Harveya speciosa produces dense racemes of large, creamy-white flowers. The flower is trumpet-shaped with a yellow throat. The calyx tube is green or reddish with short lobes.
The corolla tube is creamy green and hairy on the outside, about 6 cm in length. The corolla is deeply five-lobed with uneven, wavy, rounded lobe margins. The flower shape deviates slightly from radially symmetrical by being elongated vertically. The flowers are fragrant at night, attractive to pollinators that feed after dark (Manning, 2009).