Acaule

Acaule is a botanical term used to describe plants whose above-ground shoot lacks a conspicuous stem. In acaule species, leaves typically arise directly from a basal crown or rosette at or near soil level, giving the plant a low, compact silhouette. The term is primarily morphological, used in species descriptions and field notes rather than as a taxonomic grouping.

The word derives from Latin a- meaning without and caulus meaning stem, literally “without a stalk.” It is often used interchangeably with acaulescent, though usage can vary by author. The opposite condition is caulescent or cauline, indicating the presence of an above-ground stem.

Acaule plants may have underground stems, bulbs, or tubers from which leaves emerge; the absence of an above-ground stem is mainly a matter of habit, not of overall leaf form. Basal leaves may persist for extended periods, and flowering may occur from the crown via a short peduncle or directly from the base in some species. This habit can be advantageous in certain environments, such as arid or alpine regions, by reducing exposure and water loss and offering protection against grazing.

In flora descriptions, acaule describes many herbaceous perennials and geophytes that form basal rosettes. The term helps distinguish these plants from taller, stemmed relatives and aids in understanding growth form, ecological strategies, and cultivation requirements.