Kadua centranthoides is an erect to sprawling subshrub that can grow from 30 to 200 cm tall. The stems are cylindrical, either glabrous or short-hirtellous, especially in the inflorescence, and often exhibit a glaucous appearance. The leaves are simple and opposite, typically spaced widely apart. These leaves can range from narrowly to broadly ovate, cordate, or oblong-ovate to oblong-lanceolate, measuring between 4 to 16.5 cm long and 1 to 5.5 cm in width. The leaf apex may be acuminate to long acuminate, occasionally extending to caudate, with a cordate base to subcordate. The leaf surfaces are generally glabrous, though the lower surfaces might be short hirtellous along the midrib and sometimes more extensively along the veins. The leaf blades are firm to coriaceous with entire margins. The lateral veins are typically impressed on the upper surface and raised on the lower surface. The flowers appear stiff, usually narrow, decussate, interrupted, thyrsoid paniculate inflorescences, with lateral branches ending in compact or sometimes loose cymes. These inflorescences can be glabrous or hirtellous throughout. The flowers are insect-pollinated and can be bisexual (perfect) or functionally pistillate. The calyx lobes are narrowly deltate to oblong, ranging from 1 to 3.5 mm long, and may be glabrous or short-hirtellous. The corolla is purple to violet with a green to yellowish green throat, fleshy, and salverform, with a tube 9 to 20 mm long. The corolla lobes are 3 to 7 mm long and typically reflexed. The fruit is a turbinate to subglobose capsule, slightly compressed and strongly grooved, measuring 3 to 5 mm long and 3.5 to 7 mm in diameter. It dehisces loculicidally across the disk, with the pyrenes separating septicidally but remaining within the persistent vascular skeleton of the mesocarp. The seeds are pale brown, irregularly cuneiform, strongly compressed, conspicuously winged, and minutely rugulose, featuring well-developed oily endosperm or occasionally scant or absent endosperm. It inhabits open areas in wet forests and margins of bogs, occasionally found in mesic forests between 380-1920 meters.