What are the propagation methods for the Chinese medicinal herb Dendrobium?
Dendrobium, also known as diaolan, is a perennial herbaceous plant of the orchid family and a precious Chinese medicinal herb; it is divided into Dendrobium nobile, Dendrobium officinale, Dendrobium chrysotoxum, Dendrobium fimbriatum and Dendrobium loddigesii, and Dendrobium officinale is called the “first of China's nine great immortal herbs”.
Dendrobium is used medicinally as fresh stems or dried stems, and has the functions of benefiting the stomach and promoting fluid production, and nourishing yin and clearing heat; it is mostly used for symptoms such as damage to yin with depletion of fluids, dry mouth and excessive thirst, poor appetite and dry retching, deficiency heat after illness, and blurred vision; it is also a sacred medicine widely used in traditional Chinese medicine from ancient times to the present for treating various syndromes of kidney yin deficiency.
Dendrobium is not only increasing in dosage in domestic clinical formulations of traditional Chinese medicine, but is also in great demand for export sales and as an industrial raw material for Chinese patent medicines, with an annual demand of 800,000 to 1,000,000 kg.
The propagation methods of Dendrobium are divided into two major categories: sexual propagation and asexual propagation. At present, asexual propagation is mainly used in production.
Sexual propagation: Dendrobium seeds are extremely small, with about 20,000 seeds per capsule, appearing as a yellow powder. They usually do not germinate, and can only sprout and grow under environmental conditions with sufficient nutrients, suitable humidity and moderate light. Generally, they need to be cultured in a tissue culture room.
Asexual propagation is divided into three types. The first is division propagation: carried out in spring and autumn, preferably before Dendrobium sprouts at the end of March or the beginning of April. Select 1- to 2-year-old plants with good growth, no pests or diseases, well-developed root systems and many sprouts as stock plants, pull them up by the roots, remove dead branches and broken branches, cut off excessively long fibrous roots, keep old roots at about 3 cm, and divide them into several clumps according to the number of stems. Each clump must have 4-5 stems and can then be used as seed stems.
The second is cutting propagation: carried out in spring or summer, preferably in May to June. Select robust 3-year-old plants, take their plump and rounded stem segments, keep 4-5 nodes per segment, about 15-25 cm long, insert them into limestone or river sand, with the depth such that the stem does not fall over, and wait until the axillary buds on the stems sprout and white aerial roots grow, then they can be transplanted. Generally, when selecting materials, the upper stem segments are mostly used, because they have apical dominance, so the survival rate is high, the number of sprouts is large, and growth and development are fast.
The third is high-bud propagation: mostly carried out in spring or summer, mainly in summer. On Dendrobium plants more than 3 years old, axillary buds (also called high buds) sprout on the stems every year and grow aerial roots, becoming small seedlings. When they grow to 5-7 cm, they can be cut off and transplanted.