An old tea plant turns over a colorful new leaf
Though “purple tea” is sometimes marketed as a whole new type of tea in the vein of black or green tea, this name actually refers to the cultivar of tea plant used to make it. There are many purple tea cultivars out there, even just among Chinese teas. The leaves of these plants range from green with a subtle purple tint all the way to rich saturated shades of berry-dark purple-red. Even aside from the well-researched Chinese Zi Juan cultivar, there is a natural diversity of colorful tea trees growing in the forests of Yunnan Province. An estimated 20 to 30 percent of these trees leaf out tinted in colors other than green, such as yellow, white, and of course, purple.
History of purple Chinese teas
Purple leaf plants are found in all families of tea, including the two main subspecies Camellia sinensis var. sinensis and C. sinensis var. assamica, as well as the related ancestor C. taliensis. Some of the more strikingly colored varieties belong to the C. sinensis var. assamica subspecies of the tea tree that grows in Yunnan. The purple plants in this area are most commonly found in the southern and western regions of the province. However, the small-leaf tea bush, C. sinensis var. sinensis, produces its own purple members as well. The green tea Gu Zhu Zi Sun (Purple Bamboo Shoot) was named for the faint purple blush of its youngest leaves. This former tribute tea has a very long history dating back to the Tang Dynasty (618-907). Tea plants with oddly colored leaves are nothing new.
Until recently, though, purple leaf plants in Yunnan were largely ignored by tea makers, let alone consumers. Some producers even go as far as to request their exclusion from the harvest, having noticed that the darker-than-usual leaves make a noticeable difference in the flavor of the tea. Of course, local people of the many ethnic minorities living in Yunnan have long been aware of zi cha “purple tea,” since they are the ones who own, care for, and harvest the highly-prized old growth tea trees that typically produce it in their tea gardens and the surrounding mountain rainforests. The broader interest in making tea from purple leaf plants in particular is a recent thing. Intensely purple cultivars have been developed in China, Kenya, India, and Japan and are now appearing on the market for consumption.
The original purple leaf trees in Yunnan display the purple coloration only in the youngest leaves of new growth. If allowed to grow to maturity, the purple leaves will fade to green again. Because of this, they’re also called zi ya (“purple buds”) by locals. They are known to grow most commonly under two conditions: at high altitudes, and on older tea plants. Though the young leaves are dark enough to be quite distinct from your average green tea leaf, they are typically not as deep purple as super-dark cultivars like second-generation Zi Juan.
In China, tea scientists first learned of purple-leafed tea trees growing in the Nannuo Mountains in the Menghai area in southern Yunnan, near the famous tea-producing region of Xishuangbanna in the 1950s. The darkest of these was the original Zi Juan variety, which fully displays the reddish-purple coloration on the first 4-5 leaves and even on the stem of the new growth. This rare variety was poetically named “Zi Juan” after a beloved character from the Chinese classic Dream of the Red Chamber, whose name includes the character zi 紫 for “purple.” Teas like our Zi Juan Chun Cha (Purple Spring Tea), Zi Juan Gong Ting (Purple Leaf Palace Puer), and Zi Ye Shu (Purple Leaf Shu Puer) are made from these traditional variety trees. Other teas like our Hei Tiao Zi (Black Stripe) are made from a slightly lighter purple variety, which only shows purple on the youngest 2-3 leaves and has regular green stems.
The development of intense purple cultivars began in 1985, when researchers took cuttings from these Zi Juan Camellia sinensis var. assamica trees in the forest and began growing them at the Yunnan Academy of Agricultural Sciences Tea Institute. Through a process of propagating and backcrossing these cuttings, they were able to selectively breed tea plants with a much more concentrated dark purple color. This new second-generation cultivar was also named Zi Juan after the original trees.
The rise of purple leaf puer
The Zi Juan cultivar produces buds that are a much darker purple than its forebears, even in the younger plants. Not only that, but a noticeable purple coloring persists even in the mature leaves, and the difference is obvious when placed side by side with a green tea plant. Like the ancestral purple leaf plants, this cultivar is particularly rich in the anthocyanins that cause the coloration. These flavonoid antioxidants have been highly touted for many health benefits, including their support of the immune system.
Puer cakes made exclusively from purple leaves are quite a new development. Our Jing Mai Teng La Zi Juan (Purple Tea Buds) and Zi Juan (Purple Tea Leaves) sheng puer cakes are made entirely from the leaves of the original Zi Juan variety. Since we first began seeing these purple cakes in 2006, enthusiasm for purple leaf teas has spread across continents.
In China, most purple leaves of any origin are still used to make sheng puer tea cakes as per tradition. However, as puer ripening techniques improve, some producers are starting to make shu puer with them. In Kenya, much of the purple leaf crops grown there are made into black tea, and the Japanese “Sunrouge” cultivar is processed as a green.
Genetics and environmental factors
People originally thought that the production of purple leaves was dependent on soil conditions. However, scientists have since discovered that this trait has a heritable genetic basis that is also affected by environmental conditions. In the Zi Juan cultivar, the purple coloration is produced by the upregulation of a transcription factor that helps control the levels of anthocyanins present. Exposing the plant to cooler temperatures and longer periods of light exposure seems to encourage the upregulation of this transcription factor. This leads to greater accumulation of anthocyanins in the leaves, turning them darker purple. These findings corroborate the traditional knowledge that purple leaf plants are found at higher elevations, where the temperatures are colder.
Many of these cultivars are developed not only for color, but for resistance to agricultural stresses like drought, pests, and temperature extremes. The production of extra anthocyanins appears to originally be one of the plant’s responses to such conditions, helping them survive such environmental challenges. If the high levels of anthocyanins make the plants better adapted to survive in our ever more unpredictable climate, it’s possible that purple cultivars will become quite valuable to tea farmers for more reasons than just their aesthetic, nutritional, and gastronomic qualities.
In the end, purple leaf tea is another one of those many cases where a natural variation is cultivated by humans and taken to an extreme. People have made tea using purple plants for thousands of years. However, intense purple cultivars like Zi Juan have only arisen in the past thirty years. It’s yet to be seen whether they will become more widely recognized and available, or remain a colorful oddity enjoyed only by the tea enthusiasts who seek them out.
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