Solar Terms and TCM: Growing and Harvesting in Harmony with Nature

The twenty-four solar terms (二十四节气) not only guided agricultural life in ancient China but also profoundly influenced the growth, care, and harvesting of Traditional Chinese Medicinal herbs. TCM emphasizes the concept of “harmony between humans and nature,” recognizing that the growth of medicinal plants is affected by climate, sunlight, temperature, humidity, and soil conditions, all of which change in accordance with the solar terms. Understanding the relationship between solar terms and herb growth is not only an ancient wisdom but also an important foundation for modern quality control of medicinal herbs.


Solar Terms and the Growth Rhythm of Medicinal Herbs

Spring: Germination and Growth

  • Lichun 立春 – Guyu 谷雨
  • Spring brings rising yang energy and warming temperatures, the period when most herbs sprout and grow fastest. 
  • Aromatic herbs such as Bo He (薄荷, mint), Ju Hua (菊花, chrysanthemum), Zi Su Ye (紫苏叶, perilla leaf) thrive under moderate sunlight and temperature.

  • Wild herbs often return to green at this time and require proper watering and soil loosening to support healthy growth.

Summer: Vigorous Growth and Accumulation

  • Lixia 立夏 – Dashu 大暑
  • With this time’s abundant sunlight, plants achieve peak photosynthesis, allowing medicinal compounds to accumulate efficiently.

  • Root herbs like Huang Qin (黄芩, scutellaria), Ban Lan Gen (板蓝根, isatis root), and Huang Lian (黄连, coptis) accumulate the most active constituents during this season.

Autumn: Consolidation and Maturity

  • Liqiu 立秋 – Shuangjiang 霜降
  • The cool and dry autumn conditions are ideal for root and rhizome herbs to reach maximum potency.

  • Root and rhizome herbs such as Dang Shen (党参, codonopsis), Bai Zhu (白术, atractylodes), Dan Shen (丹参, salvia), and Chuan Xiong (川芎, ligusticum) are usually harvested around Shuangjiang for optimal efficacy. 

  • Leaf and flower herbs typically complete their growth cycles by early autumn.

Winter: Dormancy and Preservation

  • Lidong 立冬 – Dahan 大寒
  • Plants enter dormancy during the wintertime, but roots still carry out minimal metabolism underground.

  • Cold-resistant herbs such as Fu Zi (附子, aconite) and Tian Ma (天麻, gastrodia) undergo a “refinement” process in low temperatures, enhancing active compounds.

  • Winter is also the key time to prepare the soil and apply base fertilizers for the next year’s planting.

Solar Terms and Optimal Harvesting Time

The concentration of active compounds in herbs is closely tied to the harvest season. Ancient farmers summarized: “Harvest flowers at bloom, leaves at peak growth, roots in autumn or winter, and fruits when ripe.” Modern pharmacological studies support these practices.

Flowers

  • Ju Hua (菊花, chrysanthemum), Mei Gui Hua (玫瑰花, rose), Jin Yin Hua (金银花, honeysuckle) are harvested between the Summer Solstice (Xiazhi 夏至) to the Great Heat (Dashu 大暑), preferably in the early morning when fragrance and essential oil content are highest.

Leaves

  • Sang Ye (桑叶, mulberry leaves) and Bo He (薄荷, mint) are harvested from Xiaoman (小满) to Summer Solstice (Xiazhi 夏至), when vitality and active constituents are at their peak.

Roots and Rhizomes

  • Dan Shen (丹参, Salvia), Huang Qi (黄芪, Astragalus), Bai Zhu (白术, Atractylodes), Dang Shen (党参, Codonopsis) are harvested from Autumn Equinox (Qiufen 秋分) to Shuangjiang (霜降), when above-ground parts have withered and nutrients become concentrated in the roots.

Fruits and Seeds

  • Shan Zha (山楂, hawthorn), Gou Qi Zi (枸杞, goji berries), and Wu Wei Zi (五味子, Schisandra) are harvested from Bailu (白露) to Shuangjiang (霜降), where farmers select fruits that are bright, plump, and rich in sugar or acids.

Solar Terms and Quality Control of Medicinal Herbs

Modern cultivation and harvesting of medicinal herbs still follow traditional solar term guidelines for several reasons:

1. Active compounds fluctuate with the climate: For example, Dan Shen contains about 20% more active ingredients when harvested in autumn than in summer.

2. Solar terms influence pest and disease risks. Targeted field management, which tends to follow seasonal patterns, reduces pesticide residues.

3. Standardized harvesting ensures consistent quality. Famous regional herbs like Chuan Xiong (川芎), Huai Dang Shen (淮党参), and An Guo Ju Hua (安国菊花) rely on precise timing to maintain their unique qualities.

Solar terms (二十四节气) are not only markers of seasonal change but also natural “clocks” for the growth of medicinal herbs. Planting and harvesting in harmony with these rhythms ensures high-quality, pure, and effective herbs. For TCM practitioners, understanding the relationship between solar terms and herbs is crucial not only for maintaining clinical quality but also for embodying the TCM principle of “harmony between humans and nature.”