The Complete Handbook of Greens

Chapter 1: Understanding Greens

The Biological Baseline: Why Greens Are Different

Every edible green is a perishable, living organ. Unlike a potato or an onion, a leaf does not go dormant. It continues to respire, transpire moisture, and break down its own cellular structure from the moment it is harvested. This is not an abstract biological fact - it is the single most important thing you will ever learn about buying, storing, and handling greens. The entire category is governed by this process, and every practical technique in this book exists to slow it down.

Respiration is the rate at which a plant tissue converts its stored sugars and starches into energy, and it produces heat as a byproduct. A head of iceberg lettuce respires at a rate roughly ten times that of a potato. A bunch of spinach respires faster than most lettuce. Microgreens and sprouts are the most extreme of all - some varieties have respiration rates that produce substantial, measurable heat if they are not cooled quickly. This is why a pallet of warm greens stacked in a loading dock can literally heat itself from the inside, a phenomenon known in the trade as "center heating." You cannot see it from the outside of the pallet, but you will see it two days later when the inner cases arrive with yellow, rotting leaves.

Transpiration is the second process you will manage. Leaves are covered in microscopic pores called stomata, which, on a living plant, are used to