Aquatic and Wetland Vascular Plants of the Northern Great Plains
Lythraceae - The Loosestrife Family
Annual or perennial herbs, sometimes woody at the base. Leaves simple, entire, opposite or both opposite and alternate or rarely some whorled, sessile or nearly so, exstipulate. Flowers single or few clustered in leaf axils or in terminal, bracteate, spikelike inflorescences, subsessile or short-pedicelled, subtended by a pair of small bracteoles on the pedicels, these sometimes deciduous with age. Flowers perfect, regular or somewhat irregular, often di- or trimorphic with respect to stamen and style lengths; calyx tubular, cylindrical or campanulate to globose, strongly nerved, the calyx lobes 4 or 6, alternating with longer appendages in the sinuses between the lobes; petals 4 or 6, separate, pink or purple, crumpled, deciduous; stamens numbering as many as or 2X (rarely to 3X) as many as the petals; stigma capitate, style simple, slender, ovary superior, free of the calyx tube or cup. Fruit a many-seeded capsule.
| Lead | Characteristic | Go To |
| 1 | Flowers 4-merous, axillary; calyx tube campanulate to globose; plants annual. | Lead 2 |
| 1 | Flowers 6-merous, in terminal, bracteate, spikelike inflorescences; calyx tube cylindrical; plants perennial. | Genus Lythrum |
| 2 | Leaves of middle and upper stem attenuate at the base; flowers solitary in the axils. | Genus Rotala |
| 2 | Leaves of middle and upper stem auriculate or cordate and clasping at the base; flowers (1)3-many in the axils. | Genus Ammannia |
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