Acaulescence

Acaulescence is the morphological condition in which a plant lacks a true aboveground stem. Acaulescent plants bear leaves that arise from or near the base of the plant, often forming a basal rosette at or near ground level. In such plants the stem is absent or extremely short, so the leaf-bearing axis is not visibly elevated above the ground. The term derives from Greek a- “without” and caulus “stem.”

Acaulescence is common among herbaceous perennials, bulbs, and geophytes that invest in basal foliage rather than an erect flowering stem. Flowering stalks (scapes) may arise from the center of the rosette, sometimes bearing flowers without a tall leafy stem; in other cases flowers are produced directly from the base.

Distribution and examples: It occurs across several plant families, particularly among rosette-forming species, such as Taraxacum (dandelion) in Asteraceae, Narcissus and Tulipa groups in Liliaceae/Asparagaceae, and various Iridaceae and Ranunculaceae members. In cultivated ornamentals, many acaulescent forms are valued for ground cover and a compact habit; examples include some crocus, iris, and bulbous cultivars.

Adaptations and identification: Identification relies on observing leaf arrangement, presence or absence of a distinct aerial stem, and the growth form. Acaulescence is contrasted with caulescence, where a visible stem or culm supports leaves and flowers well above ground. Etymology: from Greek a- “without” and kaulos “stem.”