Du Zhong – 杜仲 Eucommia Bark

Etymology and Name

The name 杜仲 traces back to a legend: classical Chinese texts mention a physician named Du Zhong who was said to have first recorded the medicinal use of this bark. The name persisted. In botanical terms, the plant is called Eucommia ulmoides — from Greek eu (good) + kommi (gum) and Latin ulmoides (elm-like, referring to the leaf shape).

Other designations: In English one encounters „Eucommia bark“, „Chinese gutta-percha bark“ or simply „Du Zhong“. All refer to the same dried bark material.

The Bark: Harvest and Processing

The bark is harvested from Eucommia trees that are at least 10 years old — younger trees yield too little material. Harvest typically takes place in late summer through autumn, when the bark is richest in active constituents.

The most distinctive feature of Du Zhong bark is its thread-pulling inner layer: when a piece of bark is broken or cut, fine white filaments form — these are gutta-percha fibrils, a natural rubber compound. This phenomenon gives the bark its English name „gutta-percha bark“ and serves as a simple quality indicator.

After harvest, the outer cork layer is removed, the bark is dried flat and cut into pieces. The trade distinguishes between raw Du Zhong bark (生杜仲) and a salt-water roasted variant (鹽炒杜仲). For soups and herbal broths, the raw or lightly processed form is typically used. According to PubMed (PMID 29745662), Eucommia ulmoides bark contains lignans, iridoids, phenolics, steroids, terpenoids and flavonoids — a breadth of bioactive compounds whose composition varies by plant part and processing method.

Seasonal Pairings According to TCM

Cantonese herbal cuisine follows a seasonal rhythm — which herbs are combined depends on the time of year and the TCM equilibrium being sought. The Yung family notebooks record the following classical pairings for Du Zhong:

In the Kitchen of the Yung Family

In China Restaurant YUNG’s healing broth — the 黃芪圓肉瘦肉燉湯 (Astragalus-Longan Healing Broth) — Du Zhong plays the role of a quiet supporting voice. At 2 g per portion, it is not the primary flavour carrier, but the element that, in TCM logic, completes the Liver-Kidney dimension of the broth.

Du Zhong is recognisable in the clay pot by its greyish-brown, flat pieces, sometimes with fine white thread remnants at the break edges. Its contribution to the broth is subtle — a slightly bitter, earthy undertone framed by the sweetness of longan and the citrus freshness of Chen Pi. Wai Wah, the founding matriarch of the Yung family, passed this soup down through Cantonese family tradition, embedding it in the restaurant’s menu over decades.

Before cooking, Du Zhong is soaked in cold water for 15 to 20 minutes to soften the bark and allow its aromas to release more readily into the broth. It then goes into the clay pot together with the other dried herbs — at least two hours at low heat.