cinnamon top notes slowly, so it's best drunk within a year. See how to store tea.

Myths#

"Ruby 18 is flavoured with mint or cinnamon." No. Those notes come from the cultivar itself; the mint is entirely the leaf's idea.

"Taiwanese red tea is just Assam grown in Taiwan." The Assam version is, but Ruby 18 is a Taiwanese-bred cultivar with its own character.

"Red (black) tea needs boiling water." Ruby 18 is smoother and sweeter at about 90 °C, and it'll thank you for the restraint.

My honest take#

If you like red tea but find Chinese red teas either too sweet or too smoky, Ruby 18 is worth a try. Its cooling finish makes it one of the easiest red teas to recognise blind. Buy the Assam version if you want a smooth, forgiving milk tea base.

The bottom line#

Sun Moon Lake red tea comes from Yuchi, Nantou. Ruby 18 is malty, spicy and cooling; Assam is rounder and sweeter. Brew at about 90 °C with short steeps, or cold-brew it. More in my Taiwanese tea guide.