Lythrum Explained

Lythrum is a genus of 38 species of flowering plants native to the temperate world. Commonly known as loosestrife (a name they share with Lysimachia, which are not closely related), they are among 32 genera of the family Lythraceae.^[1]

Description

They are herbaceous annuals or perennials. Typically they have square stems, narrow stalkless leaves, and spikes of star-shaped flowers in shades of purple, pink and white. They are especially associated with boggy areas, river banks and ponds, though in cultivation they often tolerate drier conditions. The species L. salicaria (purple loosestrife) and L. virgatum are found in cultivation.^[1]

Selected species

Species include:^{[2] [3] [4]}

Lythrum alatum Pursh  - winged lythrum Lythrum anceps (Koehne) Makino  - misohagi (Japan) Lythrum californicum Torr. & A.Gray  - California loosestrife Lythrum curtissii Fernald  - Curtiss' loosestrife Lythrum flagellare Shuttlw. ex Chapm.  - Florida loosestrife Lythrum hyssopifolia L.  - hyssop loosestrife, grass-poly Lythrum junceum Banks & Sol.  - false grass-poly Lythrum lineare L.  - wand lythrum

Lythrum maritimum Kunth  - pūkāmole (Peru, Hawaii) Lythrum ovalifolium Koehne  - low loosestrife Lythrum portula (L.) D.A.Webb  - spatulaleaf loosestrife, water purslane Lythrum salicaria L.  - purple loosestrife Lythrum thymifolia L.  - thymeleaf loosestrife Lythrum tribracteatum Salzm. ex Spreng.  - threebract loosestrife Lythrum virgatum L.  - European wand loosestrife Lythrum wilsonii Hewson  - Wilson's loosestrife

Formerly placed here

• Cuphea carthagenensis (Jacq.) J.F.Macbr. (as L. carthagenense Jacq.)
• Cuphea melanium (L.) R.Br. ex Steud. (as L. melanium L.)
• Cuphea parsonsia (L.) R.Br. ex Steud. (as L. parsonsia L.)
• Cuphea racemosa subsp. racemosa (as L. racemosum L.f.)
• Cuphea viscosissima Jacq. (as L. petiolatum L.)
• Pleurophora anomala (A. St.-Hil.) Koehne (as L. anomalum A.St.-Hil.)
• Woodfordia fruticosa (L.) Kurz (as L. fruticosum L.)^[5]

Morphology

Some species of Lythrum are heterostylous, such as the tristylous (occurring in three forms) L. salicaria.^[6]

Ecology

Lythrum species are used as food plants by the larvae of some Lepidoptera species, including the small emperor moth, the engrailed, the Hebrew character, and the V-pug.

As a noxious weed in the United States

The genus Lythrum is listed as a noxious weed in Michigan, North Carolina, and Wisconsin.^[7]

Fossil record

So far the oldest evidence of Lythrum is fossil pollen from the early Campanian, 82-81 Ma of Wyoming.^[8]

Notes and References

1. Book: RHS A-Z Encyclopedia of Garden Plants. 2008. Dorling Kindersley. United Kingdom. 978-1405332965. 1136.
2. http://plants.usda.gov/core/profile?symbol=LYTHR Lythrum L.
3. Common name for L. junceum Web site: Lythrum junceum (false grass-poly) . Flora of Derbyshire. February 15, 2007 . Derby City Council and Derbyshire Flora Committee . February 26, 2010.
4. Common name for L. wilsonii Web site: Innamincka Regional Reserve - Flora Species List (By Family) . National Parks and Wildlife South Australia, Department for Environment and Heritage . February 26, 2010 . dead . https://web.archive.org/web/20091025110323/http://www.environment.sa.gov.au/parks/pdfs/INNAMINCKA_RR_FAMILY.PDF . October 25, 2009 .
5. Web site: GRIN Species Records of Lythrum . Germplasm Resources Information Network . United States Department of Agriculture . 2011-02-19.
6. Eckert, C. G.. Frequency-dependent selection on morph ratios in tristylous Lythrum salicaria (Lythraceae) . Heredity . 1996 . 77 . 6 . 581–88 . 10.1038/hdy.1996.185 . 23567206 . etal. free .
7. Web site: Plants Profile for Lythrum alatum (winged lythrum) . plants.usda.gov . 31 January 2018 . .
8. Graham, Shirley A. “Fossil Records in the Lythraceae.” Botanical Review, vol. 79, no. 1, 2013, pp. 48–145., www.jstor.org/stable/41809868. Accessed 20 Sept. 2020.