Garlic does grow underground, but the edible portion is not a true root vegetable like a carrot or a turnip. The part of the Allium sativum plant that is harvested and consumed is botanically classified as a bulb, a specialized storage organ. This bulb develops beneath the soil surface, which leads to the common misconception that it is a root.
The Garlic Bulb: Not a Root, But a Modified Stem
The garlic bulb is fundamentally a modified stem, a type of subterranean structure designed to store nutrients for the plant’s survival. This bulb is composed of several individual segments called cloves, which are actually fleshy, thickened leaves tightly wrapped together. These storage leaves are attached to a small, compressed basal plate at the very bottom of the bulb, which represents the plant’s actual stem.
True roots, which are thin and fibrous, emerge from this basal plate and function only to anchor the plant and absorb water and nutrients from the soil. This anatomical arrangement distinguishes the garlic bulb from a root vegetable, such as a beet, or a tuber like a potato. The whole structure is wrapped in a dry, papery outer layer, known as the tunic, which provides protection against moisture loss and pathogens.
The Process of Underground Bulb Development
The formation of the multi-clove bulb from a single planted clove is a sequential process regulated by environmental cues. Initially, the planted clove sprouts, sending up leaves above ground and establishing a fibrous root system below. For many varieties, particularly hardneck types, the plant must first undergo a period of vernalization, which is exposure to cold temperatures, often around 4°C for several weeks.
This cold period is a biological requirement that signals the plant to switch its internal development and begin forming the bulb itself. After the vernalization requirement is met, the plant needs a long photoperiod, meaning extended hours of daylight, typically 13 hours or more, combined with warmer temperatures to trigger the final bulbing process. Under these conditions, the plant redirects energy from vegetative growth into the lateral buds, which swell and develop into the individual cloves that make up the mature underground bulb.
Harvesting and Curing the Underground Crop
The timing of retrieval and preparation is precise to ensure quality and storage life. Growers watch the foliage above ground for the indication of bulb maturity, typically when the lower leaves begin to yellow and die back. Harvesting should occur when approximately one-third to one-half of the leaves have turned brown, but before the entire stalk collapses, which can cause the bulb wrappers to split and reduce storage quality.
The bulbs must be carefully lifted from the soil, often using a garden fork inserted a safe distance away to avoid damaging the protective skin. Once removed, the bulbs, still attached to their stalks and roots, must be cured in a cool, shady, and well-ventilated location for several weeks. This curing process is a necessary drying step where the outer wrappers shrink and tighten around the cloves, creating a papery, protective shield against moisture and decay organisms for long-term viability.