Zingiberaceae

Growth Form and Habit

Perennial herbs arising from fleshy, often aromatic, branched rhizomes (underground stems). Aerial shoots are herbaceous, unbranched or branched, formed either by rolled leaf sheaths (pseudostems) or true stems.

Leaves

Leaves are simple with entire margins, arranged alternately in two distinct ranks (distichous) along the stem. A key feature is the presence of a ligule, a typically membranous or hairy appendage, located at the summit of the open leaf sheath where it joins the leaf blade. The leaf blade usually has a prominent midrib and pinnate-parallel venation. Leaves are often aromatic when crushed.

Inflorescence

Inflorescence structure is often complex and visually striking. It can be a terminal spike, raceme, or thyrse borne on the leafy shoot, or it can arise separately on a leafless stalk directly from the rhizome. Flowers are typically subtended by bracts, which are often large, colorful, closely overlapping, and sometimes fused, forming cone-like or head-like structures (e.g., Zingiber, Curcuma).

Flowers

Flowers are usually bisexual, strongly zygomorphic (bilaterally symmetric), and derived from a 3-merous plan but highly modified. They are often relatively short-lived and fragrant.

• Perianth: Differentiated into calyx and corolla.
  • Calyx: Composed of 3 sepals fused into a tube (synsepalous), usually thin, often splitting down one side, typically inconspicuous. Located atop the ovary.
  • Corolla: Composed of 3 petals fused into a tube below, with 3 lobes above. The dorsal (upper) lobe is typically larger than the two lateral lobes.
• Androecium: Highly modified and petaloid, forming the most conspicuous parts of the flower. Usually only 1 fertile stamen (the median stamen of the ancestral inner whorl) is present, typically with a large anther that may have crests or appendages. The other stamens are sterile and modified:
  • Labellum: Two lateral staminodes of the inner whorl are fused together to form a large, prominent, lip-like structure (the labellum), which often functions as a landing platform for pollinators and is frequently colorful and lobed.
  • Lateral Staminodes: Two lateral staminodes of the outer whorl are either small and tooth-like or petaloid (sometimes large and resembling corolla lobes), or occasionally absent. The median stamen of the outer whorl is always absent.
• Gynoecium: Ovary is inferior, composed of 3 fused carpels, typically forming 3 locules (sometimes reduced to 1). Placentation is usually axile (sometimes parietal or basal). Ovules are usually numerous. A single, long, slender style runs upwards, characteristically passing through a groove or channel in the filament and anther of the fertile stamen. The stigma is usually small, cup-shaped or funnel-shaped, often fringed with hairs, and emerges beyond the anther. Two epigynous nectaries (nectar glands located on top of the ovary) are typically present.

Fruits and Seeds

The fruit is typically a capsule that dehisces loculicidally (splits into the locules) or irregularly, though sometimes it is fleshy and berry-like. The capsule wall can be thin or thick, dry or fleshy. Seeds are usually numerous, rounded or angled, and characteristically possess a brightly colored, often red or orange, fleshy aril (an outgrowth covering part or all of the seed coat), which likely aids in dispersal by birds or other animals.

Chemical Characteristics

The family is defined by its abundance of essential oils and pungent compounds stored in specialized oil cells, particularly in the rhizomes. These include various terpenoids (e.g., zingiberene, cineole), phenylpropanoids, and diarylheptanoids (e.g., gingerols, shogaols in ginger; curcuminoids in turmeric). These compounds contribute to the characteristic aromas, flavors, and medicinal properties of ginger, turmeric, cardamom, etc. Starch is the primary storage carbohydrate in rhizomes.