Iron Skin Dendrobium (Dendrobium officinale Kimura & Migo)

Iron Skin Dendrobium (Dendrobium officinale Kimura & Migo) is a plant in the orchid family, with erect, cylindrical stems that are 9-35 cm long and 2-4 mm thick, unbranched, and with multiple nodes. The leaves are arranged in two rows, papery, lanceolate, with a slight purplish tint on the edges and midrib. The racemes usually emerge from the upper part of old, leafless stems, bearing 2-3 flowers; the bracts are dry, membranous, pale white, and oval, measuring 5-7 mm long. The sepals and petals are yellowish-green, similar in shape, lanceolate, and the lip is white with a green or yellow callus at the base, slightly shorter than the sepals, reflexed in the middle. The column is yellowish-green, about 3 mm long, with a purple spot on each side at the tip; the anther cap is white, long-ovate, triangular, about 2.3 mm long, with a nearly sharp and bifurcated tip. The flowering period is from March to June.

It grows in semi-shady and moist rocky areas at altitudes up to 1600 meters. It is mainly distributed in China’s Anhui, Zhejiang, and Fujian provinces. The stems are used in traditional Chinese medicine as a yin tonic: to nourish the stomach, generate fluids, and clear heat.

Morphological Characteristics

Iron Skin Dendrobium is a herbaceous plant in the orchid family. Its stem is erect, cylindrical, 9-35 cm long, 2-4 mm thick, unbranched, and with multiple nodes. The internodes are 1.3-1.7 cm long, often bearing 3-5 leaves above the middle. The leaves are arranged in two rows, papery, lanceolate, 3-4(-7) cm long, 9-11(-15) mm wide, with a blunt and slightly hooked tip. The base extends downwards into a sheath that wraps around the stem, with edges and midrib often tinged with light purple. The leaf sheaths usually have purple spots, and the upper edge detaches from the stem as they age, leaving a ring-shaped gap.

The racemes usually emerge from the upper part of old, leafless stems, bearing 2-3 flowers. The inflorescence stalk is 5-10 mm long, with 2-3 short sheaths at the base. The inflorescence axis is reflexed and curved, 2-4 cm long. The bracts are dry, membranous, pale white, and oval, 5-7 mm long, with a slightly blunt tip. The pedicel and ovary are 2-2.5 cm long. The sepals and petals are yellowish-green, similar in shape, lanceolate, about 1.8 cm long, and 4-5 mm wide, with a sharp tip and five veins. The lateral sepals are slightly wider at the base, about 1 cm wide. The sepals are conical, about 5 mm long, with a rounded end. The lip is white, with a green or yellow callus at the base, ovate-lanceolate, slightly shorter than the sepals, reflexed in the middle, with a sharp tip, either unlobed or indistinctly 3-lobed, with purplish-red stripes below the middle, and a somewhat wavy margin. The lip disk is densely covered with fine papillae and has a purplish-red spot above the middle. The column is yellowish-green, about 3 mm long, with a purple spot on each side at the tip. The column foot is yellowish-green with purplish-red stripes and sparsely hairy. The anther cap is white, long-ovate, triangular, about 2.3 mm long, with a nearly sharp and bifurcated tip. The flowering period is from March to June.

Propagation Methods

Tissue Culture: Before planting tissue culture seedlings, they should undergo 14-21 days of acclimatization. The seedlings are transferred to an acclimatization room to gradually adapt to the natural environment. Once the leaves turn dark green, they can be planted. Before planting, open the bottle cap and let the seedlings sit in the outdoor air for 2-3 days to adapt to natural temperature and humidity. Then, wash the seedlings, carefully removing them from the culture medium, and rinse off the agar to prevent root rot. Seedlings are sorted by size and quality during the washing process for better cultivation and management, improving survival rates and uniform growth.

Division and Cutting: For division, select 1-2-year-old plants that are tender green, robust, with multiple shoots, well-developed roots, and free from pests and diseases. Remove withered, broken, old branches and overly long roots, then cut the clump into small clusters with 5-7 stems per cluster for planting.

Growth Habits

Iron Skin Dendrobium thrives in cool, moist, and well-ventilated environments. It grows in semi-shady and moist rocky areas at altitudes up to 1600 meters, favoring warm and humid climates and semi-shaded environments but is not frost-tolerant. Wild Iron Skin Dendrobium can withstand temperatures as low as -4.5°C without wilting and has been tested to survive temperatures as low as -9°C.

Geographic Distribution

It is distributed in southwest Anhui (Dabie Mountains), eastern Zhejiang (Yin County, Tiantai, Xianju), western Fujian (Ninghua), northwestern Guangxi (Tian’e), Sichuan, southeastern Yunnan (Shiping, Wenshan, Malipo, Xichou), and southwestern Hunan (Langshan in Xinning County, Shunhuang Mountain in Shaoyang City, Shaodong County).

Current Status

In 1987, the State Council of China listed Iron Skin Dendrobium as a third-grade protected species in the “Regulations on the Protection and Management of Wild Medicinal Resources.” It was included as an endangered plant in the “Red Book of Chinese Plants” in 1992. In 2023, the National Health Commission and the State Administration for Market Regulation included Iron Skin Dendrobium among nine substances traditionally used as both food and medicine.

Medicinal Value

• Taste and Properties: Sweet in taste, slightly cold in nature.
• Functions: Nourishes the stomach and generates fluids; nourishes yin and clears heat; moistens the lungs and benefits the kidneys; improves eyesight and strengthens the waist.

Pharmacological Effects

1. Fluid-Generating Effect: Iron Skin Dendrobium promotes fluid production, primarily by stimulating glandular secretion and organ movement.
2. Blood Sugar Reduction: It can reduce blood sugar levels induced by streptozotocin.
3. Immune System Enhancement: Iron Skin Dendrobium particles (TPSH) can enhance the phagocytic function of macrophages in tumor-bearing animals, promote T-lymphocyte proliferation and differentiation, and increase NK cell activity. It significantly improves serum hemolysin levels in tumor-bearing animals, indicating that TPSH enhances both nonspecific immune function and specific cellular and humoral immune functions.
4. Anti-Skin Aging: In December 2022, researchers at the Kunming Institute of Botany, Chinese Academy of Sciences, discovered a high-content α-mannose-type oligosaccharide (DOMOS) from Iron Skin Dendrobium, which can be used as an exogenous supplement to produce anti-aging effects on the skin both in vitro and in vivo.