Rotting Grass Transforms into Fireflies: The Philosophy of Metamorphosis and the Earth Virtue of Late Summer in the Great Heat
This article offers a deep reading of Great Heat (Dashu), the twelfth of the twenty-four solar terms, through the lenses of pre-Qin Confucian and Daoist philosophy, classical etymology, and astronomical phenology. It reveals the cosmic significance of the sun reaching ecliptic longitude 120°, when summer heat attains its zenith, and explores the Earth virtue of late summer, the metamorphosis of rotting grass into fireflies, and the hexagram Dun with its two rising yin lines — illuminating the ancient wisdom of reversal at the extreme and counterbalancing excess.
Chapter Twelve: Great Heat and Agriculture — Drought Relief, Flood Drainage, and Field Management
I. "Double Rush" and Agricultural Timing: Racing Against Heaven
Great Heat is one of the most intense periods of agricultural labor. In the southern rice-growing regions, Great Heat coincides with the "double rush" — rushing to harvest the early rice and rushing to transplant the late rice.
Why is Great Heat's agricultural work so urgent$12 Because its high temperatures, humid heat, and frequent rain present both opportunity and challenge. On one hand, high heat and humidity favor rapid crop growth and grain-filling (the transformative power of "moist earth and sultry heat"). On the other, high heat risks drought, heavy rain risks flooding, and humid heat breeds pests and disease. Agriculture at Great Heat is essentially a tense contest of "racing against Heaven."
II. Drought Relief: Responding to the Harm of Excessive Yang
Great Heat's ascendant Fire virtue makes drought — "the harm of excessive yang" — one of the gravest agricultural threats. The Rites of Zhou records the yu sacrifice, a special rain-prayer ceremony.
More profoundly, in the framework of heaven-human resonance, drought (excessive yang) was viewed not only as a natural phenomenon but as a sign of cosmic imbalance, even connected to human maladministration.
III. Flood Drainage: The Double Edge of "Great Rains in Their Season"
Counterbalancing drought, Great Heat's "great rains" can also produce flooding. The Monthly Ordinances' instruction to "burn the weeds and channel the water" — to irrigate and to drain — is the ancients' wisdom for managing Great Heat's rainfall.
This dual task — fighting drought and draining floods simultaneously — profoundly embodies Great Heat's dialectic of "Water and Fire in equilibrium, counterbalancing excess." Water that checks excessive fire is good; but water that becomes excessive is itself a new source of harm. Every "restraining" force also needs to be held in check — balance is dynamic and demands constant adjustment.
IV. Field Management: Weeding, Fertilizing, and Pest Control
Beyond drought and flood, Great Heat is a critical time for field management. The Monthly Ordinances' "burn the weeds and channel the water … manure the fields, enrich the soil" is the ancient template. Great Heat's humid warmth makes weeds grow madly — they must be removed promptly. At the same time, humid warmth maximally accelerates the decomposition of organic matter — making this the ideal time for composting and fertilization.
The essence of Great Heat field management is to exploit the advantages of "moist earth and sultry heat" (composting, accelerating growth) while guarding against its hazards (weeds, pests). This wisdom of "guiding circumstances to advantage while avoiding their harms" is the quintessence of millennia of Chinese agrarian civilization.