Harvest Timing Against Market Timing: Quality-Loss Bounds for Morning-of and Evening-Before Harvest of Leafy Greens, and a Rule for When Each Wins

Leafy greens for a morning market are cut either the evening before or early on the market day itself. The evening cut spreads labour; the morning cut is fresher but demands pre-dawn work. This paper puts computed bounds on the quality difference and derives a rule for choosing. Quality retained is exp(−A), where A is the integral of a temperature-dependent decay rate from harvest to the time of interest. Three routes are computed across daytime temperatures of 20, 25, 30, and 35 °C: evening-before at ambient overnight (15 hours to opening), evening-before in an 8 °C cool box (15 hours), and morning-of harvest (2.5 hours). At opening, morning-of retains 0.9576, 0.9339, 0.8974, and 0.8428 across those days — a loss of 4.2 to 15.7 percent. Evening-before at ambient retains only 0.7707, 0.6624, 0.5214, and 0.3571 — a loss of 22.9 to 64.3 percent. The cool box retains 0.8608 on every day, because its temperature does not depend on the weather. Two thresholds are originated. On quality alone, cooled evening ties morning-of when the temperature at the morning harvest reaches 27.6 °C. On total penalty per bunch — quality loss valued at the $3.00 price, plus $0.18 per bunch early-labour premium for the morning route and $0.07 for cool-box handling — the two routes tie on a 30 °C day, each at $0.488, with the morning route cheaper below that temperature and the cool box cheaper above it. Ambient evening harvest, despite no extra cash cost, carries the largest penalty at every temperature, reaching $1.929 per bunch on a 35 °C day. The rule is: do not rely on an ambient overnight hold in warm weather; choose between a morning cut and a cooled evening cut by which side of roughly 30 °C the day sits.