Houstonia longifolia, commonly known as long-leaved bluet or longleaf summer bluet, is a perennial plant in the family Rubiaceae. It can be found throughout most of the Eastern United States and Canada. It has been reported from every state east of the Mississippi River except Delaware, plus North Dakota, Minnesota, Missouri, Arkansas and Oklahoma, with isolated populations in Kansas and Texas. Also, all Canadian provinces from Quebec to Alberta. It prefers upland woods in poor, dry, often sandy soil.
It has upright stalks of 20 centimetres (8 in) or sometimes taller, rising from a basal rosette of leaves. The stalks are slender and branching, with small white flowers with 4 petals. The basal rosette of leaves withers away before the flowers bloom, and opposite leaves appear at intervals along the stems. Flowers bloom for about a month in late spring and summer. It prefers full or partial shade and dry or mesic conditions.
Two varieties are recognized:
- ^ a b c Kew World Checklist of Selected Plant Families
- ^ Gaertner, Joseph. 1788 De Fructibus et Seminibus Plantarum: accedunt seminum centuriae quinque priores cum tabulis Aeneis LXXIX. Stutgardiae, Tubingae 1: 226
- ^ Biota of North America Program
- ^ Gleason, Henry A.; Cronquist, Arthur (1991). Manual of Vascular Plants of Northeastern United States and Adjacent Canada (second ed.). ISBN 978-0893273651.
- ^ Denison, Edgar (2017). Missouri Wildflowers (Sixth ed.). Conservation Commission of the State of Missouri. p. 22. ISBN 978-1-887247-59-7.
- ^ "Long-Leaved Bluets (Houstonia longifolia)". www.illinoiswildflowers.info.
- USDA PLANTS Profile
- Photo of herbarium specimen at Missouri Botanical Garden, isotype of Houstonia longifolia