4. Lysimachia L. (loosestrife)

Plants perennial herbs, often with rhizomes, stolons, or offsets. Stems erect or ascending, or prostrate, branched or unbranched. Leaves opposite or whorled (the lowermost leaves sometimes merely subopposite in L. vulgaris), sessile or petiolate, the petiole sometimes flattened and fringed along the margins. Leaf blades unlobed, variously linear to circular, the margins entire, the surfaces sometimes gland-dotted (the dots sometimes slightly sunken into the tissue, the structure then termed punctate). Inflorescences of axillary, solitary flowers or of terminal and/or axillary racemes, these occasionally appearing paniculate. Flowers long-stalked. Calyces (4)5–7-lobed nearly to the base, the lobes spreading or arched outward. Corollas saucer-shaped to bell-shaped, the tube very short, the lobes spreading or arched outward, yellow (white elsewhere), sometimes with reddish purple markings on the upper surface near the base and/or along the margins, often densely glandular on the upper surface near the base, sometimes with small reddish purple to dark red or nearly black dots or lines on 1 or both surfaces. Stamens 5, the filaments attached at the corolla base, sometimes also fused into a short basal tube, the anthers yellow. Staminodes sometimes present, 5, alternating with the stamens, membranous or scalelike, narrowly lanceolate to nearly triangular. Ovary superior, with few to many ovules, the style slender, the stigma capitate. Fruits capsules, ovoid to globose, dehiscent longitudinally by 5 valves, the style usually persistent on 1 of the valves. Seeds few to many, often angular. About 200 species, nearly worldwide.

The flowers of Lysimachia have an interesting pollination syndrome. The flowers of several species are visited by bees in the genus Macropis. The bees collect the pollen, and the females harvest the secretions produced by the glandular trichomes on the inner surface of the petals and on the filaments (Simpson et al., 1983). Coffey and Jones (1980) reported that species in the subgenus Seleucia Bigelow are self-incompatible, and that interspecific crosses within subgenus Seleucia are fertile. However, Simpson et al. (1983) observed that at least some individuals of L. ciliata were found to be self-fertile, and suggested that the incompatibility system might vary geographically or with ploidy level.

Three of the five subgenera of Lysimachia are recognized by J. D. Ray (1956) are represented in Missouri. In the past, each has, at times been treated as a separate genus. The largest of these is subgenus Seleucia, a group of species with staminodes alternating with the stamens, petals that each enclose a stamen in the bud, and leaves that are not gland-dotted. Included in this subgenus are L. ciliata, L. lanceolata, L. hybrida, L. quadriflora, and L. radicans. Subgenus Lysimachia, represented in Missouri by L. nummularia, L. terrestris, and L. vulgaris, is a group that lacks staminodes and has leaves that are gland-dotted. Subgenus Naumbergia (Moench) Hand.-Mazz., containing only L. thyrsiflora, has unique, long-stalked, short, dense racemes produced from the median leaf axils.

In addition to the species treated below, two other species of Lysimachia bear mention in the present account. Lysimachia clethroides Duby (gooseneck loosestrife; a member of the Old World subgenus Pallida (Moench) Hand.-Mazz.) is native to Asia, but is cultivated in the United States, both as an ornamental and as a bee plant. This taxon is strongly colonial from long-creeping, branched rhizomes and differs from other species of Lysimachia in Missouri in its alternate leaves, strongly arched, terminal racemes, and white corollas. It has not yet been recorded as an escape in Missouri, but has become naturalized widely in the northeastern United States, including four states adjoining Missouri: Iowa, Illinois, Kentucky, and Tennessee. Many gardeners learn to their dismay that this species is very aggressive in gardens and in some states it is considered an invasive exotic.

On the other hand, L. quadrifolia L. (whorled yellow loosestrife; subgenus Naumbergia) is a native wildflower that is widespread in the eastern United States and adjacent Canada, west to Minnesota, Illinois, and Alabama. It has been collected several times in Missouri, all from a single woodland site at the Shaw Nature Reserve (Franklin County) and in each case the collector thought that it was a native taxon. However, data in the Missouri Botanical Garden’s archives indicates that former Garden director, Edgar Anderson, planted a small colony at this site sometime during the 1940s. Plants have continued to persist, but there is no evidence that the population is growing or spreading. In Steyermark’s (1963) treatment, L. quadrifolia keys imperfectly to either L. hybrida or L. ciliata (both subgenus Seleucia), but in fact, the species is more closely related to L. nummularia and L. vulgaris (both subgenus Lysimachia) by virtue of its gland-dotted leaves and flowers lacking staminodes. It is a rhizomatous perennial with ascending stems, leaves mostly in whorls of 4, and flowers that are solitary from some of the leaf axils.