Allium

Genus of Amaryllidaceae

Food, Plant source foods, Flowering plats (angiospermae), Mesangiosperms, Monocots, Asparagales, Amaryllidaceae

Consumption area(s): Earth

Note: For better understanding, please read the article on flowering plants (angiospermae) first. If you come across unfamiliar words, you can click on any highlighted term to open the glossary with definitions of key botanical terms.

Introduction

Allium is a vast genus of monocot plants, including nearly one thousand recognized species, which makes it the largest branch of the Amaryllidaceae family and also one of the most extensive genera among flowering plants worldwide. Several species are widely consumed, with a long tradition of domestication and culinary use.

These plants are found mostly in temperate zones across the Northern Hemisphere, though a few species extend into regions like Chile, Brazil, and tropical Africa. Their size ranges greatly, from as little as 5 cm to as tall as 150 cm. Cultivation of different Allium types has taken place since ancient times. Roughly a dozen have gained notable economic relevance as crops or kitchen staples, while a growing number are favored as ornamental plants in gardens.

Members of this genus synthesize distinctive sulfur-based compounds, largely from cysteine sulfoxides, which generate the recognizable garlic-like odor and onion flavor. Although many species serve as edible plants, their taste intensity differs considerably. Usually both the bulbs and the leaves can be eaten. The characteristic pungency of Allium plants depends directly on the sulfur content of the soil. When grown in environments completely lacking sulfates, these plants lose their typical sharpness and become unexpectedly mild.

Description of Allium

Allium plants are herbaceous perennials that survive through true bulbs, sometimes attached to rhizomes, and are easily recognized by their onion-like smell and garlic taste. Their bulbs may appear singly or in clusters and typically regenerate each year from the remains of the older bulbs. In some species, new bulbs arise at the ends of rhizomes or, less commonly, at the tips of stolons. A few species instead develop tuberous roots. The external part of the bulbs are usually brown or gray, with textures that can be fibrous, while the inner part are thin and membranous.

Most alliums grow basal leaves, which often wither progressively from the tip downward before or during flowering, although some retain foliage for longer. The plants bear between one and twelve leaves, generally with linear, flat, or grooved blades. In many species the leaves are straight, though some twist or coil, while a minority produces broader blades. The leaves are sessile, rarely narrowing into a petiole.

The flowers emerge on scapes that are mostly upright, though in certain species they may hang downward. Each flower displays six tepals, arranged in two circles, along with a single style and six stamens attached to the tepals. The anthers and pollen vary in coloration depending on the species. The ovary is positioned superior, divided into three lobes and containing three chambers.

Fruits are formed as capsules, which split lengthwise between the locule walls, releasing rounded, black seeds. The flowering scapes, which may be cylindrical or flattened, usually remain after flowering. The inflorescences are umbels, where the outermost flowers open first and blooming gradually advances inward. These umbels are enclosed by spathe bracts, typically fused and marked with about three veins.

Certain alliums reproduce by generating small offsets near the parent bulb in addition to propagating by seed. Others form numerous bulbils in the inflorescence.

Classification of Allium

This genus is further divided into species, including:

• Allium ampeloprasum (elephant garlic, kurrat, leek, pearl onion, Persian leek)
• Black garlic
• Chives
• Garlic
• Onion (of which shallot is a variety)
• Spring onion